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  • Neutrino mass generation with large $SU(2)_L$ multiplets under local $U(1)_{L_\mu - L_\tau}$ symmetry
    KIAS-P18040
    KIAS-P18040
    arXiv:1805.03942

    by: Nomura, Takaaki
    Abstract:
    We propose a model of neutrino mass matrix with large $SU(2)$ multiplets and gauged $U(1)_{L_\mu - L_\tau}$ symmetry, in which we introduce $SU(2)$ quartet scalar and quintet fermions with nonzero $L_\mu - L_\tau$ charge. Then we investigate the neutrino mass structure and explore phenomenologies of large multiplet fields at the collider, particularly, focussing on doubly- and singly- charged exotic leptons from the quintet.

  • Matter effects in neutrino visible decay at future long-baseline experiments
    arXiv:1805.03279

    by: Ascencio-Sosa, M.V.
    Abstract:
    Neutrino visible decay in the presence of matter is re-evaluated. We study these effects in two future long-baseline experiments where matter effects are relevant: DUNE (1300 km) and a hypothetical beam aimed towards ANDES (7650 km). We find that matter effects are negligible for the visible component of neutrino decay at DUNE, being much more relevant at ANDES. We perform a detailed simulation of DUNE, considering $\nu_\mu$ disappearance and $\nu_e$ appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant $\alpha_3$ can be as low as $2\times10^{-6}$ eV$^2$ at 90% C.L., depending on the neutrino masses and type of coupling. We also show the impact of neutrino decay in the determination of $\theta_{23}$ and $\delta_{\rm CP}$, and find that the best-fit value of $\theta_{23}$ can move from a true value at the lower octant towards the higher octant.

  • Leptonic Dark Matter with Scalar Dilepton Mediator
    UCRHEP-T591 (May 2018)
    UCRHEP-T591-(MAY-2018)
    arXiv:1805.03295

    by: Ma, Ernest
    Abstract:
    A simple and elegant mechanism is proposed to resolve the problem of having a light scalar mediator for self-interacting dark matter and the resulting disruption to the cosmic microwave background (CMB) at late times by the former's enhanced Sommerfeld production and decay. The crucial idea is to have Dirac neutrinos with the conservation of U(1) lepton number extended to the dark sector. The simplest scenario consists of scalar or fermion dark matter with unit lepton number accompanied by a light scalar dilepton mediator, which decays to two neutrinos.

  • Towards the minimal seesaw model for the prediction of neutrino CP violation
    arXiv:1805.02925

    by: Shimizu, Yusuke
    Abstract:
    We discuss the minimal seesaw model for the Dirac CP violating phase of the lepton mixing matrix. We introduce two right-handed Majorana neutrinos and obtain several textures of the tri-maximal lepton mixing matrices. Moreover, we discuss the observed baryon asymmetry of the universe through the leptogenesis mechanism. As the result, we obtain the specific model which predicts the negative sign of maximal Dirac CP violating phase and normal hierarchy of neutrino masses.

  • The EDGES signal: An imprint from the mirror world?
    arXiv:1805.02685

    by: Aristizabal Sierra, D.
    Abstract:
    Recent results from the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) show an anomalous spectral feature at redshifts $z\sim 15-20$ in its 21-cm absorption signal. This deviation from cosmological predictions can be understood as a consequence of physics that either lower the hydrogen spin temperature or increases the radiation temperature through the injection of soft photons in the bath. In the latter case, standard model neutrino decays $\nu_i \to \nu_j\,\gamma$ induced by effective magnetic and electric transition moments ($\mu_\text{eff}$) are precluded by the tight astrophysical constraints on $\mu_\text{eff}$. We show that if mirror neutrinos are present in the bath at early times, an analogous mechanism in the mirror sector can lead to a population of mirror photons that are then "processed" into visible photons through resonant conversion, thus accounting for the EDGES signal. We point out that the mechanism can work for mirror neutrinos which are either heavier than or degenerate with the standard model (SM) neutrinos, a scenario naturally realized in mirror twin Higgs models.

  • Neutrino Signatures in Primordial Non-Gaussianities
    arXiv:1805.02656

    by: Chen, Xingang
    Abstract:
    We study the cosmological collider phenomenology of neutrinos in an effective field theory. The mass spectrum of neutrinos and their characteristic oscillatory signatures in the squeezed limit bispectrum are computed. Both dS-covariant and slow-roll corrections are considered, so is the scenario of electroweak symmetry breaking during inflation. Interestingly, we show that the slow-roll background of the inflaton provides a chemical potential for the neutrino production. The chemical potential greatly amplifies the oscillatory signal and makes the signal observably large for heavy neutrinos without the need of fine tuning.

  • $Z'$ Portal Dark Matter in $B-L$ Scotogenic Dirac Model
    arXiv:1805.02025

    by: Han, Zhi-Long (Jinan U.) et al.

    Abstract:
    In this paper, we perform a detail analysis on the phenomenology of $Z'$ portal scalar and Dirac fermion dark matter in $B-L$ scotogenic Dirac model. Unconventional $B-L$ charge $Q$ is assigned to the right-handed neutrino $\nu_R$ in order to realise scotogenic Dirac neutrino mass at one-loop level, where three typical value $Q=-\frac{1}{4},-4,\frac{3}{2}$ are chosen to illustrate. Observational properties involving dilepton signature at LHC, relativistic degrees of freedom $N_\text{eff}$, dark matter relic density, direct and indirect detections are comprehensively studied. Combined results of these observables for the benchmark scenarios imply that the resonance region $M_\text{DM}\sim M_{Z'}/2$ is the viable parameter space. Focusing on the resonance region, a scanning for TeV-scale dark matter is also performed to obtain current allowed and future prospective parameter space.

  • Pseudo-Dirac neutrinos from flavour dependent CP symmetry
    arXiv:1805.02002

    by: Joshipura, Anjan S.
    Abstract:
    Discrete residual symmetries and flavour dependent CP symmetries consistent with them have been used to constrain neutrino mixing angles and CP violating phases. We discuss here role of such CP symmetries in obtaining a pseudo-Dirac neutrino which can provide a pair of neutrinos responsible for the solar splitting. It is shown that if (a) $3\times 3$ Majorana neutrino matrix $M_\nu$ is invariant under a discrete $Z_2\times Z_2$ symmetry generated by $S_{1,2}$, (b) CP symmetry $X$ transform $M_\nu$ as $X^T M_\nu X=M_\nu^*$, and (c) $X$ and $S_{1,2}$ obey consistency conditions $X S_{1,2}^* X^\dagger=S_{2,1}$, then two of the neutrino masses are degenerate independent of specific forms of $X$, $S_1$ and $S_2$. Explicit examples of this result are discussed in the context of $\Delta(6 n^2)$ groups which can also be used to constrain neutrino mixing matrix $U$. Degeneracy in two of the masses does not allow complete determination of $U$ but it can also be fixed once the perturbations are introduced. We consider explicit perturbations which break $Z_2\times Z_2$ symmetries but respect CP. These are shown to remove the degeneracy and provide a predictive description of neutrino spectrum. In particular, a correlation $\sin 2\theta_{23}\sin\delta_{CP}=\pm {\rm Im}[p]$ is obtained between the atmospheric mixing angle $\theta_{23}$ and the CP violating phase $\delta_{CP}$ in terms of a group theoretically determined phase factor $p$. Experimentally interesting case $\theta_{23}=\frac{\pi}{4}$, $\delta_{CP}=\pm \frac{\pi}{2}$ emerges for groups which predict purely imaginary $p$. We present detailed predictions of the allowed ranges of neutrino mixing angles, phases and the lightest neutrino mass for three of the lowest $\Delta(6 n^2)$ groups with $n=2,4,6$.

  • Heavy physics contributions to neutrinoless double beta decay from QCD
    RIKEN-ITHEMS-REPORT-18
    arXiv:1805.02634

    by: Nicholson, A. (North Carolina U.) et al.

    Abstract:
    Observation of neutrinoless double beta decay, a lepton number violating process that has been proposed to clarify the nature of neutrino masses, has spawned an enormous world-wide experimental effort. Relating nuclear decay rates to high-energy, beyond the Standard Model (BSM) physics requires detailed knowledge of non-perturbative QCD effects. Using lattice QCD and taking advantage of effective field theory methods, we compute the model-independent leading-order matrix elements of short-range operators, which arise due to heavy BSM mediators, that contribute to this decay. Contributions from short-range operators may prove to be equally important to or even more important than those from long-range Majorana neutrino exchange.

  • Invisible neutrino decay in the light of NOvA and T2K data
    arXiv:1805.01848

    by: Choubey, Sandhya
    Abstract:
    We probe for evidence of invisible neutrino decay in the latest NOvA and T2K data. It is seen that both NOvA and T2K data sets are better fitted when one allows for invisible neutrino decay. We consider a scenario where only the third neutrino mass eigenstate $\nu_3$ is unstable and decays into invisible components. The best-fit value for the $\nu_3$ lifetime is obtained as $\tau_{3}/m_{3} = 3.16\times 10^{-12}$ s/eV from the analysis of the NOvA neutrino data and $\tau_{3}/m_{3} = 1.0\times 10^{-11}$ s/eV from the analysis of the T2K neutrino and anti-neutrino data. The combined analysis of NOvA and T2K gives $\tau_{3}/m_{3} = 5.01\times 10^{-12}$ s/eV as the best-fit lifetime. However, the statistical significance for this preference is weak with the no-decay hypothesis still allowed at close to 1.5$\sigma$ C.L. from the combined data sets, while the two experiment individually are consistent with no-decay even at the 1$\sigma$ C.L. At 3$\sigma$ C.L., the NOvA and T2K data give a lower limit on the neutrino lifetime of $\tau_{3}/m_{3}$ is $\tau_{3}/m_{3} \geq 7.22 \times 10^{-13}$ s/eV and $\tau_{3}/m_{3} \geq 1.41 \times 10^{-12}$ s/eV, respectively, while NOvA and T2K combined constrain $\tau_{3}/m_{3} \geq 1.50 \times 10^{-12}$ s/eV. We also show that in presence of decay the best-fit value in the $\sin^{2}\theta_{23}$ vs $\Delta m^{2}_{32}$ plane changes significantly and the allowed regions increase significantly towards higher $\sin^{2}\theta_{23}$.

  • Three-Loop Neutrino Masses via New Massive Gauge Bosons from E_6 GUT
    MI-TH-1882
    MI-TH-1882
    arXiv:1805.01866

    by: Dutta, Bhaskar (Texas A-M) et al.

    Abstract:
    We propose an SU(3)_C\times SU(2)_L \times SU(2)_N \times U(1)_Y model arising from E_6 Grand Unified Theory (GUT). We show that the tiny neutrino masses in this model can be generated at three-loop involving the SU(2)_N gauge bosons. With Yukawa couplings around 0.01 or larger and TeV-scale SU(2)_N gauge bosons, we show that the neutrino oscillation data can be explained naturally by presenting a concrete benchmark set of input parameters. All new particles are around the TeV scale. Thus our model can be tested at the ongoing/future collider experiments.

  • On the systematic uncertainties in DUNE and their role in New Physics studies
    arXiv:1805.01747

    by: Meloni, Davide (Rome III U.)

    Abstract:
    In the recent years experiments have established the existence of neutrino oscillations and most of the oscillation parameters have been measured with a good accuracy. The search for New Physics in neutrino oscillation will be an experimental concrete possibility in the next future. In this paper we investigate the ability of the DUNE facility to search for Non Standard Interaction (NSI) in neutrino propagation in matter, emphasizing the role of different assumptions on the shape and absolute normalization errors of both $\nu_e$ and $\nu_\mu$ signals. We also study in detail the effects of NSI and systematics in the extraction of standard oscillation parameters.

  • Prospects for exploring New Physics in Coherent Elastic Neutrino-Nucleus Scattering
    arXiv:1805.01798

    by: Billard, Julien (Lyon, IPN) et al.

    Abstract:
    Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) is a Standard Model process that, although predicted for decades, has only been detected recently by the COHERENT collaboration. Now that CE$\nu$NS has been discovered, it provides a new probe for physics beyond the Standard Model. We study the potential to probe New Physics with CE$\nu$NS through the use of low temperature bolometers at a reactor source. We consider contributions to CE$\nu$NS due to a neutrino magnetic moment (NMM), Non-Standard Interactions (NSI) that may or may not change flavor, and simplified models containing a massive scalar or vector mediator. Targets consisting of Ge, Zn, Si, CaWO$_4$, and Al$_2$O$_3$ are examined. We show that by reaching a percentage-level precision measurement on the CE$\nu$NS energy spectrum down to $\mathcal{O}(10)$ eV, forthcoming experiments will improve by two orders of magnitude both the CE$\nu$NS-based NMM limit and the search for new massive mediators. Additionally, we demonstrate that such dedicated low-threshold CE$\nu$NS experiments will lead to unprecedented constraints on NSI parameters (particularly when multiple targets are combined) which will have major implications for the global neutrino physics program.

  • Inverse seesaw and dark matter in a gauged B-L extension with flavour symmetry
    arXiv:1805.00568

    by: Biswas, Anirban (Indian Inst. Tech., Guwahati) et al.

