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  • Constraints on the charged Higgs bosons from the 221 LFNU model
    J.Phys. G46 (2019) 075001

    by: Yue, Chong-Xing (Liaoning Normal U.) et al.

    The model with lepton flavor non-universality can generate the active neutrino masses via the Zee mechanism, which predicts the existence of the charged Higgs bosons by introducing new free parameters and M h where i, j denote e, μ, or τ. We calculate the contributions of to the , , and decays, and extract individual constraints on the factor /M h by combining the current experimental measurements. We find that can provide more stringent constraints on /M h than , while the obtained constraints on /M h are comparable from these decays. The contributions of to the muon anomalous magnetic moment a μ and non-standard interactions of neutrinos are also discussed.

  • Understanding of two-zero textures of neutrino mass matrices in minimal extended seesaw mechanism and their symmetry realization
    Int.J.Mod.Phys. A34 (2019) 1950059

    by: Patgiri, Mahadev (Assam U.) et al.

    We study the texture zeros of 4 × 4 neutrino mass matrices Mν in the minimal extended type-I seesaw (MES) mechanism, incorporating one extra gauge singlet field “S”. The 4 × 4  MES model deals with 3 × 3  (MD), 3 × 3  (MR) and 1 × 3 mass matrix (MS) which couples the right-handed neutrinos and the singlet field “S”. We carry out the mapping of all possible zero textures of MD, MR and MS with the restriction to phenomenologically predictive cases having total eight zeros of MD and MR studied in the literature. If ms, the sterile neutrino mass, is subject to any limit, further block diagonalization of Mν shall not be allowed to reduce it to a 3 × 3 matrix. In 4 × 4  Mν scenario, the study of texture zero is totally different and interesting. With this motivation, we consider the (4 + 4) scheme where the digits of the pair represent the number of zeros of MD and MR, respectively, along with the one/two-zero textures of MS. There are a large number of possibilities of zeros of fermion mass matrices, but the implementation of S3 transformations reduces it to a very minimum number of basic structures. As the 4 × 4 MES matrix is a matrix of rank 3, so we consider only those textures with two zeros which are of rank 3 whereby the number of feasible zero textures reduces to 12, out of 15. On realizing these 12 textures under MES mechanism with (4 + 4) picture, we arrive at certain correlations for each texture. We examine the viability of each texture by scanning their respective correlations under recent neutrino oscillation data. Also, we discuss the interplay of Dirac and Majorana CP phases in determining the viability of a texture. The allowed two-zero textures are finally realized using a discrete Abelian flavor symmetry group Z9 with the extension of Standard Model to include some scalar fields.

  • Measuring the heavy neutrino oscillations in rare W boson decays at the Large Hadron Collider

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

    Majorana neutrinos in the seesaw model can have sizable mixings through which they can be produced at the Large Hadron Collider (LHC) and show a remarkable Lepton Number Violating (LNV) signature. In this article we study the LNV decay of the W boson via two almost degenerate heavy on-shell Majorana neutrinos $N_j$, into three charged leptons and a light neutrino. We consider the scenario where the heavy neutrino masses are within $1$ GeV $\leq M_N \leq 10$ GeV. We evaluated the possibility to measure a LNV oscillation process in such a scenario, namely, the modulation of the quantity $d \Gamma/d L$ for the process at the LHC where $W^{\pm} \to \mu^{\pm} N \to \mu^{\pm} \tau^{\pm} W^{\mp *}$ $ \to \mu^{\pm} \tau^{\pm} e^{\mp} \nu_e$. $L$ is the distance within the detector between the two vertices of the process. We found out some realistic conditions under which such a modulation could be probed at the LHC.

  • A 3-3-1 model with low scale seesaw mechanisms

    by: Cárcamo Hernández, A.E. (Santa Maria U., Valparaiso) et al.

