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  • Status and prospects of `bi-large' leptonic mixing

    by: Ding, Gui-Jun
    Bi-large patterns for the leptonic mixing matrix are confronted with current neutrino oscillation data. We analyse the status of these patterns and determine, through realistic simulations, the potential of upcoming long-baseline experiment DUNE in testing bi-large \emph{ansatze} and discriminating amongst them.

  • Several Problems in Particle Physics and Cosmology Solved in One SMASH
    DESY 19-056

    by: Ballesteros, Guillermo
    The Standard Model (SM) of particle physics is a big success. However, it lacks explanations for cosmic inflation, the matter-anti-matter asymmetry of the Universe, dark matter, neutrino oscillations, and the feebleness of CP violation in the strong interactions. The latter may be explained by a complex scalar field charged under a spontaneously broken global U(1) Peccei-Quinn (PQ) symmetry. Moreover, the pseudo Nambu-Goldstone boson of this breaking -- the axion -- may play the role of the dark matter. Furthermore, the modulus of the PQ field is a candidate for driving inflation. If additionally three extra SM singlet neutrinos (whose mass is induced by the PQ field) are included, the five aforementioned problems can be addressed at once. We review the SM extension dubbed SMASH -for SM-Axion-Seesaw-Higgs portal inflation-, discuss its predictions and tests in astrophysics, cosmology, and laboratory experiments. Variants of SMASH are also considered and commented on.

  • A $\pmb{\nu}$ Solution to the Strong CP Problem

    by: Carena, Marcela (Fermilab) et al.

    We present a new solution to the strong CP problem in which the imaginary component of the up quark mass, $\mathcal{I}[m_u]$, acquires a tiny, but non-vanishing value. This is achieved via a Dirac seesaw mechanism, which is also responsible for the generation of the small neutrino masses. Consistency with the observed value of the up quark mass is achieved via instanton contributions arising from QCD-like interactions. In this framework, the value of the neutron electric dipole moment is directly related to $\mathcal{I}[m_u]$, which, due to its common origin with the neutrino masses, implies that the neutron electric dipole moment is likely to be measured in the next round of experiments. We also present a supersymmetric extension of this Dirac seesaw model to stabilize the hierarchy among the scalar mass scales involved in this new mechanism.

  • Common origin of modified chaotic inflation, non thermal dark matter and Dirac neutrino mass

    by: Borah, Debasish
    We propose a minimal extension of the standard model of particle physics to accommodate cosmic inflation, dark matter and light neutrino masses. While the inflationary phase is obtained from a modified chaotic inflation scenario, consistent with latest cosmology data at $2\sigma$ level, the dark matter particle is a fermion singlet which remain out of equilibrium in the early universe. The scalar field which revives the chaotic inflation scenario by suitable modification also assists in generating tiny couplings of dark matter with its mother particle, naturally realising the non-thermal or freeze-in type dark matter scenario. Interestingly, the same assisting scalar field also helps in realising tiny Yukawa couplings required to generate sub-eV Dirac neutrino mass from neutrino couplings to the standard model like Higgs field. The minimality as well as providing a unified solution to all three problems keep the model predictive at experiments spanning out to all frontiers.

  • Minimal Two-component Scalar Doublet Dark Matter with Radiative Neutrino Mass

    by: Borah, Debasish
    We propose a minimal extension of the Standard Model to accommodate two-component dark matter (DM) and light neutrino mass. The symmetry of the Standard Model is enhanced by an unbroken $\mathbb{Z}_2 \times \mathbb{Z}'_2$ such that being odd under each $\mathbb{Z}_2$, there exists one right handed neutrino and one inert scalar doublet. Therefore, each of the $\mathbb{Z}_2$ sectors contribute to ($i$) light neutrino masses radiatively similar to the scotogenic models while ($ii$) the two neutral CP even scalars present in two additional inert doublets play the role of dark matters. Focussing on the intermediate range of inert scalar doublet DM scenario: $M_W \leq M_{\rm DM} \lesssim 500 \; {\rm GeV}$, where one scalar doublet DM can not satisfy correct relic, we show that this entire range becomes allowed within this two-component scalar doublet DM, thanks to the inter-conversion between the two DM candidates in presence of neutrino Yukawa couplings with dark sector.

  • Probing heavy neutrino mixing and associated CP violation at future hadron colliders

    by: Dev, P.S. Bhupal
    Heavy neutrinos are essential ingredients in the type-I seesaw mechanism for neutrino masses. Mixing and CP violation in the heavy neutrino sector therefore not only translate into neutrino oscillation parameters but also play an important role in generating the observed baryon asymmetry of the universe via leptogenesis. We show that future hadron colliders can directly access these mixing angles and CP phases in the heavy neutrino sector if type-I seesaw is embedded in a TeV-scale left-right model, by measuring the charge asymmetries in same-sign dilepton signals, e.g. $e^+ e^+$ versus $e^- e^-$, arising from $W_R$-mediated heavy neutrino production and subsequent decays. This provides a new way to test low-scale leptogenesis at future colliders.

  • Hidden Cores of Active Galactic Nuclei as the Origin of Medium-Energy Neutrinos: Critical Tests with the MeV Gamma-Ray Connection

    by: Murase, Kohta
    The cores of active galactic nuclei (AGNs) are among the candidate sources of the IceCube neutrinos, but the underlying cosmic-ray acceleration processes are unclear. Based on the standard disk-corona picture of AGNs, we present a phenomenological model, in which protons are stochastically accelerated by turbulence from the magnetorotational instability. We show that this model can explain a large diffuse flux of about 30 TeV neutrinos if the cosmic rays carry a few percent of the coronal thermal energy. We find that the Bethe-Heitler process plays a crucial role in connecting these neutrinos and cascaded MeV gamma rays, and point out that the gamma-ray flux can be even enhanced by reacceleration of secondary pairs. Critical tests of the model are given by its prediction that a significant fraction of the MeV gamma-ray background correlates with the 10 TeV neutrino background, and nearby Seyfert galaxies should be seen by future MeV gamma-ray telescopes.

  • A modular $A_4$ symmetric model of dark matter and neutrino
    APCTP Pre2019 - 007

    by: Nomura, Takaaki
    We propose a model based on modular $A_4$ symmetry containing a dark matter candidate and realizing radiatively induced neutrino mass at one-loop level. One finds that stability of dark matter candidate can be assured by nonzero value of modular weight and its mass tends to be much smaller than the other two masses in the triplet fields under the $A_4$ group. Therefore we clearly identify single dark matter field in this kind of model. Then we discuss several phenomenological aspects.

  • Raman stimulated neutrino pair emission

    by: Hara, H.
    A new scheme using macroscopic coherence is proposed from a theoretical point to experimentally determine the neutrino mass matrix, in particular the absolute value of neutrino masses, and the mass type, Majorana or Dirac. The proposed process is a collective, coherent Raman scattering followed by neutrino-pair emission from an excited state $|e\rangle$ of a long lifetime to a lower energy state $|g\rangle$; $\gamma_0 + | e\rangle \rightarrow \gamma + \sum_{ij} \nu_i \bar{\nu_j} + | g\rangle $ with $ \nu_i \bar{\nu_j}$ consisting of six massive neutrino-pairs. Calculated angular distribution has six $(ij)$ thresholds of massive neutrino-pair emission which show up as steps at different angles in the distribution. Angular locations of thresholds and event rates of the angular distribution make it possible to experimentally determine the smallest neutrino mass to the level of less than 1 meV (accordingly all three masses using neutrino oscillation data) , the mass ordering pattern , normal or inverted, and to distinguish whether neutrinos are of Majorana or Dirac type. Event rates of neutrino-pair emission, when the mechanism of macroscopic coherence amplification works, may become large enough for realistic experiments by carefully selecting certain types of target atoms or ions doped in crystals. The problem to be overcome is macro-coherently amplified quantum electrodynamic background of the process, $\gamma_0 + | e\rangle \rightarrow \gamma +\gamma_2 + \gamma_3+ | g\rangle $, when two extra photons, $\gamma_2\,, \gamma_3$, escape detection. We illustrate our idea using neutral Xe and trivalent Ho ion doped in dielectric crystals.

  • On coherent neutrino and antineutrino scattering off nuclei

    by: Bednyakov, Vadim A.
    Neutrino-nucleus $\nu A\to \nu A$ and antineutrino-nucleus $\bar\nu A\to \bar\nu A$ interactions, when the nucleus conserves its integrity, are discussed with coherent (elastic) and incoherent (inelastic) scattering regimes taken into account. In the first regime the nucleus remains in the same quantum state after the scattering and the cross-section depends on the quadratic number of nucleons. In the second regime the nucleus changes its quantum state and the cross-section has an essentially linear dependence on the number of nucleons. The coherent and incoherent cross-sections are driven by a nuclear nucleon form-factor squared $|F|^2$ term and a $(1-|F|^2)$ term, respectively. One has a smooth transition between the regimes of coherent and incoherent (anti)neutrino-nucleus scattering. Due to the neutral current nature these elastic and inelastic processes are indistinguishable if the nucleus recoil energy is only observed. One way to separate the coherent signal from the incoherent one is to register $\gamma$ quanta from deexcitation of the nucleus excited during the incoherent scattering. Another way is to use a very low-energy threshold detector and collect data at very low recoil energies, where the incoherent scattering is vanishingly small. In particular, for ${}^{133}\text{Cs}$ and neutrino energies of 30--50 MeV the incoherent cross-section is about 15-20\% of the coherent one. Therefore, the COHERENT experiment (with ${}^{133}\text{Cs}$) has measured the coherent elastic neutrino nucleus scattering (CE$\nu$NS) with the inelastic admixture at a level of 15-20\%, if the excitation $\gamma$ quantum escapes its detection.

  • 21-cm observations and warm dark matter models

    by: Boyarsky, Alexey
    Observations of the redshifted 21-cm signal (in absorption or emission) allow us to peek into the epoch of "dark ages" and the onset of reionization. These data can provide a novel way to learn about the nature of dark matter, in particular about the formation of small size dark matter halos. However, the connection between the formation of structures and 21-cm signal requires knowledge of stellar to total mass relation, escape fraction of UV photons, and other parameters that describe star formation and radiation at early times. This baryonic physics depends on the properties of dark matter and in particular in warm-dark-matter (WDM) models, star formation may follow a completely different scenario, as compared to the cold-dark-matter case. We use the recent measurements by the EDGES collaboration to demonstrate that when taking the above considerations into account, the robust WDM bounds are in fact weaker than those given by the Lyman-$\alpha$ forest method and other structure formation bounds. In particular, we show that resonantly produced 7 keV sterile neutrino dark matter model is consistent with these data. However, a holistic approach to modelling of the WDM universe holds great potential and may in the future make 21-cm data our main tool to learn about dark matter clustering properties.

  • Gravitational waves from the minimal gauged $U(1)_{B-L}$ model

    by: Hasegawa, Taiki
    An additional $U(1)$ gauge interaction is one of promising extensions of the standard model of particle physics. Among others, the $U(1)_{B-L}$ gauge symmetry is particularly interesting because it addresses the origin of Majorana masses of right-handed neutrinos, which naturally leads to tiny light neutrino masses through the seesaw mechanism. We show that, based on the minimal $U(1)_{B-L}$ model, the symmetry breaking of the extra $U(1)$ gauge symmetry with its minimal Higgs sector in the early Universe can exhibit the first-order phase transition and hence generate a large enough amplitude of stochastic gravitational wave radiation which is detectable in future experiments.