    Abstract:
    We propose a model which generates neutrino masses by the inverse seesaw mechanism, provides a viable dark matter candidate and explains the muon ($g-2$) anomaly. The Standard Model (SM) gauge group is extended with a gauged U(1)$_{\rm B-L}$ as well as a gauged U(1)$_{\rm L_{\mu} - L_{\tau}}$. While U(1)$_{\rm L_{\mu} - L_{\tau}}$ is anomaly free, the anomaly introduced by U(1)$_{\rm B-L}$ is cancelled between the six SM singlet fermions introduced for the inverse seesaw mechanism and four additional chiral fermions introduced in this model. After spontaneous symmetry breaking the four chiral fermionic degrees of freedom combine to give two Dirac states. The lightest Dirac fermion becomes stable and hence the dark matter candidate. We focus on the region of the parameter space where the dark matter annihilates to the right-handed neutrinos, relating the dark matter sector with the neutrino sector. The U(1)$_{\rm L_{\mu} - L_{\tau}}$ gauge symmetry provides a flavour structure to the inverse seesaw framework, successfully explaining the observed neutrino masses and mixings. We study the model parameters in the light of neutrino oscillation data and find correlation between them. Values of some of the model parameters are shown to be mutually exclusive between normal and inverted ordering of the neutrino mass eigenstates. Moreover, the muon ($g-2$) anomaly can be explained by the additional contribution arising from U(1)$_{\rm L_{\mu} - L_{\tau}}$ gauge boson.

  • On the Properties of Neutrinos
    arXiv:1805.00922

    by: Baha Balantekin, A. (Wisconsin U., Madison) et al.

    Abstract:
    Our present understanding of neutrino properties is reviewed with a particular emphasis on observable differences between Majorana and Dirac neutrinos. Current and future experimental efforts towards measuring neutrino properties are summarized. Consequences of the Majorana vs.Dirac nature of neutrinos on neutrino masses, neutrino decays, and neutrino electromagnetic properties are described.

  • Nucleon axial form factor from a Bayesian neural-network analysis of neutrino-scattering data
    arXiv:1805.00905

    by: Alvarez-Ruso, Luis (Valencia U., IFIC) et al.

    Abstract:
    The Bayesian approach for feed-forward neural networks has been applied to the extraction of the nucleon axial form factor from the neutrino-deuteron scattering data measured by the Argonne National Laboratory (ANL) bubble chamber experiment. This framework allows to perform a model-independent determination of the axial form factor from data.. When the low $0.05 < Q^2 < 0.10$ GeV$^2$ data is included in the analysis, the resulting axial radius disagrees with available determinations. Furthermore, a large sensitivity to the corrections from the deuteron structure is obtained. In turn, when the low-$Q^2$ region is not taken into account, with or without deuteron corrections, no significant deviations from the dipole ansatz have been observed. A more accurate determination of the nucleon axial form factor requires new precise measurements of neutrino-induced quasielastic scattering on hydrogen and deuterium.

  • On anisotropy of the maximum attainable speed of low-mass particles
    arXiv:1805.00408

    by: Wojtsekhowski, B. (Jefferson Lab)

    Abstract:
    We show that for a non-zero photon mass, $m_{ph}$, the speed of light anisotropy, $\delta c/c$, is below $10^{-37}$ based on an accepted bound on $m_{ph}$. A strong bound was also obtained in the case of the neutrino.

  • Natural Higgs Inflation, Gauge Coupling Unification, and Neutrino Masses
    arXiv:1805.00161

    by: Chen, Heng-Yu (Delaware U.) et al.

    Abstract:
    We present two non-supersymmetric models involving different content of additional vector-like fermions. In both models, gauge coupling unification, neutrino mass generation and Higgs inflation mechanism are related to each other. It is known that when TeV scale vector-like fermions are introduced in order to implement the Standard Model (SM) gauge coupling unification, it also solves the SM Higgs vacuum stability problem. Involving additional new state at intermediate scale makes it possible to give successful gauge coupling unification even at reduced Planck scale. We adopt in our models Type I seesaw mechanism for neutrino masses. Appropriate choice of the type I Seesaw scale allows us to have an arbitrarily small but positive value of SM Higgs quartic coupling around the reduced Planck scale. Implementing this observation into the SM Higgs inflation models leads us to have the non-minimal coupling $\xi$ between Higgs field and Ricci scalar less then 100. We present a few benchmark points where we show that the scalar spectral indices are around 0.9626 and 0.9685 respectively for the number of e-folding $N=50$ and $N=60$. The tensor-to-scalar ratios are at the order of $10^{-3}$. The running of the scalar spectral index is negative and is order of $10^{-4}$.

  • Probing heavy neutrino oscillations in rare W boson decays
    arXiv:1805.00070

    by: Cvetič, Gorazd (Santa Maria U., Valparaiso) et al.

    Abstract:
    In this work, we study the lepton number violating W boson and top quark decays via intermediate on-shell Majorana neutrinos Nj into three charged leptons and a light neutrino. We discuss the neutrino oscillation effects present in the decay due to the small mass gap between the heavy neutrino states. We focus on a scenario that contains at least two heavy Majorana neutrinos in the mass range 2-80 GeV. The results show that CP-phases could be observed in a future experiment such as High-Luminosity Large Hadron Collider. We also present regions of the heavy-light neutrino mixing in which the abovementioned phases could be explored.

  • Constraining Non-Cold Dark Matter Models with the Global 21-cm Signal
    arXiv:1805.00021

    by: Schneider, Aurel (ETH, Zurich (main))

    Abstract:
    Any particle dark matter (DM) scenario featuring a suppressed power spectrum of astrophysical relevance results in a delay of galaxy formation. As a consequence, such scenarios can be constrained using the global 21-cm absorption signal initiated by the UV radiation of the first stars. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported the first detection of such an absorption signal at redshift $\sim 17$. While its amplitude might indicate the need for new physics, we solely focus on the timing of the signal to test non-cold DM models. Assuming a conservative upper limit for star-formation based on radiation-hydrodynamics simulations, we are able to derive unprecedented constraints on a variety of non-cold DM models. For example, the mass of thermal warm DM is limited to $m_{\rm TH}>6.1$ keV, while mixed DM scenarios (featuring a cold and a hot component) are constrained to a hot DM fraction below 17 percent. The ultra-light axion DM model is limited to masses $m_{a}>8\times10^{-21}$ eV, a regime where its wave-like nature is pushed far below the kiloparsec scale. Finally, sterile neutrinos from resonant production can be fully disfavoured as a dominant DM candidate. The results of this paper show that the 21-cm absorption signal is a powerful discriminant of non-cold dark matter, allowing for significant improvements over to the strongest current limits. Confirming the result from EDGES is paramount in this context.

  • Optimizing the $^{8}$Li yield for the IsoDAR Neutrino Experiment
    arXiv:1805.00410

    by: Bungau, Adriana (MIT) et al.

    Abstract:
    The focus of this paper is on optimizing the electron-antineutrino source for the IsoDAR (Isotope Decay at Rest) experimental program. IsoDAR will perform sensitive short-baseline neutrino oscillation and electroweak measurements, among other Beyond Standard Model searches, in combination with KamLAND and/or other suitable detectors. IsoDAR will rely on the high-$Q$ $\beta^-$ decay of the $^{8}$Li isotope for producing electron-antineutrinos, created mainly via neutron capture in an isotopically enriched $^{7}$Li sleeve surrounding the Be target. In particular, this paper examines the performance, defined in terms of absolute $^{8}$Li (or, equivalently, electron-antineutrino) production rate, of various candidate sleeve materials, including a lithium-fluoride, beryllium-fluoride mixture ("FLiBe") sleeve and a homogeneous mixture of lithium and beryllium ("Li-Be"). These studies show that the $^{8}$Li yield can be increased substantially by employing a Li-Be sleeve and therefore motivate significant changes to the nominal IsoDAR design.

  • Novel neutrino-floor and dark matter searches with deformed shell model calculations
    arXiv:1804.11319

    by: Papoulias, D.K. (Democritos Nucl. Res. Ctr.) et al.

    Abstract:
    Event detection rates for WIMP-nucleus interactions are calculated for $^{71}$Ga, $^{73}$Ge, $^{75}$As and $^{127}$I (direct dark matter detectors). The nuclear structure form factors, that are rather independent of the underlying beyond the Standard Model particle physics scenario assumed, are evaluated within the context of the deformed nuclear shell model (DSM) based on Hartree-Fock nuclear states. Along with the previously published DSM results for $^{73}$Ge, the neutrino-floor due to coherent elastic neutrino-nucleus scattering (CE$\nu$NS), an important source of background to dark matter searches, is extensively calculated. The impact of new contributions to CE$\nu$NS due to neutrino magnetic moments and $Z^\prime$ mediators at direct dark matter detection experiments is also examined and discussed. The results show that the neutrino-floor constitutes a crucial source of background events for multi-ton scale detectors with sub-keV capabilities.

  • Neutrino mixing and General Covariance in the inverse beta decay
    arXiv:1804.11211

    by: Blasone, M. (Salerno U.) et al.

    Abstract:
    We review recent developments on the role of neutrino mixing in the inverse beta decay of accelerated protons. We show that calculations in the inertial and comoving frames agree (thus preserving General Covariance) only when taking neutrino asymptotic states to be flavor (rather than mass) eigenstates. Our conclusions are valid in the approximation in which Pontecorvo states are correctly representing neutrino flavor states. We speculate about the general case involving exact flavor states and finally comment on other approaches recently appeared in literature.

  • Revised constraints on hidden photons produced in nuclear reactors
    INR-TH-2018-009
    INR-TH-2018-009
    arXiv:1804.10777

    by: Danilov, Mikhail (Lebedev Inst.) et al.

    Abstract:
    New light vector particles - hidden photons - are present in many extensions of the Standard Model of particle physics. They can be produced in nuclear reactors and registered by neutrino detectors. New limits on the models with hidden photons have been obtained in arXiv:1705.02470v4 [hep-ph] from analysis of published results of the NEOS and TEXONO neutrino experiments. We criticize that paper from both theoretical and experimental points of view. Accounting for oscillations between visible and hidden photons, we find that the neutrino experiments are generally insensitive to the hidden photons lighter than $\sim 0.1$\,eV, and present revised limits for heavier hidden photons from results of the TEXONO experiment.

  • Revisiting $A_4$ model for leptons in light of NuFIT 3.2
    HUPD1801
    HUPD1801
    arXiv:1804.10468

    by: Kang, Sin Kyu (Seoul Natl. U.) et al.

    Abstract:
    We revisit the $A_4$ model for leptons in light of new result of NuFIT 3.2. We introduce a new flavon $\eta$ transforming as $A_4$ singlet $1'$ or $1"$ which couples to both charged leptons and neutrinos in next-leading order operators. The model consists of the five parameters: the lightest neutrino mass $m_1$, the vacuum expectation value of $\eta$ and three CP violating phases after inputting the experimental values of $\Delta m_{\rm atm}^2$ and $\Delta m_{\rm sol}^2$. The model with the $1"$ singlet flavon gives the prediction of $\sin^2 \theta_{12}$ around the best fit of NuFIT 3.2 while keeping near the maximal mixing of $\theta_{23}$. Inputting the experimental mixing angles with the $1\,\sigma$ error-bar, the Dirac CP violating phase is clearly predicted to be $|\delta_\text{CP}|=50^\circ- 120^\circ$, which will be tested by the precise observed value in the future. In order to get the best fit value $\sin^2\theta_{23}=0.538$, the sum of three neutrino masses is predicted to be larger than $90\,$meV. The cosmological observation for the sum of neutrino masses will also provide a crucial test of our predictions. It is remarked that the model is consistent with the experimental data only for the normal hierarchy of neutrino masses.

  • Photons coming from an opaque obstacle as a manifestation of heavy neutrino decays
    arXiv:1804.10065
    Phys.Rev. D97 (2018) 095021

    by: Reynoso, Matías M. (IFIMAR, Buenos Aires) et al.

    Abstract:
    Within the framework of physics beyond the standard model we study the possibility that mesons produced in the atmosphere by the cosmic ray flux, decay to heavy Majorana neutrino and these mostly to photons in the low mass region. We study the photon flux produced by sterile Majorana neutrinos ($N$) decaying after passing through a massive and opaque object such as a mountain. In order to model the production of $N$'s in the atmosphere and their decay to photons, we consider the interaction between the Majorana neutrinos and the standard matter as modeled by an effective theory. We then calculate the heavy neutrino flux originated by the decay of mesons in the atmosphere. The surviving photon flux, originated by $N$ decays, is calculated using transport equations that include the effects of Majorana neutrino production and decay.

  • Type II Seesaw with scalar dark matter in light of AMS-02, DAMPE and Fermi-LAT
    arXiv:1804.09835

    by: Li, Tong (Monash U.) et al.

    Abstract:
    The Standard Model (SM) supplemented by Type II Seesaw and a SM gauge-singlet scalar dark matter (DM) is a very simple framework to incorporate the observed neutrino oscillations and provide a plausible DM candidate. In this framework, the scalar DM naturally has a leptophilic nature with a pair annihilating mainly into the SM SU(2)$_L$ triplet Higgs scalar of Type II Seesaw which, in turn, decay into leptons. In this work, we consider indirect signatures of this leptophilic DM and examine the spectrum of the cosmic ray electron/positron flux from DM pair annihilations in the Galactic halo. Given an astrophysical background spectrum of the cosmic ray electron/positron flux, we find that the contributions from DM annihilations can nicely fit the observed data from the AMS-02, DAMPE and Fermi-LAT collaborations, with a multi-TeV range of DM mass and a boost factor for the DM annihilation cross section of ${\cal O}(1000)$. The boost factor has a slight tension with the Fermi-LAT data for gamma-ray from dwarf spheroidal galaxies, which can be ameliorated with an enhanced local DM density by a factor of about 2.