    We construct a viable 3-3-1 model with two $SU(3)_L$ scalar triplets, extended fermion and scalar spectrum, based on the $T^{\prime}$ family symmetry and other auxiliary cyclic symmetries, whose spontaneous breaking yields the observed pattern of SM fermion mass spectrum and fermionic mixing parameters. In our model the SM quarks lighter than the top quark, get their masses from a low scale Universal seesaw mechanism, the SM charged lepton masses are produced by a Froggatt-Nielsen mechanism and the small light active neutrino masses are generated from an inverse seesaw mechanism. The model is consistent with the low energy SM fermion flavor data and successfully accommodates the current Higgs diphoton decay rate and predicts charged lepton flavor violating decays within the reach of the forthcoming experiments.

  • CP violation and quark-lepton complementarity of the neutrino mixing matrix
    Eur.Phys.J. C79 (2019) 385

    by: Zhukovsky, K. (Moscow State U.) et al.

    The comparative analysis of the neutrino mixing in the standard, cobimaximal and exponential parameterizations is performed. With the latest November 2018 data the logarithm of the mixing matrix is computed and the exact entries for the exponential matrix are obtained. The factorization of the real rotation and the CP violation in the exponential form of the mixing matrix is demonstrated. Quark-lepton complementarity hypothesis is reformulated, involving three mixing angles in the framework of the exponential parameterisation of the mixing matrix. It is shown that the cobimaximal parameterization, consistent with recent experimental data on neutrino mixing with the spread $3\sigma $ , can provide exact quark-lepton complementarity based on the data for all three mixing angles. The dependence of the CP violation degree on the parameterization parameters in the standard and the exponential forms is studied with the help of the Jarlskog invariant.

  • Prospects for Dark Boson at the LHC

    by: Roy, Himadri (Indian Inst. Tech., Kanpur)

    Non-Abelian vector boson dark matter(DM), arising from an $SU(2)_N$ extension of the Standard Model(SM) has been studied. The DM is stabilized by imposing an extra discrete global $S^{'}$ charge, which gives rise to an unbroken $S=S^{'}+T_{3N}$ even when $SU(2)_N$ is completely broken. This model, apart from a single-component DM also offers a two-component DM augmented by a scalar and a vector boson, which lives over a large parameter space evading strong direct search bounds. Apart from potential DM candidates, this model also explains the generation of light neutrino masses through the $inverse$ $seesaw$ $mechanism$. We have computed tree-unitarity bound to limit the scalar mass spectrum in our model. Phenomenological aspects of the model have been discussed. Further, we have analyzed the possible collider signatures at the Large Hadron Collider (LHC) and its future implications.

  • Compact Perturbative Expressions for Oscillations with Sterile Neutrinos in Matter

    by: Parke, Stephen J (Fermilab) et al.

    We extend a simple and compact method for calculating the three flavor neutrino oscillation probabilities in uniform matter density to schemes with sterile neutrinos, with favorable features inherited. The only constraint of the extended method is that the scale of the matter potential is not significantly larger than the atmospheric $\Delta m^2$, which is satisfied by all the running and proposed accelerator oscillation experiments. Degeneracy of the zeroth order eigensystem around solar and atmospheric resonances are resolved. Corrections to the zeroth order results are restricted to no larger than the ratio of the solar to the atmospheric $\Delta m^2$. The zeroth order expressions are exact in vacuum because all the higher order corrections vanish when the matter potential is set zero. Also because all the corrections are continuous functions of matter potential, the zeroth order precision is much better than $\Delta m^2_\odot/\Delta m^2_\text{atm}$ for weak matter effect. Numerical tests are presented to verify the theoretical predictions of the exceptional features. Moreover, possible applications of the method in experiments to check the existence of sterile neutrinos are discussed.