  • Lopsided texture compatible with thermal leptogenesis in partially composite Pati--Salam unification

    by: Yang, Masaki J.S.
    In this paper, we consider a lopsided flavor texture compatible with thermal leptogenesis in partially composite Pati--Salam unification. The Davidson--Ibarra bound for the successful thermal leptogenesis can be recast to the Froggatt--Nielsen (FN) charge of the lopsided texture. We found the FN charge $n_{\nu1}$ of the lightest right-handed neutrino $\nu_{R1}$ can not be larger than a upper bound, $n_{\nu1} \lesssim 4.5$. To realize these FN charges, we utilize the partial compositeness. In this picture, the hierarchies of the Yukawa matrices is a consequence of mixing between massless chiral fermions $f$ and heavy vector fermions $F$. That is induced by the linear mixing terms $\lambda^{f} \bar f_{L} F_{R}$ and $\lambda^{f'} \bar F'_{L} f'_{R}$. If the GUT breaking Higgs contributes these linear mixing terms, the resulting Yukawa interactions can be different between quarks and leptons. For this purpose, we use the bi-fundamental Higgs $H_{R}$ (4,1,2) under the PS group $G_{PS} = SU(4)_{c} \times SU(2)_{L} \times SU(2)_{R}$. A particular set of non-renormalizable couplings between this GUT Higgs and fermions generates GUT breaking linear mixing. As a result, the large $\tan \beta$ case $n_{\nu i} = (1,0,0)$ in which leptons receive mass term seems to be natural. Moreover, it is found that heavy (composite) neutrino sector should have (almost) same flavor structure to reproduce the large mixing of neutrinos by the seesaw formula. If the VEV of GUT breaking Higgs mediates some flavor structure, they contribute to some mass term. Then, this statement can be hold for even in other Pati--Salam model, that does not assume the partial compositeness.

  • Sub-GeV Atmospheric Neutrinos and CP-Violation in DUNE

    by: Kelly, Kevin James (Fermilab) et al.

    We propose to use the unique event topology and reconstruction capabilities of liquid argon time projection chambers to study sub-GeV atmospheric neutrinos. The detection of low energy recoiled protons in DUNE allows for a determination of the leptonic $CP$-violating phase independent from the accelerator neutrino measurement. Our findings indicate that this analysis can exclude several values of $\delta_{CP}$ beyond the $3\sigma$ level. Moreover, the determination of the sub-GeV atmospheric neutrino flux will have important consequences in the detection of diffuse supernova neutrinos and in dark matter experiments.

  • Apparent CPT Violation in Neutrino Oscillation from Dark Non-Standard Interactions

    by: Ge, Shao-Feng
    A natural realization of CPT violation in neutrino oscillation can arise due to the coupling to a light scalar or vector dark matter (DM). The dark non-standard interaction (NSI) is associated with the $\gamma_0$ matrix in neutrino's effective propagator and hence corrects the neutrino Hamiltonian as dark matter potential, in the same way as the ordinary matter effect. The effect is, however, inversely proportional to the neutrino energy and hence appears as a correction to the neutrino mass squared. Due to a sign difference in the corrections for neutrino and anti-neutrino modes, the neutrino oscillation receives CPT violation from the dark NSI. Seeing difference in the neutrino and anti-neutrino mass squared differences not necessarily leads to the conclusion of CPT symmetry breaking in the fundamental Lagrangian but can indicate light DM and its coupling with neutrinos.

  • Phenomenological Study of Texture Zeros in Lepton Mass Matrices of Minimal Left-Right Symmetric Model

    by: Borgohain, Happy
    We consider the possibility of texture zeros in lepton mass matrices of minimal left-right symmetric model (LRSM) where light neutrino mass arises from a combination of type I and type II seesaw mechanisms. Based on the allowed texture zeros in light neutrino mass matrix from neutrino and cosmology data, we make a list of all possible allowed and disallowed texture zeros in Dirac and heavy neutrino mass matrices which appear in type I and type II seesaw terms of LRSM. For the numerical analysis we consider those cases with maximum possible texture zeros in light neutrino mass matrix $M_{\nu}$, Dirac neutrino mass matrix $M_D$, heavy neutrino mass matrix $M_{RR}$ while keeping the determinant of $M_{RR}$ non-vanishing, in order to use the standard type I seesaw formula. The possibility of maximum zeros reduces the free parameters of the model making it more predictive. We then compute the new physics contributions to rare decay processes like neutrinoless double beta decay, charged lepton flavour violation. We find that even for a conservative lower limit on left-right symmetry scale corresponding to heavy charged gauge boson mass 4.5 TeV, in agreement with collider bounds, for right handed neutrino masses above 1 GeV, the new physics contributions to these rare decay processes can saturate the corresponding experimental bound.

  • The NP right-chiral $CC$ coupling constant estimation in neutrino oscillation experiments

    by: Syska, Jacek
    The error probability of the discrimination of the Standard Model (SM) with massive neutrinos and its new physics (NP) model extension in experiments of the muon neutrino oscillation, following the pion decay $\pi^{+} \rightarrow \mu^{+} + \nu_{\mu}$, is calculated. The stability of the estimation of the NP charged current coupling constant $\varepsilon_{R}$ is analysed and the robustness of this estimation is checked.

  • Short-baseline neutrino oscillations with 3+1 non-unitary mixing

    by: Giunti, C.
    We consider a scenario with unitary mixing of the three light standard neutrinos and a non-unitary mixing contribution of a heavier massive neutrino that can generate short-baseline neutrino oscillations. We show that this scenario predicts constant flavor-changing probabilities at short-baseline distances. Therefore, it cannot explain the spectral distortions observed in the LSND and MiniBooNE appearance experiments. On the other hand, the survival probabilities oscillate as functions of $L/E$ and could explain oscillations in short-baseline disappearance experiments. We also derive the bounds on the mixing parameters from the existing short-baseline neutrino oscillation data.

  • CP-Violation phase analysis via non-trivial correlation of quarks and leptons in 3+1 scenario

    by: Sharma, Gazal
    The existence and mysterious nature of sterile neutrinos are revolutionizing physics from the particle level to the cosmological scales. The recent results from the MiniBooNE experiment at Fermi-lab observed far more $\nu_{e}$ appearance than expected, which have provided a hint about the possible existence of \textit{sterile neutrinos}. The results, if confirmed in future experiments, will have significant implications for cosmology and astroparticle physics. This will require new neutrino mass models to accommodate these additional degrees of freedom. In respect to that, the present work is just an extension of our recent work towards the CP phase analysis of Quark-lepton complementarity(QLC) model in a 3+1 scenario. The parametrization of $CKM_{4}$ and $PMNS_{4}$ using Monte Carlo Simulation is used to estimate the texture of non-trivial correlation matrix ($V_{c_{4}}$). As such, we have successfully investigated the constrained values for sterile neutrino parameters, and also predicted the values for Dirac CP-Violation phase and the CP re-phasing invariant (J). The results obtained are consistent with the data available from various experiments, like No$\nu$A, MINOS, SuperK and IceCube-DeepCore. Furthermore, this analysis would be very important in view of growing sterile neutrino experiments.

  • Pushing the Energy and Cosmic Frontiers with High-Energy Astrophysical Neutrinos

    by: Bustamante, Mauricio
    The astrophysical neutrinos recently discovered by the IceCube neutrino telescope have the highest detected neutrino energies --- from TeV to PeV --- and travel the longest distances --- up to a few Gpc, the size of the observable Universe. These features make them naturally attractive probes of fundamental particle-physics properties, possibly tiny in size, at energy scales unreachable by any other means. The decades before the IceCube discovery saw many proposals of particle-physics studies in this direction. Today, those proposals have become a reality, in spite of prevalent astrophysical unknowns. We showcase examples of studying fundamental neutrino physics at these scales, including some of the most stringent tests of physics beyond the Standard Model.

  • Seeking for sterile neutrinos with displaced leptons at the LHC

    by: Liu, Jia
    We study the signal of long-lived sterile neutrino at the LHC produced through the decay of the $W$ boson. It decays into charged lepton and jets. The characteristic signature is a hard prompt lepton and a lepton from the displaced decay of the sterile neutrino, which leads to a bundle of displaced tracks with large transverse impact parameter. Different from other studies, we neither reconstruct the displaced vertex nor place requirement on its invariant mass to maintain sensitivity for low sterile neutrino masses. Instead, we focus on the displaced track from the lepton. A difficulty for low mass sterile neutrino study is that the displaced lepton is usually \textit{non-isolated}. Therefore, leptons from heavy flavor quark is the major source of background. We closely follow a search for displaced electron plus muon search at CMS and study their control regions, which is related to our signal regions, in great detail to develop a robust estimation of the background for our signals. After further optimization on the signal limiting the number of jets, low $H_T$ and large lepton displacement $d_0$ to suppress SM background, we reach an exclusion sensitivity of about $10^{-8}$ ($10^{-5}$) for the mixing angle square at 10 (2) GeV sterile neutrino mass respectively. The strategy we propose can cover the light sterile masses complimentary to beam dump and forward detector experiments.

  • Probing Sterile Neutrino via Lepton Flavor Violating Decays of Mesons

    by: Hu, Shiyong (Jinan U.) et al.

    A sterile neutrino at GeV mass scale is of particular interest in this work. Though not take part in neutrino oscillation, the sterile neutrino can induce flavor violating semileptonic and leptonic decay of $K, D$ and $B$ mesons. We calculated a box diagram contribution in these processes. By making use of current experiment limit of lepton flavor violating decays $M^+_h\to M_l^+\ell_1^+\ell_2^-$ and $M^0\to \ell_1^-\ell_2^+$, we explore the allowed parameter space of $U_{e4}$ and $U_{\mu 4}$ in different mass ranges. Generally speaking, both channels give a limit to the product of $U_{e4}$ and $U_{\mu 4}$. When sterile neutrino mass is located in between pion and kaon mass, $K^+\to \pi^+ e^{\pm}\mu^{\mp}$ gives the strongest constraint while $B^+\to \pi^+ e^{\pm} \mu^{\mp}$ provides the dominated constraint when its mass in between of kaon and B meson. If sterile neutrino is even heavier than B mesons, the $B^0_s\to \mu^{\pm} e^{\mp}$ experiment which is performed at LHCb gives the strongest constraint.

  • Proton decay at 1-loop

    by: Helo, Juan Carlos (La Serena U.) et al.

    Proton decay is usually discussed in the context of grand unified theories. However, as is well-known, in the standard model effective theory proton decay appears in the form of higher dimensional non-renormalizable operators. Here, we study systematically the 1-loop decomposition of the $d=6$ $B+L$ violating operators. We exhaustively list the possible 1-loop ultra-violet completions of these operators and discuss that, in general, two distinct classes of models appear. Models in the first class need an additional symmetry in order to avoid tree-level proton decay. These models necessarily contain a neutral particle, which could act as a dark matter candidate. For models in the second class the loop contribution dominates automatically over the tree-level proton decay, without the need for additional symmetries. We also discuss possible phenomenology of two example models, one from each class, and their possible connections to neutrino masses, LHC searches and dark matter.

  • Neutrino Mass and Mixing with $A_5$ Modular Symmetry

    by: Ding, Gui-Jun (Hefei, CUST) et al.

    We present a comprehensive analysis of neutrino mass and lepton mixing in theories with $A_5$ modular symmetry. We construct the weight 2, weight 4 and weight 6 modular forms of level 5 in terms of Dedekind eta-functions and Klein forms, and their decomposition into irreducible representation of $A_5$. We construct all the simplest models based on $A_5$ modular symmetry, including scenarios of models with and without flavons in the charged lepton sectors. For each case, the neutrino masses can be generated through either the Weinberg operator or the type I seesaw mechanism. We perform an exhaustive numerical analysis, organising our results in an extensive set of figures and tables.

  • KeV scale new fermion from a hidden sector

    by: Chang, We-Fu (Taiwan, Natl. Tsing Hua U.) et al.