  • Dimension-six electroweak top-loop effects in Higgs production and decay
    arXiv:1804.09766

    by: Vryonidou, Eleni (CERN) et al.

    Abstract:
    We study the next-to-leading order electroweak corrections to Higgs processes from dimension-six top-quark operators in the Standard Model Effective Field Theory approach. We consider the major production channels, including $WH$, $ZH$, and VBF production at the LHC, and $ZH$, VBF production at future lepton colliders, as well as the major decay channels including $H\to \gamma\gamma, \gamma Z, Wl\nu,Zll,b\bar b,\mu\mu,\tau\tau$. The results show that within the current constraints, top-quark operators can shift the signal strength of the loop-induced processes, i.e. $H\to \gamma\gamma,\gamma Z$, by factors of $\sim\mathcal{O}(1)-\mathcal{O}(10)$, and that of the tree-level processes, i.e. all remaining production and decay channels, by $\sim5-10\%$ at the LHC, and up to $\sim15\%$ at future lepton colliders. This implies that essentially all Higgs channels have started to become sensitive to top-quark couplings, and in particular, Higgs observables at high luminosity LHC as well as future lepton colliders, even below the $t\bar t$ threshold, will improve our knowledge of top-quark couplings. We derive the sensitivities of Higgs measurements to top-quark operators at the high luminosity LHC, using projections for both inclusive and differential measurements. We conclude that treating the dimension-six top-quark sector and the Higgs/electroweak sector separately may not continue to be a good strategy. A global analysis combining Higgs and top-quark measurements is desirable, and our calculation and implementation provide an automatic and realistic simulation tool for this purpose.

  • Surface tension of quark droplets in compact stars and in the early universe
    arXiv:1804.09898

    by: Grunfeld, A.G. (Buenos Aires, CONICET) et al.

    Abstract:
    We review the role of the surface tension of quark matter droplets in astrophysical conditions, focusing specifically on the thermodynamic conditions prevailing in cold neutron stars (NSs), in hot lepton rich proto NSs, and in early universe conditions. We analyze quark matter in chemical equilibrium under weak interactions, which is relevant for understanding the internal composition of hybrid stars, as well as just deconfined quark matter out of chemical equilibrium, which is the relevant thermodynamic state for describing the nucleation process of quark matter in NSs. We explore the role of temperature, density, trapped neutrinos, droplet size and magnetic fields within the multiple reflection expansion formalism (MRE). Quark matter is described within the frame of different effective models: the MIT bag model and the $SU(3)_f$ Nambu-Jona-Lasinio model (NJL), including color superconductivity, neutrino trapping and magnetic fields. We also analyze the deconfinement transition at vanishing chemical potential and finite temperature including the Polyakov loop. We explore some astrophysical consequences of our results.

  • Natural and Dynamical Neutrino Mass Mechanism at the LHC
    arXiv:1804.09184
    FERMILAB-PUB-18-127-T

    by: Gehrlein, Julia (Madrid, Autonoma U.) et al.

    Abstract:
    We generalize the scalar triplet neutrino mass model, the type II seesaw. Requiring fine-tuning and arbitrarily small parameters to be absent leads to dynamical lepton number breaking at the electroweak scale and a rich LHC phenomenology. A smoking gun signature at the LHC that allows to distinguish our model from the usual type II seesaw scenario is identified. Besides, we discuss other interesting phenomenological aspects of the model such as the presence of a massless Goldstone boson and deviations of standard model Higgs couplings

  • Low-Scale Leptogenesis in the Scotogenic Neutrino Mass Model
    arXiv:1804.09660

    by: Hugle, Thomas (Heidelberg, Max Planck Inst.) et al.

    Abstract:
    The scotogenic model proposed by Ernest Ma represents an attractive and minimal example for the generation of small Standard Model neutrino masses via radiative corrections in the dark matter sector. In this paper, we demonstrate that, in addition to neutrino masses and dark matter, the scotogenic model also allows to explain the baryon asymmetry of the Universe via low-scale leptogenesis. First, we consider the case of two right-handed neutrinos (RHNs) N_{1,2}, for which we provide an analytical argument why it is impossible to push the RHN mass scale below M_1^min ~ 10^10 GeV, which is identical to the value in standard thermal leptogenesis in the type-I seesaw scenario with the same washout strength. Then, we present a detailed study of the three-RHN case based on both an analytical and a numerical analysis. In the case of three RHNs, we obtain a lower bound on the N_1 mass of around 10 TeV. Remarkably enough, successful low-scale leptogenesis can be achieved without any degeneracy in the RHN mass spectrum. The only necessary condition is a suppression in the N_1 Yukawa couplings, which results in suppressed washout and a small active neutrino mass of around 10^-12 eV. This leads to the fascinating realization that low-scale leptogenesis in the scotogenic model can be tested in experiments that aim at measuring the absolute neutrino mass scale.

  • Active-sterile neutrino oscillations at INO-ICAL over a wide mass-squared range
    IP/BBSR/2018-2
    TIFR/TH/18-07
    IP-BBSR-2018-2
    TIFR-TH-18-07
    arXiv:1804.09613

    by: Thakore, Tarak (Louisiana State U.) et al.

    Abstract:
    We perform for the first time a detailed search for active-sterile oscillations involving a light sterile neutrino, over a large $\Delta m^2_{41}$ range of $10^{-5}$ eV$^2$ to $10^2$ eV$^2$, using 10 years of atmospheric neutrino data expected from the proposed 50 kt magnetized ICAL detector at the INO. This detector can observe the atmospheric $\nu_{\mu}$ and $\bar\nu_{\mu}$ separately over a wide range of energies and baselines, making it sensitive to the magnitude and sign of $\Delta m^2_{41}$ over a large range. If there is no light sterile neutrino, ICAL can place competitive upper limit on $|U_{\mu 4}|^2 \lesssim 0.02$ at 90\% C.L. for $\Delta m^2_{41}$ in the range $(0.5 - 5) \times 10^{-3}$ eV$^2$. For the same $|\Delta m^2_{41}|$ range, ICAL would be able to determine its sign, exploiting the Earth's matter effect in $\mu^{-}$ and $\mu^{+}$ events separately if there is indeed a light sterile neutrino in Nature. This would help identify the neutrino mass ordering in the four-neutrino mixing scenario.

  • Sensitivity of Neutrino-Nucleus Interaction Measurements to 2p2h Excitations
    arXiv:1804.09488

    by: Dolan, Stephen (Ecole Polytechnique) et al.

    Abstract:
    We calculate the charged-current cross sections obtained at the T2K off-axis near detector for $\nu_\mu$-induced events without pions and any number of protons in the final state using transport theory as encoded in the GiBUU model. In a comparison with recent T2K data the strength of the 2p2h multinucleon correlations is determined. Linking this to the isospin (T) of the initial nuclear state, it is found that T=0 leads to a significantly better fit of the recent cross sections obtained by T2K, thus achieving consistency of the 2p2h multi-nucleon correlation contributions between electron-nucleus and neutrino-nucleus reactions.

  • Current unknowns in the three neutrino framework
    arXiv:1804.09678

    by: Capozzi, F. (Munich, Max Planck Inst.) et al.

    Abstract:
    We present an up-to-date global analysis of data coming from neutrino oscillation and non-oscillation experiments, as available in April 2018, within the standard framework including three massive and mixed neutrinos. We discuss in detail the status of the three-neutrino (3nu) mass-mixing parameters, both known and unknown. Concerning the latter, we find that: normal ordering (NO) is favored over inverted ordering (IO) at 3sigma level; the Dirac CP phase is constrained within ~15% (~9%) uncertainty in NO (IO) around nearly-maximal CP-violating values; the octant of the largest mixing angle and the absolute neutrino masses remain undetermined. We briefly comment on other unknowns related to theoretical and experimental uncertainties (within 3nu) or possible new states and interactions (beyond 3nu).

  • B-L Model with ${\bf S}_{3}$ Symmetry: Nearest Neighbor Interaction Textures and Broken $\mu\leftrightarrow\tau$ Symmetry
    arXiv:1804.08746

    by: Gómez-Izquierdo, Juan Carlos (Mexico U.) et al.

    Abstract:
    We make a scalar extension of the B-L gauge model where the ${\bf S}_{3}$ non-abelian discrete group drives mainly the Yukawa sector. Motived by the large and small hierarchies among the quark and active neutrino masses respectively, the quark and lepton families are not treated on the same footing under the assignment of the discrete group. As a consequence, the Nearest Neighbor Interactions (NNI) textures appear in the quark sector, leading to the CKM mixing matrix, whereas in the lepton sector, a soft breaking of the $\mu \leftrightarrow \tau$ symmetry in the effective neutrino mass that comes from type I see-saw mechanism, provides a non-maximal atmospheric angle and a non-zero reactor angle.

  • Neutral-current neutrino-nucleus scattering off Xe isotopes
    arXiv:1804.08995

    by: Pirinen, P. (Jyvaskyla U.) et al.

    Abstract:
    Large liquid xenon detectors aiming for dark matter direct detection will soon become viable tools also for investigating neutrino physics. Information on the effects of nuclear structure in neutrino-nucleus scattering can be important in distinguishing neutrino backgrounds in such detectors. We perform calculations for differential and total cross sections of neutral-current neutrino scattering off the most abundant xenon isotopes. The nuclear structure calculations are made in the nuclear shell model for elastic scattering, and also in the quasiparticle random-phase approximation (QRPA) and microscopic quasiparticle phonon model (MQPM) for both elastic and inelastic scattering. Using suitable neutrino energy distributions, we compute estimates of total averaged cross sections for 8B solar neutrinos and supernova neutrinos.

  • The spectroscopy of solar sterile neutrinos
    arXiv:1804.08344
    Eur.Phys.J. C78 (2018) 327

    by: Lopes, Ilídio (Lisbon, CENTRA)

    Abstract:
    We predict the sterile neutrino spectrum of some of the key solar nuclear reactions and discuss the possibility of these being observed by the next generation of solar neutrino experiments. By using an up-to-date standard solar model with good agreement with current helioseismology and solar neutrino flux data sets, we found that from solar neutrino fluxes arriving on Earth only 3\%-4\% correspond to the sterile neutrino. The most intense solar sources of sterile neutrinos are the $pp$ and $^7Be$ nuclear reactions with a total flux of $2.2\times 10^{9}\;{\rm cm^2 s^{-1}}$ and $1.8\times 10^{8}\;{\rm cm^2 s^{-1}}$, followed by the $^{13}N$ and $^{15}O$ nuclear reactions with a total flux of $1.9\times 10^{7}\;{\rm cm^2 s^{-1}}$ and $1.7\times 10^{7}\;{\rm cm^2 s^{-1}}$. Moreover, we compute the sterile neutrino spectra of the nuclear proton-proton nuclear reactions -- $pp$, $hep$ and $^8B$ and the carbon-nitrogen-oxygen -- $^{13}N$, $^{15}O$ and $^{17}F$ and the spectral lines of $^7Be$.

  • Detection techniques and investigation of different neutrino experiments
    arXiv:1804.08467

    by: Nath, Ankur (Tezpur U.) et al.

    Abstract:
    Neutrino physics is an experimentally driven field. So, we investigate the different detection techniques available in the literature and study the various neutrino oscillation experiments in a chronological manner. Our primary focus is on the construction and detection mechanisms of each experiment. Today, we know a lot about this mysterious ghostly particle by performing different experiments at different times with different neutrino sources viz. solar, atmospheric, reactor, accelerators and high energy astrophysical; and they have contributed in the determination of neutrino parameters. Yet the problems are far from over. We need to determine more precise values of the already known parameters and unravel the completely unknown parameters. Some of the unknowns are absolute masses of neutrino, types of neutrino, mass hierarchy, octant degeneracy and existence of leptonic CP Phase(s). We analyse the neutrino experiments into the past, present and the future (or proposed). We include SNO, Kamiokande, K2K, MINOS, Chooz and NEMO in the past; while Borexino, Double Chooz, Super-K, T2K, IceCube, KamLAND, MINOS+, NO$\nu$A, RENO and Daya Bay in the present; and SNO+, Hyper-K, JUNO, RENO-50, INO, DUNE and SuperNEMO in the proposed experiments. We also discuss the necessities of upgrading the present ones to those of the proposed ones thereby summarizing the potentials of the future experiments. We conclude this paper with the current status of the neutrinos.