  • Scotogenic Cobimaximal Dirac Neutrino Mixing from $\Delta(27)$ and $U(1)_\chi$
    UCRHEP-T598 (May 2019)

    by: Ma, Ernest (UC, Riverside)

    In the context of $SU(3)_C \times SU(2)_L \times U(1)_Y \times U(1)_\chi$, where $U(1)_\chi$ comes from $SO(10) \to SU(5) \times U(1)_\chi$, supplemented by the non-Abelian discrete $\Delta(27)$ symmetry for three lepton families, Dirac neutrino masses and their mixing are radiatively generated through dark matter. The gauge $U(1)_\chi$ symmetry is broken spontaneously. The discrete $\Delta(27)$ symmetry is broken softly and spontaneously. Together, they result in two residual symmetries, a global $U(1)_L$ lepton number and a dark symmetry, which may be $Z_2$, $Z_3$, or $U(1)_D$ depending on what scalar breaks $U(1)_\chi$. Cobimaximal neutrino mixing, i.e. $\theta_{13} \neq 0$, $\theta_{23} = \pi/4$, and $\delta_{CP} = \pm \pi/2$, may also be obtained.

  • Distinguishing Dirac and Majorana neutrinos by their gravi-majoron decays

    by: Funcke, Lena (Perimeter Inst. Theor. Phys.) et al.

    Neutrinos may acquire small Dirac or Majorana masses by new low-energy physics in terms of the chiral gravitational anomaly, as proposed by Dvali and Funcke (2016). This model predicts fast neutrino decays, $\nu_i\to\nu_j+\phi$ and $\nu_i\to\overline{\nu}_j+\phi$, where the gravi-majorons $\phi$ are pseudoscalar Nambu-Goldstone bosons. The final-state neutrino and antineutrino distributions differ depending on the Dirac or Majorana mass of the initial state. This opens a channel for distinguishing these cases, for example in the spectrum of high-energy astrophysical neutrinos. In passing, we put strong bounds on the decay of the heaviest neutrino to a light pseudoscalar, ${\tau_3}/{m_3}> 2.2\times 10^{-5}{{\rm s}}/{{\rm eV}}$ at 90% CL, using data from experiments searching for antineutrino appearance from the Sun.

  • A Portalino to the Twin Sector

    by: Liu, Di (New York U., CCPP) et al.

    Extensions of the Standard Model are often highly constrained by cosmology. The presence of new states can dramatically alter observed properties of the universe by the presence of additional matter or entropy. In particular, attempts too solve the hierarchy problem through naturalness invariably predict new particles near the weak scale which come into thermal equilibrium. Without a means to deposit this energy into the SM, these models are often excluded. Scenarios of "neutral naturalness" especially, such as the Twin Higgs frequently suffer from this. However, the Portalino, a singlet fermion that marries gauge neutral fermion operators, can naturally help provide a portal for entropy to return to the SM and to lift fermionic degrees of freedom in the Twin Sector. Together with spontaneous breaking of the $Z_2$ ${\rm SM \leftrightarrow {\rm Twin}}$ symmetry, there are new opportunities to confront the cosmological challenges of these models. Here, we attempt to develop such ideas. We shall show how one can lift many of the light fields by breaking $Z_2$ with a $U(1)_Y$ scalar and its Twin partner. The introduction of Portalinos can lift the remaining degrees of freedom. We shall find that such models are highly constrained by precision SM measurements, motivating moderate extensions beyond this. We will discuss two, one with additional weak matter and another with additional colored matter. The weak model will involve simple two Higgs doublet models on top of $Z_2$ breaking. The strong model will involve the presence of new leptoquarks and diquarks. We will discuss the implications for neutrino masses from radiative corrections and possible colored signals even within these models of neutral naturalness, some of which might appear at the LHC or future colliders.

  • Neutrino Mixing via the Neutrino Portal

    by: Smirnov, Alexei Y. (Heidelberg, Max Planck Inst.)