    We studied a simple model of hidden sector consists of a Dirac fermion $\chi$ and a spontaneously broken $U(1)_s$ symmetry. The dark sector is connected to the Standard Model(SM) via three righthanded SM singlet neutrinos, $N_R$'s, and the kinetic mixing between $U(1)_s$ and $U(1)_Y$. A mixing between the scalar $\phi$ that breaks $U(1)_s$ and the SM Higgs boson, $H$, is implemented via the term $\phi^\dagger \phi H^\dagger H$ and this provides a third connection to the SM. Integrating out the $N_R$ at a high scale not only gives the active neutrinos, $\nu$, masses but generates effective Dirac type of couplings between $\nu$ and $\chi$. This changes the usual Type-I seesaw results for active neutrino masses and makes $\chi$ behave like a sterile neutrino even though its origin is in the hidden sector. $\chi$ is also split into a pair of Majorana fermions. The amount of splitting depends on the parameters. If the lighter of the pair has a mass around keV, its lifetime is longer than the age of the universe and it can be a warm dark matter candidate. Signatures of $\chi$ in high precision Kurie plots of nuclei $\beta$ decays and low energy neutrino nuclei coherent scatterings are discussed. The model also induces new invisible $Z$ decay modes that can be searched for in future Z factories.

  • Radiative Dirac Neutrino Mass with Dark Matter and it's implication to $0\nu 4\beta$ in the $U(1)_{B-L}$ extension of the Standard Model

    by: Dasgupta, Arnab (Seoultech) et al.

    The Standard Model gauge symmetry is extended by $U(1)_{B-L}$ which when spontaneously broken leads to residual $\mathbb{Z}_4$ symmetry. $U(1)_{B-L}$ gauge symmetry made anomaly free by introducing exotic SM singlets with corresponding $U(1)_{B-L}$ charges of $13$, $-14$, and $15$. $\mathbb{Z}_4$ symmetry ensures the Dirac nature of neutrinos, simultaneously stabilizing dark matter. Dirac neutrino mass is generated through scotogenic scenario. Dark matter, direct detection, cosmological constraints, and collider constraints analysis is performed. $\mathbb{Z}_4$ symmetry predicts the exact absence of neutrinoless double beta decay ($0\nu 2\beta$) and gives a prediction for an enhanced neutrinoless quadruple beta decay ($0\nu 4\beta$) via which this model can be tested. Model allows for Majorana dark matter as well as for long-lived dark matter candidates.

  • Perturbative unitarity bounds for effective composite models

    by: Biondini, S. (Groningen U.) et al.

    In this paper we present the partial wave unitarity bound in the parameter space of dimension-5 and dimension-6 effective operators that arise in a compositeness scenario. These are routinely used in experimental searches at the LHC to constraint contact and gauge interactions between ordinary Standard Model fermions and excited (composite) states of mass $M$. After deducing the unitarity bound for the production process of a composite neutrino, we implement such bound and compare it with the recent experimental exclusion curves for Run 2, the High-Luminosity and High-Energy configurations of the LHC. Our results also applies to the searches where a generic single excited state is produced via contact interactions. We find that the unitarity bound, so far overlooked, is quite complelling and significant portions of the parameter space ($M,\Lambda$) become excluded in addition to the standard request $M \le \Lambda$.

  • Mirror Dirac leptogenesis

    by: Earl, Kevin (Ottawa Carleton Inst. Phys.) et al.

    We consider a novel scenario, based on the existence of a mirror world, in which light Dirac neutrinos are generated from a seesaw mechanism and leptogenesis occurs at high scale without violating lepton number. Since lepton number is conserved, this model predicts no neutrinoless double beta decay. After leptogenesis, the conservation law of the theory implies the visible baryon-minus-lepton asymmetry to be equal to the mirror baryon-minus-lepton asymmetry. The final baryon and mirror baryon asymmetries, however, will be related by an order one coefficient, which depends on the details of the model. If dark matter consists of mirror baryons, this can naturally explain the proximity of baryon and dark matter energy densities.

  • Neutrino mass via linear seesaw, 331-model and Froggatt-Nielsen mechanism

    by: Huitu, Katri (Helsinki U.) et al.

    In this paper, we introduce an extension of the Standard Model, based on SU(3)$_\mathrm{C}\times $SU(3)$_\mathrm{L}\times $U(1)$_X$ gauge symmetry (331-model). The 331-models traditionally explain the number of fermion familes in nature. In our model the Froggatt-Nielsen mechanism is incorporated into the 331-setting in a particularly economical fashion. The model utilizes the both the Froggatt-Nielsen and linear seesaw mechanisms to explain the observed fermion mass hierarchies and lightness of neutrinos. In our numerical analysis we found that a $\sim$ 50 TeV new physics scale is able to reproduce correctly all the fermion masses and mixing matrices, including neutrino masses, mass squared differences and mixing matrix.

  • BSM Matter providing Neutrino Masses and Gauge Unification

    by: Picek, Ivica (Zagreb U., Phys. Dept.)

    I present several scenarios developed in Zagreb, in which TeV-scale particles belonging to non-trivial weak-isospin multiplets give rise to neutrino-mass mechanisms different from conventional type I, II and III seesaw models. Two dim 9 tree-level mechanisms, presented first, provide an appealing testability of their exotic TeV-scale particles at the LHC. These models are not genuine, since their particles also provide competing dim 5 loop contributions. The loop-models presented next are genuine, without competing tree-level contributions. Among them, the three-loop model involves high-order weak multiplets leading to Landau poles. The one-loop model with scalar triplet as the largest multiplet, in addition to good UV properties, provides the particle set promising for gauge coupling unification. Therefore, it served us as a starting point for a study of SU(5) embedding of additional particles leading to viable unification scenarios. To distinguish among them begs for additional principle which reigns over particle completion and eventual dark matter considerations.

  • Measuring the Neutron Distribution from Coherent Elastic Neutrino Nucleus Scattering

    by: Ciuffoli, Emilio (Lanzhou, Inst. Modern Phys.)

    Last year the COHERENT collaboration was able to measure for the first time the Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS). Neutrinos within the right energy range can be produced in large quantities at accelerator facilities via pion Decay At Rest ($\pi$DAR) and used to measure CE$\nu$NS. This new channel opens several, interesting possibilities: studying the CE$\nu$NS spectrum it will be possible, for example, to search for Physics Beyond the Standard Model, looking for deviations from the predictions of the electroweak theory; it can also give important inputs for the understanding of core collapse supernovas, where neutrino-nucleus interactions and, more generally, collective neutrino behavior play a crucial role. Using CE$\nu$NS it is also possible to measure precisely the electroweak form factor for a large number of different nuclei, extracting information on the neutron distribution inside the nucleus as well. In this presentation I will focus on the last aspect: I will calculated the precision that can be achieved in such kind of experiment, investigating in particular the effects of the low-energy threshold and the systematic errors on the quenching factor. The expected precision will be calculated using the Helm model and also with a model-independent approach.

  • Probing new physics with displaced vertices: muon tracker at CMS

    by: Bondarenko, Kyrylo (Leiden U.) et al.

    Long-lived particles can manifest themselves at the LHC via "displaced vertices" - several charged tracks originating from a position separated from the proton interaction point by a macroscopic distance. Here we demonstrate a potential of the muon trackers at the CMS experiment for displaced vertex searches. We use heavy neutral leptons and Chern-Simons portal as two examples of long-lived particles for which the CMS muon tracker can provide essential information about their properties.

  • Neutrinos and gamma rays from long-lived mediator decays in the Sun

    by: Niblaeus, Carl (Stockholm U., OKC) et al.

    We investigate a scenario where dark matter (DM) particles can be captured and accumulate in the Sun, and subsequently annihilate into a pair of long-lived mediators. These mediators can decay further out in the Sun or outside of the Sun. Compared to the standard scenario where DM particles annihilate directly into Standard Model particles close to the solar core, here we also obtain fluxes of gamma rays and charged cosmic rays. We simulate this scenario using a full three-dimensional model of the Sun, and include interactions and neutrino oscillations. In particular, we perform a model-independent study of the complementarity between neutrino and gamma ray fluxes by comparing the recent searches from IceCube, Super-Kamiokande, Fermi-LAT, ARGO and HAWC. We find that the resulting neutrino fluxes are significantly higher at high energy when the mediators decay further out in the Sun. We also find that gamma ray searches place stronger constraints than neutrino searches on these models even in cases where the mediators decay mainly inside the Sun, except in the approximately inner 10% of the Sun where neutrino searches are more powerful. We present our results in a model-independent manner and release a new version of the WimpSim code that can be used to simulate this scenario for arbitrary mediator models.

  • $R_K$ and $R_{K^*}$ in an Aligned 2HDM with Right-Handed Neutrinos

    by: Delle Rose, Luigi (Florence U.) et al.

    We consider the possibility to explain the recent $R_K$ and $R_{K ^*}$ anomalies in a 2-Higgs Doublet Model, known as Aligned, combined with a low scale seesaw mechanism generating light neutrino masses and mixings. In this class of models, a large Yukawa coupling allows for significant non-universal leptonic contributions, through box diagrams mediated by charged Higgs bosons and right-handed neutrinos, to the $b \to s \ell^+ \ell^-$ transition that can then account for both $R_K$ and $R_{K^*}$ anomalies.

  • Searching for Beyond the Standard Model Physics with COHERENT Energy and Timing Data

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

    We study the prospects for extracting information on beyond the Standard Model (BSM) physics by combining the energy and timing distribution of nuclear recoil events in the COHERENT neutrino-nucleus elastic scattering data. Focusing on light, $\lesssim$ GeV mediators as an example, we find that the combined energy and timing data favor a $\sim 10-1000$ MeV mediator as compared to the Standard Model (SM) best fit at the $\lesssim 2\sigma$ level. The timing data provides additional statistical information on the electron and muon neutrino flavor distributions that is not attainable from the energy distribution of nuclear recoils alone. This result accounts for the uncertainty in the effective size of the neutron distribution, and highlights the power of an analysis which includes uncertainties on the experimental backgrounds, the nuclear model, the BSM parameters, and uses the full energy and timing information.

  • Model-independent upper limits on lepton number violating states from neutrino mass
    SISSA 07/2019/FISI

    by: Herrero-García, Juan (SISSA, Trieste) et al.

    We propose a model-independent framework to classify and study neutrino mass models and their phenomenology. The idea is to introduce one particle beyond the Standard Model which couples to leptons and carries lepton number together with the lowest-dimensional operator which violates lepton number by two units and contains this particle. The resulting contribution to neutrino masses can be translated to a robust upper bound on the mass of the new particle. We compare it to the stronger but less robust upper bounds from Higgs naturalness and discuss several lower bounds.

  • Two-component Dark Matter with co-genesis of Baryon Asymmetry of the Universe

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

    We discuss the possibility of realising a two-component dark matter (DM) scenario where the two DM candidates differ from each other by virtue of their production mechanism in the early universe. One of the DM candidates is thermally generated in a way similar to the weakly interacting massive particle (WIMP) paradigm where the DM abundance is governed by its freeze-out while the other candidate is produced only from non-thermal contributions similar to freeze-in mechanism. We discuss this in a minimal extension of the standard model where light neutrino masses arise radiatively in a way similar to the scotogenic models with DM particles going inside the loop. The lepton asymmetry is generated at the same time from WIMP DM annihilations as well as partially from the mother particle for non-thermal DM. This can be achieved while satisfying the relevant experimental bounds, and keeping the scale of leptogenesis or the thermal DM mass as low as 3 TeV, well within present experimental reach. In contrast to the TeV scale thermal DM mass, the non-thermal DM can be as low as a few keV, giving rise to the possibility of a sub-dominant warm dark matter (WDM) component that can have interesting consequences on structure formation. The model also has tantalizing prospects of being detected at ongoing direct detection experiments as well as the ones looking for charged lepton flavour violating process like $\mu \rightarrow e \gamma$.

  • Effective alignments and the landscape of $S_4$ flavour models

    by: De Medeiros Varzielas, Ivo (Lisbon, CFTP) et al.

    We explore the concept of effective alignments: contractions of multiple flavour symmetry breaking flavon fields. These contractions give rise to directions that are hard or impossible to obtain directly by breaking the flavour symmetry. Within this context, and using $S_4$ as the flavour symmetry to exemplify, we perform a phenomenological check of lepton flavour models built from pairing any two effective alignments up to order 2 (in flavon contractions). The check is performed for each pair of effective alignments in a framework with models of constrained sequential dominance type, in a basis where the charged leptons are diagonal. We thus obtain an indication of which effective alignments are interesting for model building, within this so-called $S_4$ landscape. We find three types of viable topologies and provide examples of models realizing this strategy for each topology.