  • The Standard Model and Higgs physics
    Prog.Part.Nucl.Phys. 100 (2018) 69-106

    by: Torassa, Ezio (INFN, Padua)

    Abstract:
    The Standard Model is a consistent and computable theory that successfully describes the elementary particle interactions. The strong, electromagnetic and weak interactions have been included in the theory exploiting the relation between group symmetries and group generators, in order to smartly introduce the force carriers. The group properties lead to constraints between boson masses and couplings. All the measurements performed at the LEP, Tevatron, LHC and other accelerators proved the consistency of the Standard Model. A key element of the theory is the Higgs field, which together with the spontaneous symmetry breaking, gives mass to the vector bosons and to the fermions. Unlike the case of vector bosons, the theory does not provide prediction for the Higgs boson mass. The LEP experiments, while providing very precise measurements of the Standard Model theory, searched for the evidence of the Higgs boson until the year 2000. The discovery of the top quark in 1994 by the Tevatron experiments and of the Higgs boson in 2012 by the LHC experiments were considered as the completion of the fundamental particles list of the Standard Model theory. Nevertheless the neutrino oscillations, the dark matter and the baryon asymmetry in the Universe evidence that we need a new extended model. In the Standard Model there are also some unattractive theoretical aspects like the divergent loop corrections to the Higgs boson mass and the very small Yukawa couplings needed to describe the neutrino masses. For all these reasons, the hunt of discrepancies between Standard Model and data is still going on with the aim to finally describe the new extended theory.

  • Propagation of GeV neutrinos through Earth
    JHEAp 18 (2018) 35-42

    by: Olivas, Yaithd Daniel (Mexico U., ICN) et al.

    Abstract:
    We have studied the Earth matter effect on the oscillation of upward going GeV neutrinos by taking into account the three active neutrino flavors. For neutrino energy in the range 3 to 12 GeV we observed three distinct resonant peaks for the oscillation process νe↔νμ,τ in three distinct densities. However, according to the most realistic density profile of the Earth, the second peak at neutrino energy 6.18 GeV corresponding to the density 6.6 g/cm 3 does not exist. So the resonance at this energy can not be of MSW-type. For the calculation of observed flux of these GeV neutrinos on Earth, we considered two different flux ratios at the source, the standard scenario with the flux ratio 1:2:0 and the muon damped scenario with 0:1:0 . It is observed that at the detector while the standard scenario gives the observed flux ratio 1:1:1 , the muon damped scenario has a different ratio. For muon damped case with Eν<20 GeV, we always get observed neutrino fluxes as Φνe<Φνμ≃Φντ and for Eν>20 GeV, we get the average Φνe∼0 and Φνμ≃Φντ≃0.45 . The upcoming PINGU will be able to shed more light on the nature of the resonance in these GeV neutrinos and hopefully will also be able to discriminate among different processes of neutrino production at the source in GeV energy range.

  • Texture One Zero Dirac Neutrino Mass Matrix With Vanishing Determinant or Trace Condition
    arXiv:1804.00842
    Nucl.Phys. B931 (2018) 446-468

    by: Singh, Madan (Kurukshetra U.)

    Abstract:
    In the light of non-zero and relatively large value of rector mixing angle ($\theta_{13}$), we have performed a detailed analysis of texture one zero neutrino mass matrix $M_{\nu}$ in the scenario of vanishing determinant/trace conditions , assuming the Dirac nature of neutrinos. In both the scenarios, normal mass ordering is ruled out for all the six possibilities of $M_{\nu}$, however for inverted mass ordering, only two are found to be viable with the current neutrino oscillation data at $3\sigma$ confidence level. Numerical and some approximate analytical results are presented.

  • Zooming in on neutrino oscillations with DUNE
    IFIC/18-xxx
    arXiv:1803.10247
    IFIC-18-XXX
    Phys.Rev. D97 (2018) 095025

    by: Srivastava, Rahul (Valencia U., IFIC) et al.

    Abstract:
    We examine the capabilities of the DUNE experiment as a probe of the neutrino mixing paradigm. Taking the current status of neutrino oscillations and the design specifications of DUNE, we determine the experiment's potential to probe the structure of neutrino mixing and CP violation. We focus on the poorly determined parameters $\theta_{23}$ and $\delta_{CP}$ and consider both two and seven years of run. We take various benchmarks as our true values, such as the current preferred values of $\theta_{23}$ and $\delta_{CP}$, as well as several theory-motivated choices. We determine quantitatively DUNE's potential to perform a precision measurement of $\theta_{23}$, as well as to test the CP violation hypothesis in a model-independent way. We find that, after running for seven years, DUNE will make a substantial step in the precise determination of these parameters, bringing to quantitative test the predictions of various theories of neutrino mixing.

  • The $0\nu\beta\beta$-decay nuclear matrix element for light and heavy neutrino mass mechanisms from deformed QRPA cacluations for $^{76}$Ge, $^{82}$Se, $^{130}$Te, $^{136}$Xe and $^{150}$Nd with isospin restoration
    arXiv:1803.09195
    Phys.Rev. C97 (2018) 045503

    by: Fang, Dong-Liang (Jilin U.) et al.

    Abstract:
    In this paper, with restored isospin symmetry, we evaluated the neutrinoless double-β-decay nuclear matrix elements for Ge76, Se82, Te130, Xe136, and Nd150 for both the light and heavy neutrino mass mechanisms using the deformed quasiparticle random-phase approximation approach with realistic forces. We give detailed decompositions of the nuclear matrix elements over different intermediate states and nucleon pairs, and discuss how these decompositions are affected by the model space truncations. Compared to the spherical calculations, our results show reductions from 30% to about 60% of the nuclear matrix elements for the calculated isotopes mainly due to the presence of the BCS overlap factor between the initial and final ground states. The comparison between different nucleon-nucleon (NN) forces with corresponding short-range correlations shows that the choice of the NN force gives roughly 20% deviations for the light exchange neutrino mechanism and much larger deviations for the heavy neutrino exchange mechanism.

  • Role of neutrino mixing in accelerated proton decay
    arXiv:1803.05695
    Phys.Rev. D97 (2018) 105008

    by: Blasone, Massimo (Salerno U.) et al.

    Abstract:
    The inverse beta decay of accelerated protons has been analyzed both in the laboratory frame (where the proton is accelerated) and in the comoving frame (where the proton is at rest and interacts with the Fulling-Davies-Unruh thermal bath of electrons and neutrinos). The equality between the two rates has been exhibited as an evidence of the necessity of Fulling-Davies-Unruh effect for the consistency of Quantum Field Theory formalism. Recently, it has been argued that neutrino mixing can spoil such a result, potentially opening new scenarios in neutrino physics. In the present paper, we analyze in detail this problem and we find that, assuming flavor neutrinos to be fundamental and working within a certain approximation, the agreement can be restored.

  • Liouville term for neutrinos: Flavor structure and wave interpretation
    MPP-2018-14
    MPP-2018-14
    arXiv:1803.04693
    JCAP 1805 (2018) 016

    by: Stirner, Tobias (Munich, Max Planck Inst.) et al.

    Abstract:
    Neutrino production, absorption, transport, and flavor evolution in astrophysical environments is described by a kinetic equation D=−i[H,]+[]. Its basic elements are generalized occupation numbers , matrices in flavor space, that depend on time t, space x, and momentum p. The commutator expression encodes flavor conversion in terms of a matrix H of oscillation frequencies, whereas [] represents source and sink terms as well as collisions. The Liouville operator on the left hand side involves linear derivatives in t, x and p. The simplified expression D=∂t+⋅∂x for ultra-relativistic neutrinos was recently questioned in that flavor-dependent velocities should appear instead of the unit vector . Moreover, a new damping term was postulated as a result. We here derive the full flavor-dependent velocity structure of the Liouville term although it appears to cause only higher-order corrections. Moreover, we argue that on the scale of the neutrino oscillation length, the kinetic equation can be seen as a first-order wave equation.

  • Zee-Babu type model with $U(1)_{L_\mu - L_\tau}$ gauge symmetry
    KIAS-P18024
    KIAS-P18024
    arXiv:1803.04795
    Phys.Rev. D97 (2018) 095023

    by: Nomura, Takaaki (Korea Inst. Advanced Study, Seoul) et al.

    Abstract:
    We extend the Zee-Babu model introducing local $U(1)_{L_\mu - L_\tau}$ symmetry with several singly-charged bosons. We find a predictive neutrino mass texture in a simple hypothesis that mixings among singly-charged bosons are negligible. Also lepton flavor violations are less constrained compared with the original model. Then we explore testability of the model focussing on a doubly-charged boson physics at the LHC and the ILC.

  • Connecting Majorana phases to the Geometric Parameters of Majorana Unitarity Triangle in a model of Neutrino Mass Matrix
    arXiv:1803.04162
    Phys.Rev. D97 (2018) 095022

    by: Verma, Surender (Himachal Pradesh U.) et al.

    Abstract:
    We have investigated a possible connection between the Majorana phases and geometric parameters of leptonic unitarity triangle(LUT) in two-texture zero neutrino mass matrix. Such analytical relations can, also, be obtained for other theoretical models viz. hybrid textures, neutrino mass matrix with vanishing minors and have profound implications for geometric description of $CP$ violation. As an example, we have considered two-texture zero neutrino mass model to obtain relation between Majorana phases and LUT parameters. In particular, we find that Majorana phases depend on only one of the three interior angles of LUT in each class of two-texture zero neutrino mass matrix. We have, also, constructed LUT for class $A$, $B$ and $C$ neutrino mass matrices. Non-vanishing areas and nontrivial orientations of these Majorana unitarity triangles indicate non-zero $CP$ violation as a generic feature of this class of mass models.

  • Matter effects on the flavor conversions of solar neutrinos and high-energy astrophysical neutrinos
    arXiv:1803.02037
    Nucl.Phys. B931 (2018) 324-341

    by: Huang, Guo-yuan (Beijing, Inst. High Energy Phys.) et al.

    Abstract:
    Can we observe the solar eclipses in the neutrino light? In principle, this is possible by identifying the lunar matter effects on the flavor conversions of solar neutrinos when they traverse the Moon before reaching the detectors at the Earth. Unfortunately, we show that the lunar matter effects on the survival probability of solar $^8{\rm B}$ neutrinos are suppressed by an additional factor of $1.2\%$, compared to the day-night asymmetry. However, we point out that the matter effects on the flavor conversions of high-energy astrophysical neutrinos, when they propagate through the Sun, can be significant. Though the flavor composition of high-energy neutrinos can be remarkably modified, it is quite challenging to observe such effects even in the next-generation of neutrino telescopes.

  • Light scalar dark matter at neutrino oscillation experiments
    arXiv:1803.01773
    JHEP 1804 (2018) 136

    by: Liao, Jiajun (Hawaii U.) et al.

    Abstract:
    Couplings between light scalar dark matter (DM) and neutrinos induce a perturbation to the neutrino mass matrix. If the DM oscillation period is smaller than ten minutes (or equivalently, the DM particle is heavier than $0.69\times10^{-17}$ eV), the fast-averaging over an oscillation cycle leads to a modification of the measured oscillation parameters. We present a specific $\mu-\tau$ symmetric model in which the measured value of $\theta_{13}$ is entirely generated by the DM interaction, and which reproduces the other measured oscillation parameters. For a scalar DM particle lighter than $10^{-15}$ eV, adiabatic solar neutrino propagation is maintained. A suppression of the sensitivity to CP violation at long-baseline neutrino experiments is predicted in this model. We find that DUNE cannot exclude the DM scenario at more than $3\sigma$ C.L. for bimaximal, tribimaximal and hexagonal mixing, while JUNO can rule it out at more than $6\sigma$ C.L. by precisely measuring both $\theta_{12}$ and $\theta_{13}$.

  • Neutrino-Electron Scattering: General Constraints on Z' and Dark Photon Models
    arXiv:1803.00060
    JHEP 1805 (2018) 098

    by: Lindner, Manfred (Heidelberg, Max Planck Inst.) et al.

    Abstract:
    We study the framework of $U(1)_X$ models with kinetic mixing and/or mass mixing terms. We give general and exact analytic formulas and derive limits on a variety of $U(1)_X$ models that induce new physics contributions to neutrino-electron scattering, taking into account interference between the new physics and Standard Model contributions. Data from TEXONO, CHARM-II and GEMMA are analyzed and shown to be complementary to each other to provide the most restrictive bounds on masses of the new vector bosons. In particular, we demonstrate the validity of our results to dark photon-like as well as light $Z^\prime$ models.

  • The Bright and Choked Gamma-Ray Burst Contribution to the IceCube and ANTARES Low-Energy Excess
    arXiv:1802.10098
    JCAP 1804 (2018) 058

    by: Denton, Peter B. (Copenhagen U.) et al.

    Abstract:
    The increasing statistics of the high-energy neutrino flux observed by the IceCube Observatory points towards an excess of events above the atmospheric neutrino background in the 30--400 TeV energy range. Such an excess is compatible with the findings of the ANTARES Telescope and it would naturally imply the possibility that more than one source class contributes to the observed flux. Electromagnetically hidden sources have been invoked to interpret this excess of events at low energies. By adopting a unified model for the electromagnetically bright and choked gamma-ray bursts and taking into account particle acceleration at the internal and collimation shock radii, we discuss whether bright and choked bursts are viable candidates. Our findings suggest that, although producing a copious neutrino flux, choked and bright astrophysical jets cannot be the dominant sources of the excess of neutrino events. A fine tuning of the model parameters or distinct scenarios for choked jets should be invoked in order to explain the low-energy neutrino data of IceCube and ANTARES.

  • A new leading contribution to neutrinoless double-beta decay
    LA-UR-18-21404
    NIKHEF-2018-010
    arXiv:1802.10097
    Phys.Rev.Lett. 120 (2018) 202001

    by: Cirigliano, Vincenzo (Los Alamos) et al.