    Relation between the lepton and quark mixings: $U_{PMNS} \approx V_{CKM}^{\dagger} U_X$, where $U_X$ is the BM or TBM mixing matrices, implies the quark-lepton (Grand) unification and existence of hidden sector with certain flavor symmetries. The latter couples to the visible sector via the neutrino portal and is responsible for $U_X$, as well as for smallness of neutrino mass. GUT ensures appearance of $\sim V_{CKM}$ in the lepton mixing. General features of this scenario (inverse or double seesaw, screening of the Dirac structures, basis fixing symmetry) are described and two realizations are presented. The high energy realization is based on $SO(10)$ GUT with the hidden sector at the Planck scale. The low energy realization includes the 100 TeV scale $L-R$ symmetry and the hidden sector at the keV - MeV scale.

  • Phase broken $\mu-\tau$ symmetry and the neutrino mass hierarchy

    by: Chamoun, N. (HIAST) et al.

    Inspired by the neutrino oscillations data, we consider the exact $\mu-\tau$ symmetry, implemented at the level of the neutrino mass matrix, as a good initial framework around which to study and describe neutrino phenomenology. Working in the diagonal basis for the charged leptons, we deviate from $\mu-\tau$ symmetry by just modifying the phases of the neutrino mass matrix elements. This deviation is enough to allow for a non-vanishing neutrino mixing entry $|V_{e3}|$ (i.e. $\theta_{13}$) but it also gives a very stringent (and eventually falsifiable) prediction for the atmospheric neutrino mixing angle $|V_{\mu3}|$ as a function of $|V_{e3}|$. We also find that when the breaking by phases is limited to a single phase, this can lead to interesting upper or lower bounds on the allowed mass for the lightest neutrino depending on the ordering of neutrino masses (normal or inverted) and on the value of the Dirac ${\cal CP}$ violating phase $\delta_{CP}$. The allowed parameter space for the effective Majorana neutrino mass $m_{ee}$ is also severely constrained in that case

  • A radiative neutrino mass model with hidden gauge symmetry inducing semi-annihilating dark matter
    APCTP Pre2019 - 009

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

    We propose two-loop neutrino mass model with gauged hidden $U(1)$ symmetry, and discuss a Majorana type of dark matter candidate that has semi-annihilation processes in the relic density as well as lepton flavor violations and muon anomalous magnetic moment. Also, we demonstrate global analysis to satisfy neutrino oscillation data, lepton flavor violations, and relic density of dark matter candidate and show that semi-annihilation modes play a crucial role in finding observed relic density.

  • Measuring dark matter-neutrino relative velocity on cosmological scales

    by: Zhu, Hong-Ming (UC, Berkeley (main)) et al.

    We present a new method to measure neutrino masses using the dark matter-neutrino relative velocity. The relative motion between dark matter and neutrinos results in a parity-odd bispectrum which can be measured from cross correlation of different cosmic fields. This new method is not affected by most systematics which are parity even and not limited by the knowledge of optical depth to the cosmic microwave background. We estimate the detectability of the relative velocity effect and find the minimal sum of neutrino masses could be detected at high significance with upcoming surveys.

  • Heavy Neutral Leptons from low-scale seesaws at the DUNE Near Detector

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

    Heavy nearly-sterile neutrinos are a common ingredient in extensions of the Standard Model which aim to explain neutrino masses, like for instance in Type I seesaw models, or one of its variants. If the scale of the new Heavy Neutral Leptons (HNLs) is sufficiently low, observable signatures can arise in a range of current and upcoming experiments, from the LHC to neutrino experiments. In this article, we discuss the phenomenology of sterile neutrinos in the MeV to GeV mass range, focusing on their decays. We embed our discussion in a realistic mass model and consider the resulting implications. We focus in particular on the impact on the signal of the strong polarisation effects in the beam for Majorana and (pseudo-)Dirac states, providing formulae to incorporate these in both production and decay. We study how the Near Detector of the upcoming Deep Underground Neutrino Experiment (DUNE) can constrain HNL states by searching for their decay products inside the detector. We conduct a Monte Carlo background analysis for the most promising signatures, incorporating the detector's particle identification capabilities, and estimate the experimental sensitivity of DUNE to these particles. We also present an estimate of the $\nu_\tau$-derived HNL flux at DUNE, currently missing in the literature, which allows us to discuss searches for HNLs at higher masses.