  • Hunting On- and Off-Axis for Light Dark Matter with DUNE-PRISM

    by: De Romeri, Valentina (Valencia U., IFIC) et al.

    We present the prospects for exploring low-scale dark sectors with the future DUNE experiment and the impact of the movable off-axis near detector concept, DUNE-PRISM, and a higher energy beam configuration. We focus on a simple scenario which extends the Standard Model by a "dark" $U(1)_D$, comprised of scalar or fermion dark matter and a dark photon kinetically mixed with the photon. We consider nucleus and electron scattering signatures of dark matter produced in the beam via neutral pseudoscalar meson decays. Our results show that, by analyzing the energy spectra of single-electron events in multiple off-axis angle, DUNE-PRISM can substantially increase the experimental sensitivity to these models, reaching theoretical targets for thermal relic dark matter for a wide range of dark photon and dark matter masses.

  • On explaining the observed pattern of quark and lepton masses

    by: Hosek, Jiri (Rez, Nucl. Phys. Inst.)

    Higgs sector of the Standard model (SM) is replaced by the gauge $SU(3)_f$ quantum flavor dynamics (QFD) with one parameter, the scale $\Lambda$. Anomaly freedom of QFD demands extension of the fermion sector of SM by three sterile right-handed neutrino fields. Poles of fermion propagators with chirality-changing self-energies $\Sigma(p^2)$ spontaneously generated by QFD at strong coupling define: (1) Three sterile-neutrino Majorana masses $M_{fR}$ of order $\Lambda$. (2) Three Dirac masses $m_f$, degenerate for $e_f, \nu_f, u_f, d_f$ in family $f$, exponentially small with respect to $\Lambda$. Goldstone theorem implies: All eight flavor gluons acquire masses of order $M_{fR}$. $W$ and $Z$ bosons acquire masses of order $\sum m_f$, the effective Fermi scale. Composite 'would-be' Nambu-Goldstone bosons have their 'genuine' partners, the composite Higgs particles: The SM-like Higgs $h$ and two new Higgses $h_3$ and $h_8$, all with masses at Fermi scale; three Higgses $\chi_i$ with masses at scale $\Lambda$. Large pole-mass splitting of charged leptons and quarks in $f$ is arguably due to full QED $\Sigma(p^2)$-dependent fermion-photon vertices enforced by Ward-Takahashi identities. The argument relies on illustrative computation of pole-mass splitting found non-analytic in fermion electric charges. Neutrinos are the Majorana particles with seesaw mass spectrum computed solely by QFD. Available data fix $\Lambda$ to, say, $\Lambda \sim 10^{14} \rm GeV$.

  • $b\to s\ell^+\ell^-$ Transitions in Two-Higgs-Doublet Models
    ZU-TH 10/19

    by: Crivellin, Andreas (PSI, Villigen) et al.

    In this article we study $b\to s\mu^+\mu^-$ transitions and possible correlations with the anomalous magnetic moment of the muon ($a_\mu$) within two-Higgs-doublet models with generic Yukawa couplings, including the possibility of right-handed neutrinos. We perform the matching on the relevant effective Hamiltonian and calculate the leading one-loop effects for $b\to s\ell\ell^{(\prime)}$, $b\to s\gamma$, $\Delta B=\Delta S=2$, $b\to s\nu\bar\nu$ and $\ell\to\ell^\prime\gamma$ transitions in a general $R_\xi$ gauge. Concerning the phenomenology, we find that an explanation of the hints for new physics in $b\to s\mu^+\mu^-$ data is possible once right-handed neutrinos are included. If lepton flavour violating couplings are allowed, one can account for the discrepancy in $a_\mu$ as well. However, only a small portion of parameter space gives a good fit to $b\to s\mu^+\mu^-$ data and the current bound on $h\to\tau\mu$ requires the mixing between the neutral Higgses to be very small if one aims at an explanation of $a_\mu$.

  • Exploring new physics from $\nu_\tau$ events in OPERA
    Phys.Lett. B792 (2019) 199-204

    by: Meloni, Davide (Rome III U.)

    We analyze in details the impact of the $10$ $\nu_\tau$ events seen in the OPERA experiment in constraining the Non Standard Interaction parameter $\varepsilon_{\mu\tau}$ affecting neutrino propagation in matter and the allowed parameter space of models with one sterile neutrino of the $3+1$ type.

  • Inflation meets neutrinos
    Phys.Rev. D99 (2019) 083515

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

    Constraints on inflationary models typically assume only the standard models of cosmology and particle physics. By extending the neutrino sector to include a new interaction with a light scalar mediator ($m_{\phi}\sim$MeV), it is possible to relax these constraints, in particular via opening up regions of the parameter space of the spectral index $n_s$. These new interactions can be probed at IceCube via interactions of astrophysical neutrinos with the Cosmic Neutrino Background for nearly all of the relevant parameter space.

  • Mean field and two-body nuclear effects in inclusive electron scattering on argon, carbon and titanium: the superscaling approach
    Phys.Rev. C99 042501
    Phys.Rev. C99 (2019) 042501

    by: Barbaro, M.B. (INFN, Turin) et al.

    We compare the predictions of the SuSAv2 model including two-particle two-hole meson-exchange currents with the recent JLab data for inclusive electron scattering on three different targets (C, Ar and Ti). The agreement is very good over the full energy spectrum, with some discrepancy seen only in the deep inelastic region. The 2p2h response, peaked in the dip region between the quasielastic and $\Delta$-resonance peak, is essential to reproduce the data. We also analyze the $k_F$ (Fermi momentum) dependence of the data in terms of scaling of second kind, showing that the 2p2h response scales very differently from the quasielastic one, in full accord with what is predicted by the model. The results represent a valuable test of the applicability of the model to neutrino scattering processes on different nuclei.

  • New mixing schemes for (3+1) neutrinos
    Nucl.Phys. B941 (2019) 401-424

    by: Dev, S. (HNB Garhwal U.) et al.

    We propose new mixing schemes for (3+1) neutrinos which describe mixing among active-active and active-sterile neutrinos. The mixing matrix in these mixing schemes can be factored into a zeroth order flavor symmetric part and another part representing small perturbations needed for generating non-zero Ue3 , nonmaximal θ23 , CP violation and active-sterile mixing. We find interesting correlations amongst various neutrino mixing angles and, also, calculate the parameter space for various parameters.

  • Neutrino oscillation probabilities through the looking glass
    Phys.Lett. B791 (2019) 351-360

    by: Barenboim, Gabriela (Brookhaven) et al.

    In this paper we review different expansions for neutrino oscillation probabilities in matter in the context of long-baseline neutrino experiments. We examine the accuracy and computational efficiency of different exact and approximate expressions. We find that many of the expressions used in the literature are not precise enough for the next generation of long-baseline experiments, but several of them are while maintaining comparable simplicity. The results of this paper can be used as guidance to both phenomenologists and experimentalists when implementing the various oscillation expressions into their analysis tools.

  • Seesaw mirroring between light and heavy Majorana neutrinos with the help of the S$_{3}$ reflection symmetry
    JHEP 1903 (2019) 184

    by: Xing, Zhi-Zhong (Beijing, GUCAS) et al.

    In the canonical seesaw mechanism we require the relevant neutrino mass terms to be invariant under the $S^{}_3$ charge-conjugation transformations of left- and right-handed neutrino fields. Then both the Dirac mass matrix $M^{}_{\rm D}$ and the right-handed neutrino mass matrix $M^{}_{\rm R}$ are well constrained, so is the effective light Majorana neutrino mass matrix $M^{}_\nu$ via the seesaw formula. We find that these mass matrices can be classified into 22 categories, among which some textures respect the well-known $\mu$-$\tau$ permutation or reflection symmetry and flavor democracy. It is also found that there exist remarkable structural equalities or similarities between $M^{}_\nu$ and $M^{}_{\rm R}$, reflecting a seesaw mirroring relationship between light and heavy Majorana neutrinos. We calculate the corresponding light neutrino masses and flavor mixing parameters as well as the CP-violating asymmetries in decays of the lightest heavy Majorana neutrino, and show that only the flavored leptogenesis mechanism is possible to work for three categories of $M^{}_{\rm D}$ and $M^{}_{\rm R}$ in the $S^{}_3$ reflection symmetry limit.

  • The SU(8) GUT with composite quarks and leptons
    Nucl.Phys. B941 (2019) 425-457

    by: Chkareuli, J.L. (Ilia State U.)

    We consider the $L$-$R$ symmetric composite model for quarks and leptons where constituent preons possessing some local $SU(N)_{MF}$ metaflavor symmetry are bound by the chiral $SO(n)_{L}\times SO(n)_{R}$ gauge metacolor forces. The strengthening of the 't Hooft's anomaly matching condition, when the massless fermion composites are required to complete a single representation of the $SU(N)_{MF}$ rather than some set of its representations, allows to fix the number of basic metaflavors $N$. Particularly, just eight left-handed and eight right-handed preons and their composites preserving the global chiral symmetry $SU(8)_{L}\times SU(8)_{R}$ are turned out to underlie the physical world at small distances that uniquely identifies the local metaflavor symmetry $SU(8)_{MF}$ as its effective unified symmetry. We next show that the spontaneous $L$-$R$ symmetry violation caused by composite scalars reduces this initially vectorlike $SU(8)_{MF}$ theory down to the conventional $SU(5)$ GUT with an extra local family symmetry $SU(3)_{F}$ and three standard families of quarks and leptons. Though the tiny confinement scale for universal preons composing both quarks and leptons makes it impossible to directly confirm their composite nature, simultaneous emergence of several extra $SU(5)\times SU(3)_{F}$ multiplets of heavy composite fermions may help with a model verification. Generally, they may be located at scales from $O(100)$ $TeV$ up to the Planck mass scale depending on an interplay between the compositeness scale and scale of the family symmetry $SU(3)_{F}$. Some of them through a natural see-saw mechanism provide neutrino masses which, in contrast to conventional picture, appear to follow an inverted family hierarchy. Others mix with ordinary quark-lepton families in a way that there may arise a marked violation of unitarity in the CKM matrix for leptons.

  • Sign of CP Violating Phase in Quarks and Leptons
    JHEP 1904 (2019) 074

    by: Shimizu, Yusuke (Hiroshima U.) et al.

    We discuss the relation between the CP violation of the quark mixing and that of the lepton mixing by investigating a CP violating observable, the Jarlskog invariant, as well as the CP violating Dirac phase. The down-type quark mass matrix with three zeros is given in terms of the minimal number of parameters, while the up-type quark mass matrix is diagonal. These quark mass matrices leading to the successful CKM mixing angles and CP violation are embedded in both the Pati--Salam and SU(5) models. The leptonic Jarlskog invariant $J_{CP}^l$ (as well as CP violating Dirac phase) is examined for two cases: the neutrino mass matrix is diagonal or non-diagonal, where no additional CP violating phase is introduced apart from the Majorana phases. In the case of the diagonal neutrino mass matrix, the favorable sign of the leptonic CP violation is obtained, however, the magnitude of $J_{CP}^l$ is at most ${\cal O}(10^{-4})$, which is too small compared with the expected value from the observation $-0.02$. In the case of the non-diagonal neutrino mass matrix where the tri-bimaximal mixing pattern is taken, we obtain the successful $J_{CP}^l$ up to its sign.

  • Tensor and scalar interactions of neutrinos may lead to observable neutrino magnetic moments
    Phys.Rev. D99 (2019) 075003

    by: Xu, Xun-Jie (Heidelberg, Max Planck Inst.)