    Abstract:
    Within the framework of chiral effective field theory we discuss the leading contributions to the neutrinoless double-beta decay transition operator induced by light Majorana neutrinos. Based on renormalization arguments in both dimensional regularization with minimal subtraction and a coordinate-space cutoff scheme, we show the need to introduce a leading-order short-range operator, missing in all current calculations. We discuss strategies to determine the finite part of the short-range coupling by matching to lattice QCD or by relating it via chiral symmetry to isospin-breaking observables in the two-nucleon sector. Finally, we speculate on the impact of this new contribution on nuclear matrix elements of relevance to experiment.

  • Strong thermal $SO(10)$-inspired leptogenesis in the light of recent results from long-baseline neutrino experiments
    arXiv:1802.07690
    JHEP 1805 (2018) 073

    by: Chianese, Marco (Southampton U.) et al.

    Abstract:
    We confront recent experimental results on neutrino mixing parameters with the requirements from strong thermal $SO(10)$-inspired leptogenesis, where the asymmetry is produced from next-to-lightest right-handed neutrinos $N_2$ independently of the initial conditions. There is a nice agreement with latest global analyses supporting $\sin\delta < 0$ and normal ordering at $ \sim 95\%$ C.L. On the other hand, the more stringent experimental lower bound on the atmospheric mixing angle starts to corner strong thermal $SO(10)$-inspired leptogenesis. Prompted and encouraged by this rapid experimental advance, we obtain a precise determination of the allowed region in the plane $\delta$ versus $\theta_{23}$. We confirm that for the benchmark case $\alpha_2 \equiv m_{D2} / m_{\rm charm}= 5 \, $, where $m_{D2}$ is the intermediate neutrino Dirac mass setting the $N_2$ mass, and initial pre-existing asymmetry $N_{B-L}^{\rm p, i} = 10^{-3}$, the bulk of solutions lies in the first octant. Though most of the solutions are found outside the $95\%$ C.L. experimental region, there is still a big allowed fraction that does not require a too fine-tuned choice of the Majorana phases so that the neutrinoless double beta decay effective neutrino mass allowed range is still $m_{ee}\simeq [10,30]\,{\rm meV}$. We also show how the constraints depend on $N_{B-L}^{\rm p, i}$ and $\alpha_2$. In particular, we show that the current best fit, ($\theta_{23},\delta)\simeq (47^{\circ}, -130^{\circ})$, can be reproduced for $N_{B-L}^{\rm p, i} = 10^{-3}$ and $\alpha_2 = 6$. Such large values for $\alpha_2$ have been recently obtained in a few realistic fits within $SO(10)$-inspired models. Finally, we also obtain that current neutrino data rule out $N_{B-L}^{\rm p, i} \gtrsim 0.1$ for $\alpha_2 \lesssim 4.7$.

  • Angular and polarization trails from effective interactions of Majorana neutrinos at the LHeC
    arXiv:1802.07620
    Eur.Phys.J. C78 (2018) 352

    by: Duarte, Lucía (Republica U., Montevideo) et al.

    Abstract:
    We study the possibility of the LHeC facility to disentangle different new physics contributions to the production of heavy sterile Majorana neutrinos in the lepton number violating channel $e^{-}p\rightarrow l_{j}^{+} + 3 \mathrm{jets}$ ( $l_j\equiv e ,\mu $ ). This is done investigating the angular and polarization trails of effective operators with distinct Dirac–Lorentz structure contributing to the Majorana neutrino production, which parameterize new physics from a higher energy scale. We study an asymmetry in the angular distribution of the final anti-lepton and the initial electron polarization effect on the number of signal events produced by the vectorial and scalar effective interactions, finding both analyses could well separate their contributions.

  • Seesaw roadmap to neutrino mass and dark matter
    IFIC-18-XXX
    arXiv:1802.05722
    Phys.Lett. B781 (2018) 122-128

    by: Centelles Chuliá, Salvador (Valencia U., IFIC) et al.

    Abstract:
    We describe the many pathways to generate Majorana and Dirac neutrino mass through generalized dimension-5 operators a la Weinberg . The presence of new scalars beyond the Standard Model Higgs doublet implies new possible field contractions, which are required in the case of Dirac neutrinos. We also notice that, in the Dirac neutrino case, the extra symmetries needed to ensure the Dirac nature of neutrinos can also be made responsible for stability of dark matter.

  • Non-thermal Leptogenesis after Majoron Hilltop Inflation
    arXiv:1802.05647
    JCAP 1805 (2018) 015

    by: Antusch, Stefan (Basel U.) et al.

    Abstract:
    We analyse non-thermal leptogenesis after models of Majoron hilltop inflation, where the scalar field that provides masses for the right-handed neutrinos and sneutrinos via its vacuum expectation value acts as the inflaton. We discuss different realisations of Majoron inflation models with different hilltop shapes and couplings to the right-handed (s)neutrinos. To study the non-thermally produced baryon asymmetry in these models, we numerically solve the relevant Boltzmann equations. In contrast to previous studies, we include the effects from resonant sneutrino particle production during preheating. We find that these effects can result in an enhancement of the produced baryon asymmetry by more than an order of magnitude. This can significantly change the favoured parameter regions of these models.

  • Probing neutrino coupling to a light scalar with coherent neutrino scattering
    arXiv:1802.05171
    JHEP 1805 (2018) 066

    by: Farzan, Yasaman (IPM, Tehran) et al.

    Abstract:
    Large neutrino event numbers in future experiments measuring coherent elastic neutrino nucleus scattering allow precision measurements of standard and new physics. We analyze the current and prospective limits of a light scalar particle coupling to neutrinos and quarks, using COHERENT and CONUS as examples. Both lepton number conserving and violating interactions are considered. It is shown that current (future) experiments can probe for scalar masses of a few MeV couplings down to the level of $10^{-4}$ $(10^{-6})$. Scalars with masses around the neutrino energy allow to determine their mass via a characteristic spectrum shape distortion. Our present and future limits are compared with constraints from supernova evolution, Big Bang nucleosynthesis and neutrinoless double beta decay. We also outline UV-complete underlying models that include a light scalar with coupling to quarks for both lepton number violating and conserving coupling to neutrinos.

  • Third Family Quark-Lepton Unification at the TeV Scale
    MITP-18-012
    arXiv:1802.04274
    Phys.Lett. B782 (2018) 131-138

    by: Greljo, Admir (Mainz U., Inst. Phys.) et al.

    Abstract:
    We construct a model of quark-lepton unification at the TeV scale based on an $SU(4)$ gauge symmetry, while still having acceptable neutrino masses and enough suppression in flavor changing neutral currents. An approximate $U(2)$ flavor symmetry is an artifact of family-dependent gauge charges leading to a natural realization of the CKM mixing matrix. The model predicts sizeable violation of PMNS unitarity as well as a gauge vector leptoquark $U_1^\mu = ({\bf 3}, {\bf 1}, 2/3)$ which can be produced at the LHC -- both effects within the reach of future measurements. In addition, recently reported experimental anomalies in semi-leptonic $B$-meson decays, both in charged $b \to c \tau \nu$ and neutral $b \to s \mu \mu$ currents, can be accommodated.

  • The possibility of leptonic CP-violation measurement with JUNO
    arXiv:1802.03677
    Nucl.Phys. B931 (2018) 437-445

    by: Smirnov, Mikhail
    Abstract:
    The existence of CP-violation in the leptonic sector is one of the most important issues for modern science. Neutrino physics is a key to the solution of this problem. JUNO (under construction) is the near future of neutrino physics. However CP-violation is not a priority for the current scientific program. We estimate the capability of $\delta_{\rm CP}$ measurement, assuming a combination of the JUNO detector and a superconductive cyclotron as the antineutrino source. This method of measuring CP-violation is an alternative to conventional beam experiments. A significance level of 3$\sigma$ can be reached for 22% of the $\delta_{\rm CP}$ range. The accuracy of measurement lies between 8$^{\rm o}$ and 22$^{\rm o}$. It is shown that the dominant influence on the result is the uncertainty in the mixing angle $\Theta_{23}$.

  • $T$-odd correlations in polarized top quark decays in the sequential decay $t(\uparrow) \to X_b+W^+(\to \ell^+ + \nu_\ell)$ and in the quasi three-body decay $t(\uparrow) \to X_b+ \ell^+ + \nu_\ell$
    MITP-18-002
    arXiv:1802.02492
    Phys.Rev. D97 (2018) 093001

    by: Fischer, M. (unlisted, DE) et al.

    Abstract:
    We identify the T-odd structure functions that appear in the description of polarized top quark decays in the sequential decay t(↑)→Xb+W+(→ℓ++νℓ) (two structure functions) and the quasi-three-body decay t(↑)→Xb+ℓ++νℓ (one structure function). A convenient measure of the magnitude of the T-odd structure functions is the contribution of the imaginary part ImgR of the right-chiral tensor coupling gR to the T-odd structure functions which we work out. Contrary to the case of QCD, the NLO electroweak corrections to polarized top quark decays admit absorptive one-loop vertex contributions. We analytically calculate the imaginary parts of the relevant four electroweak one-loop triangle vertex diagrams and determine their contributions to the T-odd helicity structure functions that appear in the description of polarized top quark decays.

  • Renormalization-Group Equations of Neutrino Masses and Flavor Mixing Parameters in Matter
    arXiv:1802.00990
    JHEP 1805 (2018) 015

    by: Xing, Zhi-zhong (Beijing, Inst. High Energy Phys.) et al.

    Abstract:
    We borrow the general idea of renormalization-group equations (RGEs) to understand how neutrino masses and flavor mixing parameters evolve when neutrinos propagate in a medium, highlighting a meaningful possibility that the genuine flavor quantities in vacuum can be extrapolated from their matter-corrected counterparts to be measured in some realistic neutrino oscillation experiments. Taking the matter parameter $a \equiv 2\sqrt{2} \ G^{}_{\rm F} N^{}_e E$ to be an arbitrary scale-like variable with $N^{}_e$ being the net electron number density and $E$ being the neutrino beam energy, we derive a complete set of differential equations for the effective neutrino mixing matrix $V$ and the effective neutrino masses $\widetilde{m}^{}_i$ (for $i = 1, 2, 3$). Given the standard parametrization of $V$, the RGEs for $\{\widetilde{\theta}^{}_{12}, \widetilde{\theta}^{}_{13}, \widetilde{\theta}^{}_{23}, \widetilde{\delta}\}$ in matter are formulated for the first time. We demonstrate some useful differential invariants which retain the same form from vacuum to matter, including the well-known Naumov and Toshev relations. The RGEs of the partial $\mu$-$\tau$ asymmetries, the off-diagonal asymmetries and the sides of unitarity triangles of $V$ are also obtained as a by-product.

  • Right-Handed Neutrinos: DM and LFV $vs$ Collider
    arXiv:1802.00944
    Nuovo Cim. C40 (2018) 165

    by: Chekkal, M. (Oran, Sci. Tech. U.) et al.

    Abstract:
    In a class of neutrino mass models with a lepton flavor violation (LFV) Yukawa interaction term that involves a heavy right handed neutrino, a charged scalar and a charged lepton, we investigate at the ILC@500 GeV the possibility of observing news physics. These models can address neutrino mass and dark matter without being in conflict with different LFV constraints. By imposing DM relic density and LFV constraints, we recast the analysis done by L3 collaboration at LEP-II of monophoton searches on our space parameter and look for new physics in such channels like monophoton and $S S(\gamma)$, where we give different cuts and show the predicted distributions. We show also that using polarized beams could improve the statistical significance.

  • Proceedings, 31st Rencontres de Physique de La Vallée d'Aoste (La Thuile): La Thuile, Aosta , Italy, March 5-11, 2017
    Nuovo Cim. C40 (2018)


  • Lepton-Number-Charged Scalars and Neutrino Beamstrahlung
    arXiv:1802.00009
    NUHEP-TH-18-03
    FERMILAB-PUB-18-020-T
    Phys.Rev. D97 (2018) 075030

    by: Berryman, Jeffrey M. (Virginia Tech.) et al.

    Abstract:
    Experimentally, baryon number minus lepton number, B-L, appears to be a good global symmetry of nature. We explore the consequences of the existence of gauge-singlet scalar fields charged under B-L–dubbed lepton-number-charged scalars (LeNCSs)—and postulate that these couple to the standard model degrees of freedom in such a way that B-L is conserved even at the nonrenormalizable level. In this framework, neutrinos are Dirac fermions. Including only the lowest mass-dimension effective operators, some of the LeNCSs couple predominantly to neutrinos and may be produced in terrestrial neutrino experiments. We examine several existing constraints from particle physics, astrophysics, and cosmology to the existence of a LeNCS carrying B-L charge equal to two, and discuss the emission of LeNCSs via “neutrino beamstrahlung,” which occurs every once in a while when neutrinos scatter off of ordinary matter. We identify regions of the parameter space where existing and future neutrino experiments, including the Deep Underground Neutrino Experiment, are at the frontier of searches for such new phenomena.

  • Probability Density Functions for CP-Violating Rephasing Invariants
    arXiv:1801.10165
    Nucl.Phys. B930 (2018) 384-398

    by: Fortin, Jean-François (Laval U.) et al.