  • Constraining a general U(1)$^\prime$ inverse seesaw model from vacuum stability, dark matter and collider

    by: Das, Arindam (Osaka U.) et al.

    We consider a class of gauged $U(1)$ extensions of the Standard Model (SM), where the light neutrino masses are generated by an inverse seesaw mechanism. In addition to the three right handed neutrinos, we add three singlet fermions and demand an extra $Z_2$ symmetry under which, the third generations of both of the neutral fermions are odd, which in turn gives us a stable dark matter candidate. We express the $U(1)$ charges of all the fermions in terms of the U(1) charges of the standard model Higgs and the new complex scalar. We study the bounds on the parameters of the model from vacuum stability, perturbative unitarity, dark matter relic density and direct detection constraints. We also obtain the collider constraints on the $Z'$ mass and the $U(1)'$ gauge coupling. Finally we compare all the bounds on the $Z'$ mass versus the $U(1)'$ gauge coupling plane.

  • The Migdal Effect and Photon Bremsstrahlung in effective field theories of dark matter direct detection and coherent elastic neutrino-nucleus scattering

    by: Bell, Nicole F. (ARC, CoEPP, Melbourne) et al.

    Dark matter direct detection experiments have limited sensitivity to light dark matter (below a few GeV), due to the challenges of lowering energy thresholds for the detection of nuclear recoil to below $\mathcal{O}(\mathrm{keV})$. While impressive progress has been made on this front, light dark matter remains the least constrained region of dark-matter parameter space. It has been shown that both ionization and excitation due to the Migdal effect and coherently-emitted photon bremsstrahlung from the recoiling atom can provide observable channels for light dark matter that would otherwise have been missed owing to the resulting nuclear recoil falling below the detector threshold. In this paper we extend previous work by calculating the Migdal effect and photon bremmstrahlung rates for a general set of interaction types, including those that are momentum-independent or -dependent, spin-independent or -dependent, as well as examining the rates for a variety of target materials, allowing us to place new experimental limits on some of these interaction types. Additionally, we include a calculation of these effects induced by the coherent scattering on nuclei of solar or atmospheric neutrinos. We demonstrate that the Migdal effect dominates over the bremsstrahlung effect for all targets considered for interactions induced by either dark matter or neutrinos. This reduces photon bremsstrahlung to irrelevancy for future direct detection experiments.

  • CP Properties of Leptons within the Mirror Mechanism
    Phys.Atom.Nucl. 82 (2019) 144-152

    by: Dyatlov, I.T. (St. Petersburg, INP)

    The formation of the quark and lepton mass matrices through intermediate states of heavy mirror fermions is able to reproduce basic observable qualitative properties of weak-mixing matrices—specifically, the Cabibbo—Kobayashi—Maskawa (CKM) matrix and the Pontecorvo—Maki—Nakagawa-Sakata (PMNS) matrix. The reproduction in question includes the hierarchy of the CKM matrix elements and a general form of the PMNS matrix, including the smallness of the neutrino mixing angle θ$_{13}$ and leads to extremely small neutrino masses. For leptons, these properties arise only if Standard Model neutrinos are Dirac particles and if the spectrum of their generations has an inverse character. In such a lepton system, the mechanism of spontaneous mirror-symmetry violation and the observed mass hierarchy of charged leptons (e, μ, and τ) specify the structure of the PMNS matrix and make it possible to estimate the complex-valuedness of its elements—that is, to assess the CP properties of leptons. In this case, the PMNS matrix does not involve Majorana phases, whereas its Dirac phase δ$_{CP}$ corresponds to ∣ sin δ$_{CP}$ ∣ that is substantially smaller than unity.

  • Can the ANITA anomalous events be due to new physics?

    by: Cline, James M. (McGill U.) et al.