    Recently more generalized four-fermion interactions of neutrinos such as tensor and scalar interactions (TSIs) have been extensively studied in response to forthcoming precision measurements of neutrino interactions. We show that due to the chirality-flipping nature, at the one-loop level TSIs typically generate much larger (107–1010) neutrino magnetic moments (νMMs) than the vector case. For some cases, the large νMMs generated by TSIs may reach the known bounds, which implies potentially important interplay between probing TSIs and searching for νMMs in current and future neutrino experiments.

  • Leptonic CP violation in flipped SU(5) GUT from $Z_{12−I}$ orbifold compactification
    Phys.Lett. B791 (2019) 215-224

    by: Jeong, Junu (IBS, Daejeon) et al.

    We obtain a phenomenologically acceptable PMNS matrix in a flipped SU(5) model inspired by the compactification of heterotic string $E_8\times E_8'$. To analyze the Jarlskog determinant efficiently, we include the simple Kim-Seo form for the Pontecorbo-Maki-Nakagawa-Sakata matrix. We also noted that $|\delta_{\rm PMNS}|\lesssim 64^{\rm o}$ for the normal hierarchy of neutrino masses with the PDG book parametrization.

  • New Constraints on Sterile Neutrino Dark Matter from $NuSTAR$ M31 Observations
    Phys.Rev. D99 (2019) 083005

    by: Ng, Kenny C.Y. (Weizmann Inst.) et al.

    We use a combined 1.2 Ms of $NuSTAR$ observations of M31 to search for X-ray lines from sterile neutrino dark matter decay. For the first time in a $NuSTAR$ analysis, we consistently take into account the signal contribution from both the focused and unfocused fields of view. We also reduce the modeling systematic uncertainty by performing spectral fits to each observation individually and statistically combining the results, instead of stacking the spectra. We find no evidence of unknown lines, and thus derive limits on the sterile neutrino parameters. Our results place stringent constraints for dark matter masses $\gtrsim 12$ keV, which reduces the available parameter space for sterile neutrino dark matter produced via neutrino mixing ($e.g.$, in the $\nu$MSM) by approximately one-third. Additional $NuSTAR$ observations, together with improved low-energy background modeling, could probe the remaining parameter space in the future. Lastly, we also report model-independent limits on generic dark matter decay rates and annihilation cross sections.

  • Diagnosing the Reactor Antineutrino Anomaly with Global Antineutrino Flux Data
    Phys.Rev. D99 (2019) 073005

    by: Giunti, C. (INFN, Turin) et al.

    We have examined the impact of new Daya Bay, Double Chooz, and RENO measurements on global fits of reactor antineutrino flux data to a variety of hypotheses regarding the origin of the reactor antineutrino anomaly. In comparing RENO and Daya Bay measurements of inverse beta decay (IBD) yield versus $^{239}$Pu fission fraction, we find differing levels of precision in measurements of time-integrated yield and yield slope, but similar central values, leading to modestly enhanced isotopic IBD yield measurements in a joint fit of the two datasets. In the absence of sterile neutrino oscillations, global fits to all measurements now provide 3{\sigma} preference for incorrect modeling of specific fission isotopes over common mis-modeling of all beta-converted isotopes. If sterile neutrino oscillations are considered, global IBD yield fits provide no substantial preference between oscillation-including and oscillation-excluding hypotheses: hybrid models containing both sterile neutrino oscillations and incorrect $^{235}$U or $^{239}$Pu flux predictions are favored at only 1-2{\sigma} with respect to models where $^{235}$U, $^{238}$U, and $^{239}$Pu are assumed to be incorrectly predicted.

  • Mononeutrino at DUNE: New signals from neutrinophilic thermal dark matter
    Phys.Rev. D99 (2019) 055034

    by: Kelly, Kevin J. (Fermilab) et al.

    We introduce the mono-neutrino signal at neutrino detectors as a smoking gun of sub-GeV scale dark matter candidates that mainly interact with standard model neutrinos. In a mono-neutrino process, invisible particles, either dark matter themselves or the mediator particle, are radiated off a neutrino when it undergoes the charged-current weak interaction. The associated signals include a missing transverse momentum with respect to the incoming neutrino beam direction and the production of wrong-sign charged leptons. We demonstrate the potential leading role of the future DUNE experiment, using its proposed liquid and gas argon near detectors, in probing these new signals and the thermal origins of neutrinophilic dark matter.

  • Foraging for dark matter in large volume liquid scintillator neutrino detectors with multiscatter events
    Phys.Rev. D99 (2019) 083010

    by: Bramante, Joseph (Queen's U., Kingston) et al.

    We show that dark matter with a per-nucleon scattering cross section $\gtrsim 10^{-28}~{\rm cm^2}$ could be discovered by liquid scintillator neutrino detectors like BOREXINO, SNO+, and JUNO. Due to the large dark matter fluxes admitted, these detectors could find dark matter with masses up to $10^{21}$ GeV, surpassing the mass sensitivity of current direct detection experiments (such as XENON1T and PICO) by over two orders of magnitude. We derive the spin-independent and spin-dependent cross section sensitivity of these detectors using existing selection triggers, and propose an improved trigger program that enhances this sensitivity by two orders of magnitude. We interpret these sensitivities in terms of three dark matter scenarios: (1) effective contact operators for scattering, (2) QCD-charged dark matter, and (3) a recently proposed model of Planck-mass baryon-charged dark matter. We calculate the flux attenuation of dark matter at these detectors due to the earth overburden, taking into account the earth's density profile and elemental composition, and nuclear spins.

  • FCC-he sensitivity estimates on the anomalous electromagnetic dipole moments of the top-quark
    Nucl.Phys. B941 (2019) 646-664

    by: Hernández-Ruíz, M.A. (Zacatecas U.) et al.

    In this paper, we study the production of a top-quark in association with a bottom-quark and a electron-neutrino at the Future Circular Collider Hadron Electron (FCC-he) to probe the sensitivity on its magnetic moment (aˆV) and its electromagnetic dipole moment (aˆA) through the process e−p→e−γp→t¯νebp . Assuming a large amount of collisions, as well as of data with cleaner environments, the FCC-he is an excellent option to study new physics, such as the aˆV and aˆA . For our sensitivity study on aˆV and aˆA , we consider center-of-mass energies s=7.07,10 TeV and luminosities L=50,100,300,500,1000 fb−1 . In addition, we apply systematic uncertainties δsys=0%,3%,5% and we consider unpolarized and polarized electron beam. Our results show that the FCC-he is a very good perspective to probe the aˆV and aˆA at high-energy and high-luminosity frontier.

  • Natural Seesaw and Leptogenesis from Hybrid of High-Scale Type I and TeV-Scale Inverse
    JHEP 1904 (2019) 029

    by: Agashe, Kaustubh (Maryland U.) et al.

    We develop an extension of the basic inverse seesaw model which addresses simultaneously two of its drawbacks, namely, the lack of explanation of the tiny Majorana mass term $\mu$ for the TeV-scale singlet fermions and the difficulty in achieving successful leptogenesis. Firstly, we investigate systematically leptogenesis within the inverse (and the related linear) seesaw models and show that a successful scenario requires either small Yukawa couplings, implying loss of experimental signals, and/or quasi-degeneracy among singlets mass of different generations, suggesting extra structure must be invoked. Then we move to the analysis of our new framework, which we refer to as hybrid seesaw. This combines the TeV degrees of freedom of the inverse seesaw with those of a high-scale ($M_N\gg$ TeV) seesaw module in such a way as to retain the main features of both pictures: naturally small neutrino masses, successful leptogenesis, and accessible experimental signatures. We show how the required structure can arise from a more fundamental theory with a gauge symmetry or from warped extra dimensions/composite Higgs. We provide a detailed derivation of all the analytical formulae necessary to analyze leptogenesis in this new framework, and discuss the entire gamut of possibilities our scenario encompasses: including scenarios with singlet masses in the enlarged range $M_N \sim 10^6 - 10^{16}$ GeV. The idea of hybrid seesaw was proposed by us in arXiv:1804.06847; here, we substantially elaborate upon and extend earlier results

  • Symmetry Breaking and Reheating after Inflation in No-Scale Flipped SU(5)
    ACT-05-18, MI-TH-1815
    JCAP 1904 (2019) 009

    by: Ellis, John (King's Coll. London) et al.

    No-scale supergravity and the flipped SU(5)×U(1) gauge group provide an ambitious prototype string-inspired scenario for physics below the string scale, which can accommodate the Starobinsky-like inflation favoured by observation when the inflaton is associated with one of the singlet fields associated with neutrino mass generation. During inflation, the vacuum remains in the unbroken GUT phase, and GUT symmetry breaking occurs later when a field with a flat direction (the flaton) acquires a vacuum expectation value. Inflaton decay and the reheating process depend crucially on GUT symmetry breaking, as decay channels open and close, depending on the value of the flaton vacuum expectation value. Here, we consider the simultaneous cosmological evolution of both the inflaton and flaton fields after inflation. We distinguish weak, moderate and strong reheating regimes, and calculate in each case the entropy produced as all fields settle to their global minima. These three reheating scenarios differ in the value of a Yukawa coupling that introduces mass mixing between the singlets and the 10s of SU(5). The dynamics of the GUT transition has an important impact on the production of gravitinos, and we also discuss the pattern of neutrino masses we expect in each of the three cases. Finally, we use recent CMB limits on neutrino masses to constrain the reheating models, finding that neutrino masses and the cosmological baryon asymmetry can both be explained if the reheating is strong.

  • One-loop Dirac neutrino mass and mixed axion/WIMP dark matter
    Phys.Rev. D99 (2019) 075009

    by: Carvajal, Cristian D.R. (Antioquia U.) et al.

    We consider the Peccei-Quinn (PQ) mechanism as the one behind the Dirac neutrino masses when these are generated through the d=5 effective operator L¯H˜NRϕ at one-loop level, with ϕ being a Standard Model singlet scalar. In this setup, the PQ symmetry guarantees that the one-loop realization of such an effective operator gives the leading contribution to the Dirac neutrino masses by forbidding the contributions arising from its tree-level realizations. All the mediators in the one-loop neutrino mass diagrams can be stabilized by a remnant ZN symmetry from the PQ symmetry breaking, thus forming a dark sector besides the axion sector and leading to mixed axion-WIMP dark matter scenarios.

  • Leptohadronic blazar models applied to the 2014-15 flare of TXS 0506+056
    Astrophys.J. 874 (2019) L29

    by: Rodrigues, Xavier (DESY, Zeuthen) et al.

    We investigate whether the emission of neutrinos observed in 2014–2015 from the direction of the blazar TXS 0506+056 can be accommodated with leptohadronic multiwavelength models of the source commonly adopted for the 2017 flare. While multiwavelength data during the neutrino flare are sparse, the large number of neutrino events (13 ± 5) challenges the missing activity in gamma-rays. We illustrate that two to five neutrino events during the flare can be explained with leptohadronic models of different categories: a one-zone model, a compact-core model, and an external radiation field model. If, however, significantly more events were to be accommodated, the predicted multiwavelength emission levels would be in conflict with observational X-ray constraints, or with the high-energy gamma-ray fluxes observed by the Fermi Large Area Telescope, depending on the model. For example, while the external radiation field model can predict up to five neutrino events without violating X-ray constraints, the absorption of high-energy gamma-rays is in minor tension with the data. We therefore do not find any model that can simultaneously explain the high event number quoted by IceCube and the (sparse) electromagnetic data during the neutrino flare.

  • Minimal radiative Dirac neutrino mass models
    Phys.Rev. D99 (2019) 075008

    by: Calle, Julian (Antioquia U.) et al.

    Neutrinos may be Dirac particles of which the masses arise radiatively at one loop, naturally explaining their small values. In this work, we show that all the one-loop realizations of the dimension-5 operator to effectively generate Dirac neutrino masses can be implemented by using a single local symmetry: U(1)B-L. Since this symmetry is anomalous, new chiral fermions, charged under B-L, are required. The minimal model consistent with neutrino data includes three chiral fermions, two of them with the same lepton number. The next minimal models contain five chiral fermions, and their B-L charges can be fixed by requiring a dark matter candidate in the spectrum. We list the full particle content as well as the relevant Lagrangian terms for each of these models. They are new and simple models that can simultaneously accommodate Dirac neutrino masses (at one loop) and dark matter without invoking any discrete symmetries.