    Abstract:
    The implications of the anarchy principle on CP violation in the lepton sector are investigated. A systematic method is introduced to compute the probability density functions for the CP-violating rephasing invariants of the PMNS matrix from the Haar measure relevant to the anarchy principle. Contrary to the CKM matrix which is hierarchical, it is shown that the Haar measure, and hence the anarchy principle, are very likely to lead to the observed PMNS matrix. Predictions on the CP-violating Dirac rephasing invariant |jD| and Majorana rephasing invariant |j1| are also obtained. They correspond to 〈|jD|〉Haar=π/105≈0.030 and 〈|j1|〉Haar=1/(6π)≈0.053 respectively, in agreement with the experimental hint from T2K of |jDexp|≈0.032±0.005 (or ≈0.033±0.003 ) for the normal (or inverted) hierarchy.

  • Neutrino conversion in a neutrino flux: Towards an effective theory of collective oscillations
    arXiv:1801.09751
    JCAP 1804 (2018) 057

    by: Hansen, Rasmus S.L. (Heidelberg, Max Planck Inst.) et al.

    Abstract:
    Collective oscillations of supernova neutrinos above the neutrino sphere can be completely described by the propagation of individual neutrinos in external potentials and are in this sense a linear phenomenon. An effective theory of collective oscillations can be developed based on certain assumptions about time dependence of these potentials. General conditions for strong flavor transformations are formulated and these transformations can be interpreted as parametric resonance effects induced by periodic modulations of the potentials. We study a simplified and solvable example, where a probe neutrino is propagating in a flux of collinear neutrinos, such that ν ν− interactions in the flux are absent. Still, this example retains the main feature—the coherent flavor exchange. Properties of the parametric resonance are studied, and it is shown that integrations over energies and emission points of the flux neutrinos suppress modulations of the potentials and therefore strong transformations. The transformations are also suppressed by changes in densities of background neutrinos and electrons.

  • Matter-neutrino resonance in a multiangle neutrino bulb model
    arXiv:1801.07813
    Phys.Rev. D97 (2018) 083011

    by: Vlasenko, A. (North Carolina State U.) et al.

    Abstract:
    Simulations of neutrino flavor evolution in compact merger environments have shown that neutrino flavor, and hence nucleosynthesis, can be strongly affected by the presence of matter-neutrino resonances (MNRs), where there is a cancelation between the matter and the neutrino potential. Simulations performed thus far follow flavor evolution along a single neutrino trajectory, but self-consistency requires all trajectories to be treated simultaneously, and it has not been known whether MNR phenomena would still occur in multiangle models. In this paper, we present the first fully multi-angle calculations of MNR. We find that familiar MNR phenomena, where neutrinos transform to a greater extent than anti-neutrinos and a feedback mechanism maintains the cancellation between the matter and neutrino potential, still occurs for a subset of angular bins, although the flavor transformation is not as efficient as in the single-angle case. In addition, we find other types of flavor transformation that are not seen in single-angle simulations. These flavor transformation phenomena appear to be robust and are present for a wide range of model parameters, as long as an MNR is present. Although computational constraints currently limit us to models with spherical symmetry, our results suggest that the presence of an MNR generally leads to large-scale neutrino flavor evolution in multiangle systems.

  • Charged Lepton Flavor Violation in a class of Radiative Neutrino Mass Generation Models
    arXiv:1801.07199
    Phys.Rev. D97 (2018) 075042

    by: Chowdhury, Talal Ahmed (Dhaka U.) et al.

    Abstract:
    We investigate the charged lepton flavor violating processes μ→eγ, μ→eee¯, and μ-e conversion in nuclei for a class of three-loop radiative neutrino mass generation models with electroweak multiplets of increasing order. We find that, because of certain cancellations among various one-loop diagrams which give the dipole and nondipole contributions in an effective μeγ vertex and a Z-penguin contribution in an effective μeZ vertex, the flavor violating processes μ→eγ and μ-e conversion in nuclei become highly suppressed compared to μ→eee¯ process. Therefore, the observation of such a pattern in LFV processes may reveal the radiative mechanism behind neutrino mass generation.

  • Majorana neutrino and the vacuum of Bogoliubov quasiparticle
    RIKEN-ITHEMS-REPORT-18
    arXiv:1801.06960
    Phys.Lett. B781 (2018) 295-301

    by: Fujikawa, Kazuo (Nishina Ctr., RIKEN)

    Abstract:
    The Lagrangian of the seesaw mechanism is C violating but the same Lagrangian when re-written in terms of Majorana neutrinos is manifestly C invariant. To resolve this puzzling feature, a relativistic analogue of Bogoliubov transformation, which preserves CP but explicitly breaks C and P separately, was introduced together with the notions of a Bogoliubov quasiparticle and an analogue of the energy gap in BCS theory. The idea of Majorana neutrino as Bogoliubov quasiparticle was then suggested. In this paper, we study the vacuum structure of the Bogoliubov quasiparticle which becomes heavy by absorbing the C-breaking. By treating an infinitesimally small C violating term as an analogue of the chiral symmetry breaking nucleon mass in the model of Nambu and Jona-Lasinio, we construct an explicit form of the vacuum of the Bogoliubov quasiparticle which defines Majorana neutrinos in seesaw mechanism. The vacuum of the Bogoliubov quasiparticle thus constructed has an analogous condensate structure as the vacuum of the quasiparticle (nucleon) in the Nambu–Jona-Lasinio model.

  • Longitudinal leading-twist distribution amplitude of the J/$\psi$ meson within the background field theory
    arXiv:1801.06832
    Phys.Rev. D97 (2018) 074025

    by: Fu, Hai-Bing (Guizhou Minzu U., Guiyang) et al.

    Abstract:
    We make a detailed study on the $J/\psi$ meson longitudinal leading-twist distribution amplitude $\phi_{2;J/\psi}^\|$ by using the QCD sum rules within the background field theory. By keeping all the non-perturbative condensates up to dimension-six, we obtain accurate QCD sum rules for the moments $\langle\xi_{n;J/\psi}^\|\rangle$. The first three ones are $\langle\xi_{2;J/\psi}^\|\rangle=0.083(12)$, $\langle\xi_{4;J/\psi}^\|\rangle=0.015(5)$ and $\langle\xi_{6;J/\psi}^\|\rangle=0.003(2)$, leading to a single peaked behavior for $\phi_{2;J/\psi}^\|$ which is sharper than the previous ones around the region of $x\sim0.5$. As an application, we adopt the QCD light-cone sum rules to calculate the $B_c$ meson semileptonic decay $B_c^+ \to J/\psi \ell^+ \nu_\ell$. We obtain $\Gamma(B_c^+ \to J/\psi \ell^+ \nu_\ell) = (89.67^{+24.76}_{-19.06}) \times 10^{-15}~{\rm GeV}$ and $\Re(J/\psi \ell^+ \nu_\ell) = 0.217^{+0.069}_{-0.057}$, which agree with the next-to-leading order pQCD prediction and the new CDF measurement within errors.

  • Self-interacting dark matter constraints in a thick dark disk scenario
    arXiv:1801.06556
    Phys.Rev. D97 (2018) 103003

    by: Vattis, Kyriakos (Brown U.) et al.

    Abstract:
    A thick dark matter disk is predicted in cold dark matter simulations as the outcome of the interaction between accreted satellites and the stellar disk in Milky Way–sized halos. We study the effects of a self-interacting thick dark disk on the energetic neutrino flux from the Sun. We find that for particle masses between 100 GeV and 1 TeV and dark matter annihilation to τ+τ-, either the self-interaction may not be strong enough to solve the small-scale structure motivation or a dark disk cannot be present in the Milky Way.

  • Predictions for the Dirac CP-Violating Phase from Sum Rules
    arXiv:1801.06377
    Phys.Rev. D97 (2018) 095001

    by: Delgadillo, Luis A. (Colima U.) et al.

    Abstract:
    We explore the implications of recent results relating the Dirac CP-violating phase to predicted and measured leptonic mixing angles within a standard set of theoretical scenarios in which charged lepton corrections are responsible for generating a nonzero value of the reactor mixing angle. We employ a full set of leptonic sum rules as required by the unitarity of the lepton mixing matrix, which can be reduced to predictions for the observable mixing angles and the Dirac CP-violating phase in terms of model parameters. These sum rules are investigated within a given set of theoretical scenarios for the neutrino sector diagonalization matrix for several known classes of charged lepton corrections. The results provide explicit maps of the allowed model parameter space within each given scenario and assumed form of charged lepton perturbations.

  • Comprehensive asymmetric dark matter model
    arXiv:1801.05561
    Phys.Rev. D97 (2018) 103510

    by: Lonsdale, Stephen J. (ARC, CoEPP, Melbourne) et al.

    Abstract:
    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical constraints. Importantly, it incorporates a deep reason for why the dark matter mass scale is related to the proton mass, a key consideration in ADM models. Our starting point is the idea of mirror matter, which offers an explanation for dark matter by duplicating the standard model with a dark sector related by a $Z_2$ parity symmetry. However, the dark sector need not manifest as a symmetric copy of the standard model in the present day. By utilising the mechanism of "asymmetric symmetry breaking" with two Higgs doublets in each sector, we develop a model of ADM where the mirror symmetry is spontaneously broken, leading to an electroweak scale in the dark sector that is significantly larger than that of the visible sector. The weak sensitivity of the ordinary and dark QCD confinement scales to their respective electroweak scales leads to the necessary connection between the dark matter and proton masses. The dark matter is composed of either dark neutrons or a mixture of dark neutrons and metastable dark hydrogen atoms. Lepton asymmetries are generated by the $CP$-violating decays of heavy Majorana neutrinos in both sectors. These are then converted by sphaleron processes to produce the observed ratio of visible to dark matter in the universe. The dynamics responsible for the kinetic decoupling of the two sectors emerges as an important issue that we only partially solve.

  • $\tau \to f_1 (1285)\pi^{-} \nu_{\tau}$ decay in the extended Nambu -- Jona-Lasinio model
    arXiv:1801.03148
    Eur.Phys.J. A54 (2018) 61

    by: Volkov, M.K. (Dubna, JINR) et al.

    Abstract:
    Within the framework of the extended Nambu-Jona-Lasinio model, we calculate the matrix element of the $\tau \rightarrow f_{1}(1285) \pi^{-} \nu_{\tau}$ decay, obtain the invariant mass distribution of the $ f_{1}\pi$ -system and estimate the branching ratio $\mathrm{Br}(\tau \rightarrow f_{1} \pi^{-}\nu_{\tau}) = 4.0\times 10^{-4}$ . The two types of contributions are considered: the contact interaction, and the axial-vector $I^{G}(J^{PC})=1^{-}(1^{++})$ resonance exchange. The latter includes the ground $a_{1}(1260)$ state, and its first radially excited state, $ a_{1}(1640)$ . The corrections caused by the $\pi$ - $a_{1}$ transitions are taken into account. Our estimate is in a good agreement with the latest empirical result $\mathrm{Br}(\tau \rightarrow f_{1} \pi^{-} \nu_{\tau})=(3.9\pm 0.5)\times 10^{-4}$ . The distribution function obtained for the decay $ \tau \rightarrow f_{1}(1285) \pi^{-} \nu_{\tau}$ shows a clear signal of $a_{1}(1640)$ resonance which should be compared with future experimental data including our estimate of the decay width $ \Gamma (a_{1}(1640) \rightarrow f_{1} \pi)=14.1$ MeV.

  • Antitriplet charmed baryon decays with SU(3) flavor symmetry
    arXiv:1801.03276
    Phys.Rev. D97 (2018) 073006

    by: Geng, C.Q. (Shanxi Normal U.) et al.

    Abstract:
    We study the decays of the antitriplet charmed baryon state (Ξc0,Ξc+,Λc+) based on the SU(3) flavor symmetry. In particular, after predicting B(Ξc0→Ξ-π+)=(15.7±0.7)×10-3 and B(Ξc+→Ξ-π+π+)=(14.7±8.4)×10-3, we extract that B(Ξc0→ΛK-π+,ΛK+K-,Ξ-e+νe)=(16.8±2.3,0.45±0.11,48.7±17.4)×10-3 and B(Ξc+→pKs0Ks0,Σ+K-π+,Ξ0π+π0,Ξ0e+νe)=(1.3±0.8,13.8±8.0,33.8±21.9,33.8-22.6+21.9)×10-3. We also find that B(Ξc0→Ξ0η,Ξ0η′)=(1.7-1.7+1.0,8.6-6.3+11.0)×10-3, B(Ξc0→Λ0η,Λ0η′)=(1.6-0.8+1.2,9.4-6.8+11.6)×10-4 and B(Ξc+→Σ+η,Σ+η′)=(28.4-6.9+8.2,13.2-11.9+24.0)×10-4. These Ξc decays with the branching ratios of O(10-4–10-3) are clearly promising to be observed by the BESIII and LHCb experiments.

  • Phenomenology of $\Xi_b \to \Xi_c\,\tau\,\nu$ decays
    arXiv:1801.02007
    Phys.Rev. D97 (2018) 073004

    by: Dutta, Rupak (Surat, SVNIT)

    Abstract:
    Deviations from the standard model prediction have been reported in various semileptonic B decays mediated via b→c charged-current interactions. In this context, we analyze corresponding semileptonic baryon decays Ξb→Ξcτν using the helicity formalism. We report numerical results on various observables such as the decay rate, ratio of branching ratios, lepton-side forward-backward asymmetry, longitudinal polarization fraction of the charged lepton, and the convexity parameter for this decay mode using results from the relativistic quark model. We also provide an estimate of the new physics effect on these observables under various new physics scenarios.