    The ANITA collaboration has observed two ultra-high-energy upgoing air shower events that cannot originate from Standard Model neutrinos that have traversed the Earth. Several beyond-the-standard-model physics scenarios have been proposed as explanations for these events. In this paper we present some general arguments making it challenging for new physics to explain the events. One exceptional class of models that could work is pointed out, in which metastable dark matter decays to a highly boosted lighter dark matter particle, that can interact in the Earth to produce the observed events.

  • Superheavy Dark Matter and ANITA's Anomalous Events

    by: Hooper, Dan (Fermilab) et al.

    The ANITA experiment, which is designed to detect ultra-high energy neutrinos, has reported the observation of two anomalous events, directed at angles of $27^{\circ}$ and $35^{\circ}$ with respect to the horizontal. At these angles, the Earth is expected to efficiently absorb ultra-high energy neutrinos, making the origin of these events unclear and motivating explanations involving physics beyond the Standard Model. In this study, we consider the possibility that ANITA's anomalous events are the result of Askaryan emission produced by exotic weakly interacting particles scattering elastically with nuclei in the Antarctic ice sheet. Such particles could be produced by superheavy ($\sim 10^{10}-10^{13}$ GeV) dark matter particles decaying in the halo of the Milky Way. Such scenarios can be constrained by existing measurements of the high-latitude gamma-ray background and the ultra-high energy cosmic ray spectrum, along with searches for ultra-high energy neutrinos by IceCube and other neutrino telescopes.

  • Sensitivity bounds on heavy neutrino mixing $|U_{\mu N}|^2$ and $|U_{\tau N}|^2$ from LHCb upgrade

    by: Cvetic, Gorazd (CCTVal, Valparaiso) et al.

    Decays of heavy pseudoscalar mesons $B$, $B_c$, $B_s$ and $D_s$ at LHCb upgrade are considered, which produce either two equal sign muons or taus. In addition, we consider the analogous decays with opposite sign muons or taus. All these decays are considered to be mediated by a heavy on-shell neutrino $N$. Such decays of $B$ mesons, if not detected, will give in general stringent upper bounds on the heavy-light mixing parameter $|U_{\mu N}|^2$ as a function of the neutrino mass $M_N \sim 1$ GeV, principally due to the large expected number of produced mesons $B$. While some of the decays of the other mentioned mesons are attractive due to a weaker CKM-suppression, the expected produced number of such mesons is significantly smaller that that of $B$'s; therefore, the sensitivity bounds from such decays are in general comparable or less restrictive. When $\tau$ pairs are produced, only two types of such decays are significant: $B, B_{c} \to \tau \tau \pi$, giving us stringent upper bounds on $|U_{\tau N}|^2$; the other decays with a pair of $\tau$, such as $B \to D^{(*)} \tau \tau \pi$, are prohibited or very suppressed by kinematics.

  • Majorana neutrino masses in gauge-Higgs unification

    by: Hasegawa, K. (Kobe U.)

    The theory that the extra-space component of the gauge field is identified with the standard model Higgs boson, is called the gauge-Higgs unification (GHU) scenario. We examine how the small neutrino masses are naturally generated in the GHU framework. We find out two model classes where the following matter multiplets are introduced : 1. adjoint rep. lepton $\Psi_{A}$, 2. fundamental rep. lepton $\Psi_{F}$ and scalar $\Sigma_{F}$. We present a concrete model in each class. At the model in class 1, the neutrino masses are generated by the admixture of the seesaw mechanism type-I and -III. At the model in class 2, the masses are generated by the inverse seesaw mechanism.

  • High energy muons in extensive air showers

    by: Gámez, C. (CAFPE, Granada) et al.