  • Non-Standard Neutrino Interactions and Neutral Gauge Bosons
    SciPost Phys. 6 (2019) 038

    by: Heeck, Julian (Brussels U.) et al.

    We investigate Non-Standard Neutrino Interactions (NSI) arising from a flavor-sensitive $Z'$ boson of a new $U(1)'$ symmetry. We compare the limits from neutrino oscillations, coherent elastic neutrino-nucleus scattering, and $Z'$ searches at different beam and collider experiments for a variety of straightforward anomaly-free $U(1)'$ models generated by linear combinations of $B-L$ and lepton-family-number differences $L_\alpha-L_\beta$. Depending on the flavor structure of those models it is easily possible to avoid NSI signals in long-baseline neutrino oscillation experiments or change the relative importance of the various experimental searches. We also point out that kinetic $Z$-$Z'$ mixing gives vanishing NSI in long-baseline experiments if a direct coupling between the $U(1)'$ gauge boson and matter is absent. In contrast, $Z$-$Z'$ mass mixing generates such NSI, which in turn means that there is a Higgs multiplet charged under both the Standard Model and the new $U(1)'$ symmetry.

  • Master Majorana neutrino mass parametrization
    Phys.Rev. D99 (2019) 075019

    by: Cordero-Carrión, Isabel (Valencia U.) et al.

    After introducing a master formula for the Majorana neutrino mass matrix we present a master parametrization for the Yukawa matrices automatically in agreement with neutrino oscillation data. This parametrization can be used for any model that induces Majorana neutrino masses. The application of the master parametrization is also illustrated in an example model, with special focus on its lepton flavor violating phenomenology.

  • Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP
    Int.J.Mod.Phys. A34 (2019) 1950047

    by: Chianese, Marco (U. Amsterdam, GRAPPA) et al.

    One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay $0\nu\beta\beta$-rate on the active-sterile mixing angle are not significative for SHiP.

  • Probing neutrino Dirac mass in left-right symmetric models at the LHC and next generation colliders
    Phys.Rev. D99 (2019) 055042

    by: Helo, Juan Carlos (La Serena U.) et al.

    We assess the sensitivity of the LHC, its high energy upgrade, and a prospective 100 TeV hadronic collider to the Dirac Yukawa coupling of the heavy neutrinos in left-right symmetric models (LRSMs). We focus specifically on the trilepton final state in regions of parameter space yielding prompt decays of the right-handed gauge bosons ($W_R$) and neutrinos ($N_R$). In the minimal LRSM, the Dirac Yukawa couplings are completely fixed in terms of the mass matrices for the heavy and light neutrinos. In this case, the trilepton signal provides a direct probe of the Dirac mass term for a fixed $W_R$ and $N_R$ mass. We find that while it is possible to discover the $W_R$ at the LHC, probing the Dirac Yukawa couplings will require a 100 TeV $pp$ collider. We also show that the observation of the trilepton signal at the LHC would indicate the presence of a non-minimal LRSM scenario.

  • Revisiting constraints on 3 + 1 active-sterile neutrino mixing using IceCube data
    JHEP 1903 (2019) 203

    by: Miranda, Luis Salvador (Johannesburg U.) et al.

    Recent IceCube search results for sterile neutrino increased tension between the combined appearance and disappearance experiments. On the other hand, MiniBooNE latest data confirms at 4.9σ CL the short-baseline oscillation anomaly. We analyze published IceCube data based on two different active-sterile mixing schemes using one additional sterile neutrino flavor. We present exclusion regions in the parameter ranges 0.01 ≤ sin$^{2}$θ$_{24}$ ≤ 0.1 and 0.1 eV$^{2}$ ≤ Δm$_{42}^{2}$ ≤ 10 eV$^{2}$ for the mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing scheme, 3σ CL allowed regions for the appearance experiment and MiniBooNE latest result are excluded at ≳ 3σ CL. In case of less-restrictive flavor-mixing scheme, results from the appearance experiments are excluded at ≳ 2σ CL. We also find that including prompt component of the atmospheric neutrino flux relaxes constraints on sterile mixing for Δm$_{42}^{2}$ ≳ 1 eV$^{2}$.

  • Direct Detection Experiments at the Neutrino Dipole Portal Frontier
    Phys.Rev. D99 (2019) 075010

    by: Shoemaker, Ian M. (South Dakota U.) et al.

    Heavy sterile neutrinos are typically invoked to accommodate the observed neutrino masses, by positing a new Yukawa term connecting these new states to the neutrinos in the electroweak doublet. However, given our ignorance of the neutrino sector, we should explore additional interactions such sterile neutrinos may have with the Standard Model. In this paper, we study the dimension-5 operator which couples the heavy state to a light neutrino and the photon. We find that the recent XENON1T direct detection data can improve the limits on this “neutrino dipole portal” by up to an order of magnitude over previous bounds for tau neutrinos. Future direct detection experiments may be able to extend bounds for all three neutrino flavors down to the level probed by SN1987A.

  • Constraints on $U(1)_{L_\mu-L_\tau}$ from LHC Data
    Phys.Lett. B791 (2019) 130-136

    by: Drees, Manuel (U. Bonn, Phys. Inst., BCTP) et al.

    In this study, we apply LHC data to constrain the extension of the Standard Model by an anomaly–free U(1)Lμ−Lτ gauge group; this model contains a new gauge boson ( Z′ ) and a scalar dark matter particle ( ϕDM ). We recast a large number of LHC analyses of multi–lepton final states by the ATLAS and CMS collaborations. We find that for 10GeV
  • Constraints on Bosonic Dark Matter with Low Threshold Germanium Detector at Kuo-Sheng Reactor Neutrino Laboratory
    Chin.J.Phys. 58 (2019) 63-74

    by: Singh, Manoj Kumar (Taiwan, Inst. Phys.) et al.

    We report results from searches of pseudoscalar and vector bosonic super-weakly interacting massive particles (super-WIMP) in the TEXONO experiment at the Kuo-Sheng Nuclear Power Station, using 314.15 kg days of data from $n$-type Point-Contact Germanium detector. The super-WIMPs are absorbed and deposit total energy in the detector, such that the experimental signatures are spectral peaks corresponding to the super-WIMP mass. Measured data are compatible with the background model, and no significant excess of super-WIMP signals are observed. We derived new upper limits on couplings of electrons with the pseudoscalar and vector bosonic super-WIMPs in the sub-keV mass region, assuming they are the dominant contributions to the dark matter density of our galaxy.

  • Simple $A_4$ models for dark matter stability with texture zeros
    Phys.Rev. D99 (2019) 055044

    by: De La Vega, Leon M.G. (Mexico U.) et al.

    In a simple framework which naturally incorporates dark matter stability and neutrino phenomenology, we compute all the possible texture zeros which arise when the non-abelian flavor symmetry A4 is spontaneously broken to Z2. As a result, we obtain four textures with two vanishing matrix elements. Two of such textures predict a zero contribution to the neutrinoless double beta decay effective mass parameter at tree level, and as a one loop bound we get $m_{ee}<8\times 10^{-2}$ meV. These are compatible with the normal ordering for the neutrino masses and the allowed range for the lightest neutrino mass is between $m_{\nu_{min}}\sim3$ meV and $m_{\nu_{max}}\sim8$ meV. Additionally we obtain dark matter stability linked to the way the flavor symmetry is broken, leaving a residual Z2 symmetry

  • Surface tension of hot and dense quark matter under strong magnetic fields
    Phys.Rev. C99 (2019) 035804

    by: Lugones, G. (ABC Federal U.) et al.

    We study the surface tension of hot, highly magnetized three-flavor quark matter droplets, focusing specifically on the thermodynamic conditions prevailing in neutron stars, hot lepton-rich protoneutron stars, and neutron star mergers. We explore the role of temperature, baryon number density, trapped neutrinos, droplet size, and magnetic fields within the multiple reflection expansion formalism (MRE), assuming that astrophysical quark matter can be described as a mixture of free Fermi gases composed of quarks u, d, s, electrons, and neutrinos, in chemical equilibrium under weak interactions. We find that the total surface tension is rather unaffected by the size of the drop but is quite sensitive to the effect of baryon number density, temperature, trapped neutrinos, and magnetic fields (especially above eB∼5×10−3GeV2). Surface tensions parallel and transverse to the magnetic field span values up to ≈25MeV/fm2. For T≲100 MeV, the surface tension is a decreasing function of temperature but above 100 MeV it increases monotonically with T. Finally, we discuss some astrophysical consequences of our results.

  • Impact of polarization observables and $ B_c\to \tau \nu$ on new physics explanations of the $b\to c \tau \nu$ anomaly
    PSI-PR-18-16; TTP-18-42
    Phys.Rev. D99 (2019) 075006

    by: Blanke, Monika (KIT, Karlsruhe, IKP) et al.

    The combined analysis of the BABAR, Belle, and LHCb data on B→Dτν, B→D*τν and Bc→J/Ψτν decay observables shows evidence of physics beyond the Standard Model (SM). In this article, we study all the one- and two-dimensional scenarios which can be generated by adding a single new particle to the SM. We put special emphasis on the model-discriminating power of FL(D*) and of the τ polarizations, and especially on the constraint from the branching fraction BR(Bc→τν). We critically review this constraint and do not support the aggressive limit of BR(Bc→τν)<10% used in some analyses. While the impact of FL(D*) is currently still limited, the BR(Bc→τν) constraint has a significant impact: depending on whether one uses a limit of 60%, 30% or 10%, the pull for new physics (NP) in scalar operators changes drastically. More specifically, for a conservative 60% limit a scenario with scalar operators gives the best fit to data, while for an aggressive 10% limit this scenario is strongly disfavored and the best fit is obtained in a scenario in which only a left-handed vector operator is generated. We find a sum rule for the branching ratios of B→Dτν, B→D*τν and Λb→Λcτν which holds for any NP contribution to the Wilson coefficients. This sum rule entails an enhancement of BR(Λb→Λcτν) over its SM prediction by (24±6)% for the current R(D(*)) data.

  • Testing generalized CP symmetries with precision studies at DUNE
    Phys.Rev. D99 (2019) 075005

    by: Nath, Newton (Beijing, Inst. High Energy Phys.) et al.

    We examine the capabilities of the DUNE experiment in probing leptonic CP violation within the framework of theories with generalized CP symmetries characterized by the texture zeros of the corresponding CP transformation matrices. We investigate DUNE’s potential to probe the two least known oscillation parameters, the atmospheric mixing angle θ23 and the Dirac CP phase δCP. We fix theory-motivated benchmarks for (sin2θ23, δCP) and take them as true values in our simulations. Assuming 3.5 years of neutrino running plus 3.5 years in the antineutrino mode, we show that in all cases DUNE can significantly constrain and in certain cases rule out the generalized CP texture zero patterns.

  • Invisible neutrino decays at the MOMENT experiment
    JHEP 1904 (2019) 004

    by: Tang, Jian (Zhongshan U.) et al.

    We investigate invisible decays of the third neutrino mass eigenstate in future accelerator neutrino experiments using muon-decay beams such as MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). MOMENT has an outstanding performance to measure the deficit or excess in the spectra caused by neutrino decays, especially in $\nu_\mu$ and $\bar{\nu}_\mu$ disappearance channels. Such an experiment will improve the constraints of the neutrino lifetime $\tau_3$. Compared with exclusion limits in the current accelerator neutrino experiments T2K and NOvA under the stable $\nu$ assumption, we expect that MOMENT gives the bound of $\tau_3/m_3\ge1.46\times10^{-11}$~s/eV at $3\sigma$ confidence level, which is better than their recent limits: $\tau_3/m_3\ge 7\times10^{-13}$~s/eV in NOvA and $\tau_3/m_3\ge 1.41\times10^{-12}$~s/eV in T2K. The non-decay scenario is expected to be excluded by MOMENT at the $>3\sigma$ confidence level, if the best fit results in T2K and NOvA are confirmed. We further find that reducing systematic uncertainties is slightly more important than the running time. Finally, we find very little correlations between $\tau_3/m_3$ and other oscillation parameters, which point to an advantage of MOMENT to measure $\tau_3/m_3$.