  • $A_4$ flavour model for Dirac neutrinos: Type I and inverse seesaw
    arXiv:1712.06407
    Phys.Lett. B780 (2018) 461-470

    by: Borah, Debasish (Indian Inst. Tech., Guwahati) et al.

    Abstract:
    We propose two different seesaw models namely, type I and inverse seesaw to realise light Dirac neutrinos within the framework of A4 discrete flavour symmetry. The additional fields and their transformations under the flavour symmetries are chosen in such a way that naturally predicts the hierarchies of different elements of the seesaw mass matrices in these two types of seesaw mechanisms. For generic choices of flavon alignments, both the models predict normal hierarchical light neutrino masses with the atmospheric mixing angle in the lower octant. Apart from predicting interesting correlations between different neutrino parameters as well as between neutrino and model parameters, the model also predicts the leptonic Dirac CP phase to lie in a specific range −π/3 to π/3 . While the type I seesaw model predicts smaller values of absolute neutrino mass, the inverse seesaw predictions for the absolute neutrino masses can saturate the cosmological upper bound on sum of absolute neutrino masses for certain choices of model parameters.

  • SU(5)$\times$U(1)$_X$ grand unification with minimal seesaw and $Z^\prime$-portal dark matter
    YGHP-17-10
    arXiv:1712.05290
    Phys.Lett. B780 (2018) 422-426

    by: Okada, Nobuchika (Alabama U.) et al.

    Abstract:
    We propose a grand unified SU(5)$\times$U(1)$_X$ model, where the standard SU(5) grand unified theory is supplemented by minimal seesaw and a right-handed neutrino dark matter with an introduction of a global $Z_2$-parity. In the presence of three right-handed neutrinos (RHNs), the model is free from all gauge and mixed-gravitational anomalies. The SU(5) symmetry is broken into the Standard Model (SM) gauge group at $M_{\rm GUT} \simeq 4 \times 10^{16}$ GeV in the standard manner, while the U(1)$_X$ symmetry breaking occurs at the TeV scale, which generates the TeV-scale mass of the U(1)$_X$ gauge boson ($Z^\prime$ boson) and the three Majorana RHNs. A unique $Z_2$-odd RHN is stable and serves as the dark matter (DM) in the present Universe, while the remaining two RHNs work to generate the SM neutrino masses through the minimal seesaw. We investigate the $Z^\prime$-portal RHN DM scenario in this model context, and find that the constraints from the DM relic abundance and the search results for a $Z^\prime$ boson resonance at the Large Hadron Collider (LHC) are complementary to narrow down the allowed parameter region, which will be fully covered by the future LHC experiments (for the $Z^\prime$ boson mass $<$ 5 TeV). We also briefly discuss the successful implementation of Baryogenesis and cosmological inflation scenarios in the present model.

  • Flavor and energy inference for the high-energy IceCube neutrinos
    arXiv:1712.04979
    Astropart.Phys. 101 (2018) 8-16

    by: D'Amico, Giacomo (Rome U.)

    Abstract:
    We present a flavor and energy inference analysis for each high-energy neutrino event observed by the IceCube observatory during six years of data taking. Our goal is to obtain, for the first time, an estimate of the posterior probability distribution for the most relevant properties, such as the neutrino energy and flavor, of the neutrino-nucleon interactions producing shower and track events in the IceCube detector. For each event the main observables in the IceCube detector are the deposited energy and the event topology (showers or tracks) produced by the Cherenkov light by the transit through a medium of charged particles created in neutrino interactions. It is crucial to reconstruct from these observables the properties of the neutrino which generated such event. Here we describe how to achieve this goal using Bayesian inference and Markov chain Monte Carlo methods.

  • Fermion masses and mixings and dark matter constraints in a model with radiative seesaw mechanism
    PI-UAN-2017-617FT
    LPT-ORSAY-17-75
    arXiv:1712.02792
    JHEP 1805 (2018) 053

    by: Bernal, Nicolás (Antonio Narino U.) et al.

    Abstract:
    We formulate a predictive model of fermion masses and mixings based on a $\Delta(27)$ family symmetry. In the quark sector the model leads to the viable mixing inspired texture where the Cabibbo angle comes from the down quark sector and the other angles come from both up and down quark sectors. In the lepton sector the model generates a predictive structure for charged leptons and, after radiative seesaw, an effective neutrino mass matrix with only one real and one complex parameter. We carry out a detailed analysis of the predictions in the lepton sector, where the model is only viable for inverted neutrino mass hierarchy, predicting a strict correlation between $\theta_{23}$ and $\theta_{13}$. We show a benchmark point that leads to the best-fit values of $\theta_{12}$, $\theta_{13}$, predicting a specific $\sin^2\theta_{23} \simeq 0.51$ (within the $3 \sigma$ range), a leptonic CP-violating Dirac phase $\delta \simeq 281.6 ^\circ$ and for neutrinoless double-beta decay $m_{ee} \simeq 41.3$ meV. We turn then to an analysis of the dark matter candidates in the model, which are stabilized by an unbroken $\mathbb{Z}_2$ symmetry. We discuss the possibility of scalar dark matter, which can generate the observed abundance through the Higgs portal by the standard WIMP mechanism. An interesting possibility arises if the lightest heavy Majorana neutrino is the lightest $\mathbb{Z}_2$-odd particle. The model can produce a viable fermionic dark matter candidate, but only as a feebly interacting massive particle (FIMP), with the smallness of the coupling to the visible sector protected by a symmetry and directly related to the smallness of the light neutrino masses.

  • Neutrinos, DUNE and the world best bound on CPT invariance
    FTUV-17-11-29
    IFIC-17-57
    arXiv:1712.01714
    Phys.Lett. B780 (2018) 631-637

    by: Barenboim, Gabriela (Valencia U.) et al.

    Abstract:
    CPT symmetry, the combination of Charge Conjugation, Parity and Time reversal, is a cornerstone of our model building strategy and therefore the repercussions of its potential violation will severely threaten the most extended tool we currently use to describe physics, i.e. local relativistic quantum fields. However, limits on its conservation from the Kaon system look indeed imposing. In this work we will show that neutrino oscillation experiments can improve this limit by several orders of magnitude and therefore are an ideal tool to explore the foundations of our approach to Nature. Strictly speaking testing CPT violation would require an explicit model for how CPT is broken and its effects on physics. Instead, what is presented in this paper is a test of one of the predictions of CPT conservation, i.e., the same mass and mixing parameters in neutrinos and antineutrinos. In order to do that we calculate the current CPT bound on all the neutrino mixing parameters and study the sensitivity of the DUNE experiment to such an observable. After deriving the most updated bound on CPT from neutrino oscillation data, we show that, if the recent T2K results turn out to be the true values of neutrino and antineutrino oscillations, DUNE would measure the fallout of CPT conservation at more than 3$\sigma$. Then, we study the sensitivity of the experiment to measure CPT invariance in general, finding that DUNE will be able to improve the current bounds on $\Delta(\Delta m^2_{31})$ by at least one order of magnitude. We also study the sensitivity to the other oscillation parameters. Finally we show that, if CPT is violated in nature, combining neutrino with antineutrino data in oscillation analysis will produce imposter solutions.

  • Model with a gauged lepton flavor SU(2) symmetry
    KUNS-2707
    arXiv:1712.00574
    JHEP 1805 (2018) 069

    by: Chiang, Cheng-Wei (Taiwan, Inst. Phys.) et al.

    Abstract:
    We propose a model having a gauged SU(2) symmetry associated with the second and third generations of leptons, dubbed SU(2)$_{μτ}$ , of which $ \mathrm{U}{(1)}_{{\mathbb{L}}_{\mu }-{\mathbb{L}}_{\tau }} $ is an Abelian subgroup. In addition to the Standard Model fields, we introduce two types of scalar fields. One exotic scalar field is an SU(2)$_{μτ}$ doublet and SM singlet that develops a nonzero vacuum expectation value at presumably multi-TeV scale to completely break the SU(2)$_{μτ}$ symmetry, rendering three massive gauge bosons. At the same time, the other exotic scalar field, carrying electroweak as well as SU(2)$_{μτ}$ charges, is induced to have a nonzero vacuum expectation value as well and breaks mass degeneracy between the muon and tau. We examine how the new particles in the model contribute to the muon anomalous magnetic moment in the parameter space compliant with the Michel decays of tau.

  • The semileptonic baryonic decay $D_s^+\to p\bar p e^+ \nu_e$
    arXiv:1712.00566
    Phys.Lett. B780 (2018) 100-105

    by: Cheng, Hai-Yang (Taiwan, Inst. Phys.) et al.

    Abstract:
    The decay Ds+→pp¯e+νe with a proton–antiproton pair in the final state is unique in the sense that it is the only semileptonic baryonic decay which is physically allowed in the charmed meson sector. Its measurement will test our basic knowledge on semileptonic Ds+ decays and the low-energy pp¯ interactions. Taking into account the major intermediate state contributions from η,η′,f0(980) and X(1835) , we find that its branching fraction is at the level of 10−9∼10−8 . The location and the nature of X(1835) state are crucial for the precise determination of the branching fraction. We wish to trigger a new round of a careful study with the upcoming more data in BESIII as well as the future super tau-charm factory.

  • A model explaining neutrino masses and the DAMPE cosmic ray electron excess
    CP3-ORIGINS-2017-056-DNRF90
    NCTS-PH-1727
    arXiv:1711.10995
    Phys.Lett. B781 (2018) 83-87

    by: Fan, Yi-Zhong (Hefei, CUST) et al.

    Abstract:
    We propose a flavored $U(1)_{e\mu}$ neutrino mass and dark matter~(DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under the new $U(1)_{e\mu}$ gauge symmetry. A vector-like fermion $\psi$, which is our DM candidate, annihilates into $e^{\pm}$ and $\mu^{\pm}$ via the new gauge boson $Z'$ exchange and accounts for the DAMPE excess. We have found that the data favors a $\psi$ mass around 1.5~TeV and a $Z'$ mass around 2.6~TeV, which can potentially be probed by the next generation lepton colliders and DM direct detection experiments.

  • Measuring the Sterile Neutrino CP Phase at DUNE and T2HK
    arXiv:1711.07464
    Eur.Phys.J. C78 (2018) 339

    by: Choubey, Sandhya (Harish-Chandra Res. Inst.) et al.

    Abstract:
    The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase $\delta _{24}$ affects the charged-current electron appearance data in long-baseline experiment. In this paper we show how well the sterile neutrino phase $\delta _{24}$ can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. The T2HK experiment is seen to be able to measure the sterile phase $\delta _{24}$ to a reasonable precision. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.

  • Can one ever prove that neutrinos are Dirac particles?
    IFIC-17-XX
    arXiv:1711.06181
    Phys.Lett. B781 (2018) 302-305

    by: Hirsch, Martin (Valencia U., IFIC) et al.

    Abstract:
    According to the “Black Box” theorem the experimental confirmation of neutrinoless double beta decay ( 0ν2β ) would imply that at least one of the neutrinos is a Majorana particle. However, a null 0ν2β signal cannot decide the nature of neutrinos, as it can be suppressed even for Majorana neutrinos. In this letter we argue that if the null 0ν2β decay signal is accompanied by a 0ν4β quadruple beta decay signal, then at least one neutrino should be a Dirac particle. This argument holds irrespective of the underlying processes leading to such decays.

  • Dark matter-neutrino interactions through the lens of their cosmological implications
    IFIC-17-54
    IPPP-17-84
    arXiv:1711.05283
    Phys.Rev. D97 (2018) 075039

    by: Olivares-Del Campo, Andrés (Durham U., IPPP) et al.

    Abstract:
    Dark matter and neutrinos provide the two most compelling pieces of evidence for new physics beyond the Standard Model of particle physics, but they are often treated as two different sectors. The aim of this paper is to determine whether there are viable particle physics frameworks in which dark matter can be coupled to active neutrinos. We use a simplified model approach to determine all possible scenarios where there is such a coupling and study their astrophysical and cosmological signatures. We find that dark matter–neutrino interactions have an impact on structure formation and lead to indirect detection signatures when the coupling between dark matter and neutrinos is sufficiently large. This can be used to exclude a large fraction of the parameter space. In most cases, dark matter masses up to a few MeV and mediator masses up to a few GeV are ruled out. The exclusion region can be further extended when dark matter is coupled to a spin-1 mediator or when the dark matter particle and the mediator are degenerate in mass if the mediator is a spin-0 or spin-1/2 particle.

  • A radiative seesaw model with higher order terms under an alternative $U(1)_{B-L}$
    KIAS-P17120
    arXiv:1711.05115
    Phys.Lett. B781 (2018) 561-567

    by: Nomura, Takaaki (Korea Inst. Advanced Study, Seoul) et al.

    Abstract:
    We propose a model based on an alternative $U(1)_{B-L}$ gauge symmetry with 5 dimensional operators in the Lagrangian, and we construct the neutrino masses at one-loop level, and discuss lepton flavor violations, dark matter, and the effective number of neutrino species due to two massless particles in our model. Then we search allowed region to satisfy the current experimental data of neutrino oscillation and lepton flavor violations without conflict of several constraints such as stability of dark matter and the effective number of neutrino species, depending on normal hierarchy and inverted one.