    The production of very high energy muons inside an extensive air shower is observable at neutrino telescopes and sensitive to the composition of the primary cosmic ray. Here we discuss five different sources of these muons: pion and kaon decays; charmed hadron decays; rare decays of unflavored mesons; photon conversion into a muon pair; and photon conversion into a J/psi vector meson decaying into muons. We solve the cascade equations for a $10^{10.5}$ GeV proton primary and find that unflavored mesons and gamma conversions are the two main sources of $E > 10^9$ GeV muons, while charm decays dominate at $10^5$ GeV $ < E < 10^9$ GeV. In inclined events one of these muons may deposite a large fraction of its energy near the surface, implying anomalies in the longitudinal profile of the shower and in the muon to electron count at the ground level. In particular, we show that 1 out of 300 proton showers of $10^{10.5}$ GeV will include an $E > 10^7$ GeV deposition within 500 g/cm$^2$. We also show that the production of high energy muons is very different in proton, iron or photon showers. In particular, conversions $\gamma \to \mu^+ \mu^-$ are the main source of $E > 10^5$ GeV muons in photon showers.

  • Clockwork origin of neutrino mixings

    by: Kitabayashi, Teruyuki (Tokai U., Hiratsuka)

    The clockwork mechanism provides a natural way to obtain hierarchical masses and couplings in a theory. We propose a clockwork model which has nine clockwork generations. In this model, the candidates of the origin of the neutrino mixings is nine Yukawa mass matrix elements $Y^{a\beta}$ which connect neutrinos and clockwork fermions, nine clockwork mass ratios $q_{a\beta}$ and nine numbers of clockwork fermions $n_{a\beta}$, where $a, \beta=1,2,3$. Assuming $|Y^{a\beta}|=1$, the neutrino mixings are originate from pure clockwork sector. We show that the observed neutrino mixings are exactly obtained from a clockwork model in the case of $q_{a\beta}$ origin scenario. In the $n_{a\beta}$ origin scenario, the correct order of magnitude of the observed neutrino mixings are obtained from a clockwork model.

  • NuOscProbExact: a general-purpose code to compute exact two-flavor and three-flavor neutrino oscillation probabilities

    by: Bustamante, Mauricio (Bohr Inst.)

    In neutrino oscillations, a neutrino created with one flavor can be later detected with a different flavor, with some probability. In general, the probability is computed exactly by diagonalizing the Hamiltonian operator that describes the physical system and that drives the oscillations. Here we use an alternative method developed by Ohlsson & Snellman to compute exact oscillation probabilities, that bypasses diagonalization, and that produces expressions for the probabilities that are straightforward to implement. The method employs expansions of quantum operators in terms of SU(2) and SU(3) matrices. We implement the method in the code NuOscProbExact, which we make publicly available. It can be applied to any closed system of two or three neutrino flavors described by an arbitrary time-independent Hamiltonian. This includes, but is not limited to, oscillations in vacuum, in matter of constant density, with non-standard matter interactions, and in a Lorentz-violating background.

  • Probing the Decoupled Seesaw Scalar in Rare Higgs Decay

    by: Gao, Yu (Beijing, Inst. High Energy Phys.) et al.

    The Higgs boson can mix with a singlet scalar that dynamically generates the Majorana mass of the right-handed neutrino $N_R$. This mixing allows for Higgs-mediated pair production of $N_R$ without significant mixing between the active neutrinos and $N_R$. We show that even a tiny mixing between `decoupled' Higgs and singlet sectors can be testable at $pp$ colliders via the characteristic two same-sign same-flavor lepton pairs, plus missing energy signal. This rare Higgs decay provides a clean channel to probe the singlet scalar and explore the origin of neutrino masses.

  • Neutrino masses, leptogenesis and dark matter

    by: Di Bari, Pasquale (Southampton U.)