  • Modular S$_{4}$ models of lepton masses and mixing
    SISSA 47/2018/FISI
    JHEP 1904 (2019) 005

    by: Novichkov, P.P. (INFN, Trieste) et al.

    We investigate models of charged lepton and neutrino masses and lepton mixing based on broken modular symmetry. The matter fields in these models are assumed to transform in irreducible representations of the finite modular group Γ$_{4}$ ≃ S$_{4}$. We analyse the minimal scenario in which the only source of symmetry breaking is the vacuum expectation value of the modulus field. In this scenario there is no need to introduce flavon fields. Using the basis for the lowest weight modular forms found earlier, we build minimal phenomenologically viable models in which the neutrino masses are generated via the type I seesaw mechanism. While successfully accommodating charged lepton masses, neutrino mixing angles and mass-squared differences, these models predict the values of the lightest neutrino mass (i.e., the absolute neutrino mass scale), of the Dirac and Majorana CP violation (CPV) phases, as well as specific correlations between the values of the atmospheric neutrino mixing parameter sin$^{2}$θ$_{23}$ and i) the Dirac CPV phase δ, ii) the sum of the neutrino masses, and iii) the effective Majorana mass in neutrinoless double beta decay. We consider also the case of residual symmetries ℤ$_{3}^{ST}$ and ℤ$_{2}^{S}$ respectively in the charged lepton and neutrino sectors, corresponding to specific vacuum expectation values of the modulus.

  • Probing right handed neutrinos at the LHeC and lepton colliders using fat jet signatures
    Phys.Rev. D99 (2019) 055030

    by: Das, Arindam (Korea Inst. Advanced Study, Seoul) et al.

    The inclusion of heavy neutral leptons (right-handed neutrinos) to the Standard Model (SM) particle content is one of the best motivated ways to account for the observed neutrino masses and flavor mixing. The modification of the charged and neutral currents from active-sterile mixing of the neutral leptons can provide novel signatures which can be tested at the future collider experiments. In this article, we explore the discovery prospect of a very heavy right handed neutrino to probe such extensions at the future collider experiments like Large Hadron electron Collider (LHeC) and liner collider. We consider the production of the heavy neutrino via the $t$ and $s$-channel processes and its subsequent decays into the semi-leptonic final states. We specifically focus on the scenario where the gauge boson produced from heavy neutrino decay is highly boosted, leading to a fat-jet. We study the bounds on the sterile neutrino properties from several past experiments and compare with our results.

  • Electroweak Vacuum metastability in a natural minimal Type-III Seesaw Model
    Phys.Rev. D99 (2019) 075012

    by: Goswami, Srubabati (Ahmedabad, Phys. Res. Lab) et al.

    We study the minimal type-III seesaw model in which we extend the standard model by adding two SU(2)L triplet fermions with zero hypercharge to explain the origin of the nonzero neutrino masses. We show that the naturalness conditions and the limits from lepton flavor violating decays provide very stringent bounds on the model parameters along with the constraints from the stability/metastability of the electroweak vacuum. We perform a detailed analysis of the model parameter space including all the constraints for both normal as well as inverted hierarchies of the light neutrino masses. We find that most of the regions that are allowed by lepton flavor violating decays and naturalness fall in the stable/metastable region depending on the values of the standard model parameters.

  • Fiducial polarization observables in hadronic WZ production: A next-to-leading order QCD+EW study
    JHEP 1904 (2019) 065

    by: Baglio, Julien
    We present a study at next-to-leading-order (NLO) of the process pp → W$^{±}$Z → ℓν$_{l}$ℓ$^{′+}$ℓ$^{′−}$, where ℓ, ℓ′ = e, μ, at the Large Hadron Collider. We include the full NLO QCD corrections and the NLO electroweak (EW) corrections in the double-pole approximation. We define eight fiducial polarization coefficients directly constructed from the polar-azimuthal angular distribution of the decay leptons. These coefficients depend strongly on the kinematical cuts on the transverse momentum or rapidity of the individual leptons. Similarly, fiducial polarization fractions are also defined and they can be directly related to the fiducial coefficients. We perform a detailed analysis of the NLO QCD+EW fiducial polarization observables including theoretical uncertainties stemming from the scale variation and parton distribution function uncertainties, using the fiducial phase space defined by the ATLAS and CMS experiments. We provide results in the helicity coordinate system and in the Collins-Soper coordinate system, at a center-of-mass energy of 13 TeV. The EW corrections are found to be important in two of the angular coefficients related to the Z boson, irrespective of the kinematical cuts or the coordinate system. Meanwhile, those EW corrections are very small for the W$^{±}$ bosons.

  • Neutrino recoil force in electron-capture decay of polarized nuclei: measurement prospects and potential applications
    Phys.Rev. C99 (2019) 045502

    by: Barabanov, A.L.
    Due to a directional asymmetry of neutrino emission caused by parity violation, a sample of radioactive atoms experiences a small recoil force from neutrino radiation accompanying electron capture by polarized nuclei. An expression for this force is obtained for the case of allowed nuclear transitions. Prospects to measure this force by the use of modern micromechanical devices are considered. Numerical estimates for the force are presented for a number of most suitable radioactive isotopes. Potential applications for the weak interaction studies are discussed including the possibility to search for hypothetical Lorentz invariance violation.

  • Constraining neutrino mass with tomographic weak lensing one-point probability distribution function and power spectrum
    Phys.Rev. D99 (2019) 083508

    by: Liu, Jia (Princeton U. (main)) et al.

    We forecast the constraints on the neutrino mass sum (Σmν) from the one-point probability distribution function (PDF) and power spectrum of weak lensing measurements for an Large Synoptic Survey Telescope-like survey, using MassiveNuS simulations. The PDF provides access to non-Gaussian information beyond the power spectrum. It is particularly sensitive to nonlinear growth on small scales, where massive neutrinos also have the largest effect. We find that tomography helps improve the constraint on Σmν by 14% and 32% for the power spectrum and the PDF, respectively, compared to a single redshift bin. The PDF alone outperforms the power spectrum in constraining Σmν. When the two statistics are combined, the constraint is further tightened by 35%, with respect to the power spectrum alone. We conclude that the weak lensing PDF is complementary to the power spectrum and has the potential to become a powerful tool for constraining neutrino mass. In this work, we do not include systematics such as baryon effects, intrinsic alignments, photo-z errors, and stress that they need to be carefully studied in future work.

  • Induced resonance makes light sterile neutrino Dark Matter cool
    Phys.Rev. D99 (2019) 083507

    by: Bezrukov, F. (Manchester U.) et al.

    We describe two new generation mechanisms for dark matter (DM) composed of sterile neutrinos with O(1)  keV mass. The model contains a light scalar field that coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino. In a region of model parameter space, the oscillations between active and sterile neutrinos are resonantly enhanced. This mechanism allows us to produce sterile neutrino DM with a small mixing angle with active neutrinos, thus evading the x-ray constraints. At the same time, the spectrum of produced DM is much cooler than in the case of ordinary oscillations in plasma, opening a window of lower mass DM, which is otherwise forbidden by structure formation considerations. In other regions of the model parameter space, where the resonance does not appear, another mechanism can operate: a large field suppresses the active-sterile oscillations, but instead sterile neutrinos are produced by the oscillating scalar field when the effective fermion mass crosses zero. In this case, the DM component is cold, and even the 1 keV neutrino is consistent with the cosmic structure formation.

  • Dynamical generation of neutrino mass scales
    Phys.Lett. B792 (2019) 40-42

    by: Aranda, Alfredo (Colima U.) et al.

    In this letter we present a simple scenario where the mass scales associated to atmospheric and solar neutrino oscillations are obtained through the dynamical generation of neutrino masses. The main idea is that the two different scales are the result of two independent mechanisms, namely a type-I seesaw generating the atmospheric scale and a radiative 1-loop process providing the solar one. A relation of the two scales, reminiscent of the so-called sequential dominance, is thus obtained.

  • U(1)' mediated decays of heavy sterile neutrinos in MiniBooNE
    Phys.Rev. D99 (2019) 071701

    by: Ballett, Peter (Durham U., IPPP) et al.

    The MiniBooNE low-energy excess is a longstanding problem which has received further confirmation recently with a reanalysis using newly collected data, with the anomaly now at the $4.8\sigma$ level. In this letter we propose a novel explanation which advocates a low-energy sector containing $Z^\prime$ bosons with GeV-scale masses and sterile neutrinos with masses around $100$-$500$ MeV. We show that this scenario can provide an excellent spectral agreement with the MiniBooNE low-energy excess in the form of $Z^\prime$-mediated neutral current production of heavy sterile states, a fraction of whose subsequent decay to $e^+e^-$ pairs are misidentified as single electron-like electromagnetic showers. Our model inscribes itself in the broad class of models in which sterile neutrinos are charged under novel interactions, allowing new couplings to hidden-sector physics. Alongside the electron-like MiniBooNE signature this model also predicts a novel, low-background, signal in LArTPC detectors such as MicroBooNE consisting of two distinguishable electron-like electromagnetic showers originating from a single vertex with no associated hadronic activity.

  • Neutrino Masses and Mixings Dynamically Generated by a Light Dark Sector
    Phys.Lett. B791 (2019) 210-214

    by: Bertuzzo, Enrico (Sao Paulo U.) et al.

    Neutrinos may be the harbingers of new dark sectors, since the renormalizable neutrino portal allows for their interactions with hidden new physics. We propose here to use this fact to connect the generation of neutrino masses to a light dark sector, charged under a new $U(1)_{\cal D}$ dark gauge symmetry. We introduce the minimal number of dark fields to obtain an anomaly free theory with spontaneous breaking of the dark symmetry, and obtain automatically the inverse seesaw Lagrangian. In addition, the so-called $\mu$-term of the inverse seesaw is dynamically generated and technically natural in this framework. As a bonus, the new light dark gauge boson can provide a possible explanation to the MiniBooNE anomaly.

  • Cutoff of IceCube Neutrino Spectrum due to t-channel Resonant Absorption by C$\nu$B
    JCAP 1903 (2019) 041

    by: Mohanty, Subhendra (Ahmedabad, Phys. Res. Lab) et al.

    The non-observation of neutrinos by the IceCube at the Glashow resonance energy of 6.3 PeV has been a long standing unresolved issue. In this paper we propose a t-channel neutrino absorption by the C$\nu$B, which causes a cutoff at 4.5 PeV neutrino energy, to explain the IceCube observations. We present a neutrinophilic 2HDM where the neutrino masses are generated by a low scale seesaw mechanism. A $\mathcal{O}$(10) MeV scalar mediates the interactions between left and right handed neutrinos and generates the t-channel diagram used for explaining the absence of Glashow resonance. The same scalar mediates the annihilation of the dark matter and generates the correct relic density.

  • Same-sign trilepton signal for stop quark in the presence of sneutrino dark matter
    Phys.Rev. D99 (2019) 075014

    by: Ghosh, Dilip Kumar (IACS, Kolkata) et al.