  • Lepton-Number Violation: Seesaw Models and Their Collider Tests
    PITT-PACC-1712
    IPPP-17-74
    COEPP-MN-17-17
    arXiv:1711.02180
    Front.in Phys. 6 (2018) 40

    by: Cai, Yi (SYSU, Guangzhou) et al.

    Abstract:
    The Majorana nature of neutrinos is strongly motivated from the theoretical and phenomenological point of view. A plethora of neutrino mass models, known collectively as Seesaw models, exist that could generate both a viable neutrino mass spectrum and mixing pattern. They can also lead to rich, new phenomenology, including lepton number non-conservation as well as new particles, that may be observable at collider experiments. It is therefore vital to search for such new phenomena and the mass scale associated with neutrino mass generation at high energy colliders. In this review, we consider a number of representative Seesaw scenarios as phenomenological benchmarks, including the characteristic Type I, II, and III Seesaw mechanisms, their extensions and hybridizations, as well as radiative constructions. We present new and updated predictions for analyses featuring lepton number violation and expected coverage in the theory parameter space at current and future colliders. We emphasize new production and decay channels, their phenomenological relevance and treatment across different facilities in $e^+e^-$, $e^-p$ and $pp$ collisions, as well as the available Monte Carlo tools available for studying Seesaw partners in collider environments.

  • Prospects of Indirect Searches for Dark Matter at INO
    arXiv:1711.02546
    JCAP 1805 (2018) 006

    by: Choubey, Sandhya (Harish-Chandra Res. Inst.) et al.

    Abstract:
    The annihilation of Weakly Interactive Massive Particles (WIMP) in the centre of the sun could give rise to neutrino fluxes. We study the prospects of searching for these neutrinos at the upcoming Iron CALorimeter (ICAL) detector to be housed at the India-based Neutrino Observatory (INO). We perform ICAL simulations to obtain the detector efficiencies and resolutions in order to simulate muon events in ICAL due to neutrinos coming from annihilation of WIMP in the mass range $m_\chi = (3-100)$ GeV. The atmospheric neutrinos pose a major background for these indirect detection studies and can be reduced using the fact that the signal comes only from the direction of the sun. For a given WIMP mass, we find the opening angle $\theta_{90}$ such that 90 \% of the signal events are contained within this angle and use this cone-cut criteria to reduce the atmospheric neutrino background. The reduced background is then weighted by the solar exposure function at INO to obtain the final background spectrum for a given WIMP mass. We perform a $\chi^2$ analysis and present expected exclusion regions in the $\sigma_{SD}-m_\chi$ and $\sigma_{SI}-m_\chi$, where $\sigma_{SD}$ and $\sigma_{SI}$ are the WIMP-nucleon Spin-Dependent (SD) and Spin-Independent (SI) scattering cross-section, respectively. For a 10 years exposure and $m_\chi=25$ GeV, the expected 90 \% C.L. exclusion limit is found to be $\sigma_{SD} < 6.87\times 10^{-41}$ cm$^2$ and $\sigma_{SI} < 7.75\times 10^{-43}$ cm$^2$ for the $\tau^{+} \tau^{-}$ annihilation channel and $\sigma_{SD} < 1.14\times 10^{-39}$ cm$^2$ and $\sigma_{SI} < 1.30\times 10^{-41}$ cm$^2$ for the $b~\bar b $ channel, assuming 100 \% branching ratio for each of the WIMP annihilation channel.

  • Clockwork for Neutrino Masses and Lepton Flavor Violation
    TUM-HEP-1107-17
    KIAS-P17115
    arXiv:1711.02070
    Phys.Lett. B780 (2018) 86-92

    by: Ibarra, Alejandro (Munich, Tech. U.) et al.

    Abstract:
    We investigate the generation of small neutrino masses in a clockwork framework which includes Dirac mass terms as well as Majorana mass terms for the new fermions. We derive analytic formulas for the masses of the new particles and for their Yukawa couplings to the lepton doublets, in the scenario where the clockwork parameters are universal. When the universal Majorana mass vanishes, the zero mode of the clockwork sector forms a Dirac pair with the active neutrino, with a mass which is in agreement with oscillations experiments for a sufficiently large number of clockwork gears. On the other hand, when it does not vanish, neutrino masses are generated via the seesaw mechanism. In this case, and due to the fact that the effective Yukawa couplings of the higher modes can be sizable, neutrino masses can only be suppressed by postulating a large Majorana mass scale. Finally, we discuss the constraints on the mass scale of the clockwork fermions from the non-observation of the rare leptonic decay μ→eγ .

  • Neutrino masses, dark matter and leptogenesis with $U(1)_{B-L}$ gauge symmetry
    arXiv:1710.09536
    Phys.Dark Univ. 20 (2018) 13-19

    by: Geng, Chao-Qiang (Shanxi Normal U.) et al.

    Abstract:
    We propose a model with an $U(1)_{B-L}$ gauge symmetry, in which small neutrino masses, dark matter and the matter-antimatter asymmetry in the Universe can be simultaneously explained. In particular, the neutrino masses are generated radiatively, while the matter-antimatter asymmetry is led by the leptogenesis mechanism, at TeV scale. We also explore allowed regions of the model parameters and discuss some phenomenological effects including lepton flavor violating processes.

  • The Dark Side of Flipped Trinification
    IFIC-17-XX
    arXiv:1710.06951
    JHEP 1804 (2018) 143

    by: Dong, P.V. (Hanoi, Inst. Phys.) et al.

    Abstract:
    We propose a model which unifies the Left-Right symmetry with the $SU(3)_L$ gauge group, called flipped trinification, and based on the $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_X$ gauge group. The model inherits the interesting features of both symmetries while elegantly explaining the origin of the matter parity, $W_P=(-1)^{3(B-L)+2s}$, and dark matter stability. We develop the details of the spontaneous symmetry breaking mechanism in the model, determining the relevant mass eigenstates, and showing how neutrino masses are easily generated via the seesaw mechanism. Viable dark matter candidates can either be a fermion, a scalar or a vector, leading to potentially different dark matter phenomenology.

  • Quasi Dirac neutrino oscillations
    IFIC-17-45
    arXiv:1710.06249
    Phys.Rev. D97 (2018) 095008

    by: Anamiati, G. (Valencia U., IFIC) et al.

    Abstract:
    Dirac neutrino masses require two distinct neutral Weyl spinors per generation, with a special arrangement of masses and interactions with charged leptons. Once this arrangement is perturbed, lepton number is no longer conserved and neutrinos become Majorana particles. If these lepton number violating perturbations are small compared to the Dirac mass terms, neutrinos are quasi-Dirac particles. Alternatively, this scenario can be characterized by the existence of pairs of neutrinos with almost degenerate masses, and a lepton mixing matrix which has 12 angles and 12 phases. In this work we discuss the phenomenology of quasi-Dirac neutrino oscillations and derive limits on the relevant parameter space from various experiments. In one parameter perturbations of the Dirac limit, very stringent bounds can be derived on the mass splittings between the almost degenerate pairs of neutrinos. However, we also demonstrate that with suitable changes to the lepton mixing matrix, limits on such mass splittings are much weaker, or even completely absent. Finally, we consider the possibility that the mass splittings are too small to be measured and discuss bounds on the new, nonstandard lepton mixing angles from current experiments for this case.

  • Detectability of thermal neutrinos from binary-neutron-star mergers and implication to neutrino physics
    arXiv:1710.05922
    Phys.Rev. D97 (2018) 103001

    by: Kyutoku, Koutarou (Sokendai, Tsukuba) et al.

    Abstract:
    We propose a long-term strategy for detecting thermal neutrinos from the remnant of binary neutron-star mergers with a future M-ton water-Cherenkov detector such as Hyper-Kamiokande. Monitoring ≳2500 mergers within ≲200  Mpc, we may be able to detect a single neutrino with a human time-scale operation of ≈80  Mtyears for the merger rate of 1  Mpc-3  Myr-1, which is slightly lower than the median value derived by the LIGO-Virgo Collaboration with GW170817. Although the number of neutrino events is minimal, contamination from other sources of neutrinos can be reduced efficiently to ≈0.03 by analyzing only ≈1  s after each merger identified with gravitational-wave detectors if gadolinium is dissolved in the water. The contamination may be reduced further to ≈0.01 if we allow the increase of waiting time by a factor of ≈1.7. The detection of even a single neutrino can pin down the energy scale of thermal neutrino emission from binary neutron-star mergers and could strongly support or disfavor formation of remnant massive neutron stars. Because the dispersion relation of gravitational waves is now securely constrained to that of massless particles with a corresponding limit on the graviton mass of ≲10-22  eV/c2 by binary black-hole mergers, the time delay of a neutrino from gravitational waves can be used to put an upper limit of ≲O(10)  meV/c2 on the absolute neutrino mass in the lightest eigenstate. Large neutrino detectors will enhance the detectability, and, in particular, 5 Mt Deep-TITAND and 10 Mt MICA planned in the future will allow us to detect thermal neutrinos every ≈16 and 8 years, respectively, increasing the significance.

  • Four-body decays of $B$ meson with lepton number violation
    arXiv:1710.03886
    J.Phys. G45 (2018) 065002

    by: Yuan, Han (Harbin Inst. Tech.) et al.

    Abstract:
    This paper is designed to calculate the branching ratio of four-body decays of $B$ meson with lepton number changed by 2. With the new experimental data limit to lepton-number violation processes, we update the upper limits of mixing parameters between heavy Majorana neutrino and charged leptons. Afterwards, we calculate the branching ratio of $B^0(P)\rightarrow D^{*-}(P_1)\ell^+_1(P_2)\ell^+_2(P_3)M_2^-(P_4)$ using the updated parameters. It is found that the most hopeful decay channel is $B^0(P)\rightarrow D^{*-}(P_1)e^+_1(P_2)e^+_2(P_3)\rho^-(P_4)$ or $B^0(P)\rightarrow D^{*-}(P_1)e(\mu)^+_1(P_2)\mu(e)^+_2(P_3)\rho^-(P_4)$, whose branching ratio can reach about $10^{-4}$ with heavy Majorana neutrino mass range around $2~\mathrm{GeV}$.

  • Radiative Neutrino Mass & Majorana Dark Matter within an Inert Higgs Doublet Model
    arXiv:1710.03824
    Phys.Rev. D97 (2018) 095012

    by: Ahriche, Amine (Shanghai Jiaotong U., INPAC) et al.

    Abstract:
    We consider an extension of the standard model (SM) with an inert Higgs doublet and three Majorana singlet fermions to address both origin and the smallness of neutrino masses and dark matter (DM) problems. In this setup, the lightest Majorana singlet fermion plays the role of DM candidate and the model parameter space can be accommodated to avoid different experimental constraints such as lepton flavor violating processes and electroweak precision tests. The neutrino mass is generated at one-loop level a la Scotogenic model and its smallness is ensured by the degeneracy between the CP-odd and CP-even scalar members of the inert doublet. Interesting signatures at both leptonic and hadronic colliders are discussed.

  • Neutrino oscillation processes in a quantum-field-theoretical approach
    arXiv:1709.09915
    Phys.Rev. D97 (2018) 093002

    by: Egorov, Vadim O. (SINP, Moscow) et al.

    Abstract:
    It is shown that neutrino oscillation processes can be consistently described in the framework of quantum field theory using only the plane wave states of the particles. Namely, the oscillating electron survival probabilities in experiments with neutrino detection by charged-current and neutral-current interactions are calculated in the quantum field–theoretical approach to neutrino oscillations based on a modification of the Feynman propagator in the momentum representation. The approach is most similar to the standard Feynman diagram technique. It is found that the oscillating distance-dependent probabilities of detecting an electron in experiments with neutrino detection by charged-current and neutral-current interactions exactly coincide with the corresponding probabilities calculated in the standard approach.

  • Hidden $U(1)$ gauge symmetry realizing a neutrinophilic two-Higgs-doublet model with dark matter
    KIAS-P17069
    arXiv:1709.06406
    Phys.Rev. D97 (2018) 075038

    by: Nomura, Takaaki (Korea Inst. Advanced Study, Seoul) et al.

    Abstract:
    We propose a neutrinophilic two-Higgs-doublet model with hidden local U(1) symmetry, where active neutrinos are Dirac type, and a fermionic dark matter (DM) candidate is naturally induced as a result of remnant symmetry even after the spontaneous symmetry breaking. In addition, a physical Goldstone boson arises as a consequence of two types of gauge singlet bosons and contributes to the DM phenomenologies as well as an additional neutral gauge boson. Then, we analyze the relic density of DM within the safe range of direct detection searches and show the allowed region of dark matter mass.

  • Asymptotically Safe Standard Model Extensions?
    CERN-TH-2017-173
    CP3-ORIGINS-2017-029
    IPPP-17-61
    CERN-{TH}-2017-173
    arXiv:1708.00437
    IFUP-TH-2017
    Phys.Rev. D97 (2018) 095013

    by: Pelaggi, Giulio Maria (INFN, Pisa) et al.

    Abstract:
    We consider theories with a large number $N_F$ of charged fermions and compute the renormalisation group equations for the gauge, Yukawa and quartic couplings resummed at leading order in $1/N_F$. We construct extensions of the Standard Model where SU(2) and/or SU(3) are asymptotically safe. When the same procedure is applied to the Abelian U(1) factor, we find that the Higgs quartic can not be made asymptotically safe and stay perturbative at the same time.

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