    We have explored a minimal supersymmetric standard model scenario extended by one pair of gauge singlets per generation. In the model light neutrino masses and their mixings are generated via inverse seesaw mechanism. In such a scenario, a right-handed sneutrino can be the lightest supersymmetric particle and a cold Dark Matter (DM) candidate. If Casas-Ibarra parametrisation is imposed on the Dirac neutrino Yukawa coupling matrix ($Y_{\nu}$) to fit the neutrino oscillation data, the resulting $Y_{\nu}$ is highly constrained from the lepton flavor violating (LFV) decay constraints. The smallness of $Y_{\nu}$ requires the sneutrino DM to co-annihilate with other sparticle(s) in order to satisfy DM relic density constraint. We have studied sneutrino co-annihilation with wino and observed that this sneutrino-wino compressed parameter space gives rise to a novel same-sign trilepton signal for the stop quark, which is more effective than the conventional stop search channels in the present framework. We have shown that the choice of neutrino mass hierarchy strongly affects the signal event rate, making it easier to probe the scenario with inverted mass hierarchy.

  • Multimessenger tests of Einstein's weak equivalence principle and Lorentz invariance with a high-energy neutrino from a flaring blazar
    JHEAp 22 (2019) 1-4

    by: Wei, Jun-Jie (Purple Mountain Observ.) et al.

    The detection of the high-energy ($\sim290$ TeV) neutrino coincident with the flaring blazar TXS 0506+056, the first and only $3\sigma$ neutrino-source association to date, provides new, multimessenger tests of the weak equivalence principle (WEP) and Lorentz invariance. Assuming that the flight time difference between the TeV neutrino and gamma-ray photons from the blazar flare is mainly caused by the gravitational potential of the Laniakea supercluster of galaxies, we show that the deviation from the WEP for neutrinos and photons is conservatively constrained to have an accuracy of $10^{-6}-10^{-7}$, which is 3--4 orders of magnitude better than previous results placed by MeV neutrinos from supernova 1987A. In addition, we demonstrate that the association of the TeV neutrino with the blazar flare sets limits on the energy scales of quantum gravity for both linear and quadratic violations of Lorentz invariance (LIV) to $E_{\rm QG, 1}>3.2\times10^{15}-3.7\times10^{16}$ GeV and $E_{\rm QG, 2}>4.0\times10^{10}-1.4\times10^{11}$ GeV. These improve previous limits on both linear and quadratic LIV energy scales in neutrino propagation by 5--7 orders of magnitude.

  • High-Energy Emission from Interacting Supernovae: New Constraints on Cosmic-Ray Acceleration in Dense Circumstellar Environments
    Astrophys.J. 874 (2019) 80

    by: Murase, Kohta (Kyoto U., Yukawa Inst., Kyoto) et al.

    Supernovae (SNe) with strong interactions with circumstellar material (CSM) are promising candidate sources of high-energy neutrinos and gamma rays, and have been suggested as an important contributor to Galactic cosmic rays beyond 1 PeV. Taking into account the shock dissipation by a fast velocity component of SN ejecta, we present comprehensive calculations of the non-thermal emission from SNe powered by shock interactions with a dense wind or CSM. Remarkably, we consider electromagnetic cascades in the radiation zone and subsequent attenuation in the pre-shock CSM. A new time-dependent phenomenological prescription provided by this work enables us to calculate gamma-ray, hard X-ray, radio, and neutrino signals, which originate from cosmic rays accelerated by the diffusive shock acceleration mechanism. We apply our results to SN IIn 2010jl and SN Ib/IIn 2014C, for which the model parameters can be determined from the multi-wavelength data. For SN 2010jl, the more promising case, by using the the latest Fermi Large Area Telescope (LAT) Pass 8 data release, we derive new constraints on the cosmic-ray energy fraction, <0.05-0.1. We also find that the late-time radio data of these interacting SNe are consistent with our model. Further multi-messenger and multi-wavelength observations of nearby interacting SNe should give us new insights into the diffusive shock acceleration in dense environments as well as pre-SN mass-loss mechanisms.

  • Spontaneous Breaking of Lepton Number and Cosmological Domain Wall Problem
    Phys.Rev.Lett. 122 (2019) 151301

    by: Lazarides, George (Aristotle U., Thessaloniki) et al.

    We show that if global lepton number symmetry is spontaneously broken in a post inflation epoch, then it can lead to the formation of cosmological domain walls. This happens in the well-known "Majoron paradigm" for neutrino mass generation. We propose some realistic examples which allow spontaneous lepton number breaking to be safe from such domain walls.

  • Linear seesaw model with hidden gauge symmetry
    APCTP Pre2018 - 009
    Phys.Rev. D99 (2019) 055033

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

    We propose a natural realization of linear seesaw model with hidden gauge symmetry in which $SU(2)_L$ triplet fermions, one extra Higgs singlet, doublet and quartet scalar are introduced. Small neutrino mass can be realized by two suppression factors that are small vacuum expectation value of quartet scalar and inverse of Dirac mass for triplet. After formulating neutrino mass matrix, we discuss collider phenomenology of the model focusing on signals from exotic charged particles production at the LHC.

  • Scientific Works of Shoichi Sakata and Commentaries

    by: Maskawa, Toshihide (Nagoya U.)

  • Active and sterile neutrino phenomenology with $A_4$ based minimal extended seesaw
    Nucl.Phys. B941 (2019) 755-779

    by: Das, Pritam (Tezpur U.) et al.

    We study a model of neutrino within the framework of minimal extended seesaw (MES), which plays an important role in active and sterile neutrino phenomenology in (3+1) scheme. The A4 flavor symmetry is augmented by additional Z4×Z3 symmetry to constraint the Yukawa Lagrangian of the model. We use non-trivial Dirac mass matrix, with broken μ−τ symmetry, as the origin of leptonic mixing. Interestingly, such structure of mixing naturally leads to the non-zero reactor mixing angle θ13 . Non-degenerate mass structure for right-handed neutrino MR is considered so that we can further extend our study to Leptogenesis. We have also considered three different cases for sterile neutrino mass, MS to check the viability of this model, within the allowed 3 σ bound in this MES framework.

  • Asymmetric Dark Matter, Inflation and Leptogenesis from $B-L$ Symmetry Breaking
    Phys.Rev. D99 (2019) 055040

    by: Van Dong, Phung (Hanoi Ed. U.) et al.

    We propose a unified setup for dark matter, inflation and baryon asymmetry generation through the neutrino mass seesaw mechanism. Our scenario emerges naturally from an extended gauge group containing $B-L$ as a non-commutative symmetry, broken by a singlet scalar that also drives inflation. Its decays reheat the universe, producing the lightest right-handed neutrino. Automatic matter parity conservation leads to the stability of an asymmetric dark matter candidate, directly linked to the matter-antimatter asymmetry in the universe.

  • B–L Model with $\mathbf{S}_{3}$ symmetry: Nearest Neighbor Interaction Textures and Broken $\mu\leftrightarrow\tau$ Symmetry
    Eur.Phys.J. C79 (2019) 285

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

    We make a scalar extension of the B–L gauge model where the $\mathbf{S}_{3}$ 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 interaction (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, which comes from type I see-saw mechanism, provides a non-maximal atmospheric angle and a non-zero reactor angle.

  • Particle physics origin of the 5 MeV bump in the reactor antineutrino spectrum?
    Phys.Rev. D99 (2019) 055045

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

    One of the most puzzling questions in neutrino physics is the origin of the excess at 5 MeV in the reactor antineutrino spectrum. In this paper, we explore the excess via the reaction $^{13}$C$(\overline{\nu}, \overline{\nu}^\prime n)^{12}$C$^*$ in organic scintillator detectors. The de-excitation of $^{12}$C$^*$ yields a prompt $4.4$ MeV photon, while the thermalization of the product neutron causes proton recoils, which in turn yield an additional prompt energy contribution with finite width. Together, these effects can mimic an inverse beta decay event with around 5 MeV energy. We consider several non-standard neutrino interactions to produce such a process and find that the parameter space preferred by Daya Bay is disfavored by measurements of neutrino-induced deuteron disintegration and coherent elastic neutrino-nucleus scattering. While non-minimal particle physics scenarios may be viable, a nuclear physics solution to this anomaly appears more appealing.

  • Dark Matter, Neutrino mass, Cutoff for Cosmic-Ray Neutrino, and Higgs Boson Invisible Decay from a Neutrino Portal Interaction
    Chin.Phys. C43 (2019) 045101

    by: Yin, Wen (Beijing, Inst. High Energy Phys.)

    We study an effective theory beyond the standard model (SM) where either of two additional gauge singlets, a Majorana fermion and a real scalar, constitutes all or some fraction of dark matter. In particular, we focus on the masses of the two singlets in the range of O(10) MeV-O(10) GeV, with a neutrino portal interaction which plays important roles not only in particle physics but also in cosmology and astronomy. We point out that the dark matter abundance can be thermally explained with (co)annihilation, where the dark matter with a mass greater than 2 GeV can be tested in future lepton colliders, CEPC, ILC, FCC-ee and CLIC, in the light of the Higgs boson invisible decay. When the gauge singlets are lighter than O(100)MeV, the interaction can affect the neutrino propagation in the universe due to its annihilation with the cosmic background neutrino into the gauge singlets. Although can not be the dominant dark matter in this case, the singlets are produced by the invisible decay of the Higgs boson at a rate fully within the reach of the future lepton colliders. In particular, a high energy cutoff of cosmic-ray neutrino, which may account for the non-detection of Greisen-Zatsepin-Kuzmin (GZK) neutrinos or non-observation of Glashow resonance, can be set. Interestingly, given the cutoff and the mass (range) of the WIMP, a neutrino mass can be "measured" kinematically.

  • Radiative neutrino mass in an alternative $U(1)_{B-L}$ gauge symmetry
    Nucl.Phys. B941 (2019) 586-599

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

    We propose a neutrino model in which neutrino masses are generated at one loop level and three right-handed fermions have non-trivial charges under $U(1)_{B-L}$ gauge symmetry in no conflict with anomaly cancellation. After the spontaneously symmetry breaking, a remnant $Z_2$ symmetry is induced and plays an role in assuring the stability of dark matter candidate.

  • A Two Loop Radiative Neutrino Model
    Nucl.Phys. B941 (2019) 744-754

    by: Baek, Seungwon (Korea Inst. Advanced Study, Seoul) et al.

    We explore the possibility to explain a bosonic dark matter candidate with a gauge singlet inside the loop to generate the neutrino mass matrix at two-loop level. The mass matrix is suppressed by a small mixing that comes from the bound on {direct detection experiments of the dark matter, and equivalent of the three-loop neutrino model due to the small mixing between neutral inert bosons. Here, our setup is} the Zee-Babu type scenario with $Z_3$ discrete symmetry, in which we consider the neutrino oscillation data, lepton flavor violations, muon $g-2$, $\mu-e$ conversion rate, lepton flavor-changing and conserving $Z$ boson decay and bosonic dark matter candidate.

  • Echo Technique to Distinguish Flavors of Astrophysical Neutrinos
    Phys.Rev.Lett. 122 (2019) 151101

    by: Li, Shirley Weishi (Ohio State U.) et al.

    The flavor composition of high-energy astrophysical neutrinos is a rich observable. However, present analyses cannot effectively distinguish particle showers induced by $\nu_e$ versus $\nu_\tau$. We show that this can be accomplished by measuring the intensities of the delayed, collective light emission from muon decays and neutron captures, which are, on average, greater for $\nu_\tau$ than for $\nu_e$. This new technique would significantly improve tests of the nature of astrophysical sources and of neutrino properties. We discuss the promising prospects for implementing it in IceCube and other detectors.

  • Particle quantum states with indefinite mass and neutrino oscillations
    Annals Phys. 403 (2019) 82-105

    by: Lobanov, A.E. (Moscow State U.)

    The Hilbert spaces of particle states are constructed in such a way that the neutrinos are combined in a multiplet with its components being considered as different quantum states of a single particle. The same is done for the charged leptons and the down- and up-type quarks. In a theory based on the Lagrangian of the fermion sector of the Standard Model modified in accordance with this construction, the phenomenon of neutrino oscillations arises as a direct consequence of the general principles of quantum field theory. By the example of the pion decay it is shown that the states of the neutrino produced in the decay process can be described by a superposition of states with different masses and identical canonical momenta with very high accuracy.

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of Grants click here