    Despite the lack of evidence of new physics at colliders, neutrino masses, dark matter and matter-antimatter asymmetry of the universe require an extension of the Standard Model. After discussing some new concepts and tools in the description of seesaw neutrino models, such as motion in flavour lepton space and the introduction of the bridging matrix that nicely complements the orthogonal matrix, I discuss recent developments in the connections between neutrino data and scenarios of leptogenesis within some well motivated extensions of the Standard Model. Finally, I briefly review a simple unified picture of neutrino masses, leptogenesis and dark matter based on an extension of the seesaw Lagrangian where a non-renormalizable effective operator coupling right-handed neutrinos to the Higgs is introduced. This operator enhances the right-handed neutrino mixing between a coupled heavy right-handed neutrino and a decoupled one playing the role of dark matter. Interference between the two coupled RH neutrinos generate usual $C\!P$ violation so that one can also achieve successful leptogenesis. Although the dark matter right-handed neutrino escapes direct and collider searches, its decays produce a detectable contribution to the very high energy neutrino flux now discovered by IceCube, so that the model is predictive and can be tested at neutrino telescopes.

  • On the Minimal Mixing of Heavy Neutrinos

    by: Drewes, Marco (Louvain U., CP3)

    We revisit the constraints on the properties of right handed neutrinos from the requirement to explain the observed light neutrino oscillation data in the type-I seesaw model. We use well-known relations to show that there is in general no lower bound on the mixing of a given heavy neutrino with any individual Standard Model generation. Lower bounds quoted in the literature only apply if the masses of the heavy neutrinos are so degenerate that they cannot be distinguished experimentally. A lower bound on the total mixing (summed over Standard Model generations) can be derived for each heavy neutrino individually, but it strongly depends on the mass of the lightest Standard Model neutrino and on the number of heavy neutrinos that contribute to the seesaw mechanism. Our results have implications for the perspectives of future colliders or fixed target experiments to rule out certain mass ranges for heavy neutrinos.

  • Neutrino event generators: Foundation, Status and Future

    by: Mosel, Ulrich (Giessen U.)

    Neutrino event generators are an essential tool needed for the extraction of neutrino mixing parameters, the mass hierarchy and a CP violating phase from long-baseline experiments. In this article I first describe in quite general terms the theoretical basis and the approximations needed to get to present-days generators. I also discuss the strengths and limitations of theoretical models used to describe semi-inclusive neutrino-nucleus reactions. I then confront present day's generators with this theoretical basis by detailed discussions of the various reaction processes. Finally, as examples I then show for various experiments results of the generator GiBUU for lepton semi-inclusive cross sections as well as particle spectra. I also discuss features of these cross sections in terms of the various reaction components, with predictions for DUNE. Finally, I argue for the need for a new neutrino generator that respects our present-day knowledge of both nuclear theory and nuclear reactions and is as much state-of-the-art as the experimental equipment. I outline some necessary requirements for such a new generator.

  • Neutrino nature, total and geometric phase

    by: Capolupo, Antonio (INFN, Salerno) et al.

    We study the total and the geometric phase associated with neutrino mixing and we show that the phases produced by the neutrino oscillations have different values depending on the representation of the mixing matrix and on the neutrino nature. Therefore the phases represent a possible probe to distinguish between Dirac and Majorana neutrinos.

  • Direct Detections of Dark Matter in the Presence of Non-standard Neutrino Interactions

    by: Chao, Wei (Beijing Normal U.) et al.

    In this paper we investigate impacts of non-standard neutrino interactions (NSIs) to the limitations on the discovery potential of dark matter in direct detection experiments. New neutrino floors are derived taking into account current upper bounds on the effective couplings of various NSIs. Our study shows that the neutrino floors of the standard model neutral current interactions can be significantly changed in the presence of vector-current NSI and scalar-current NSI, and the neutrino floors can be raised up to about ${\cal O}(20\%)$ in the presence of pseudo-scalar-current NSI, and there are almost no impacts to the neutrino floors from the axial-vector NSI and the tensor NSI. We suggest combining the dark matter direct detection experiments with the coherent elastic neutrino nucleus scattering experiments to hunt for new physics behind the signal of nuclear recoil in the future.

  • Flavor from the double tetrahedral group without supersymmetry: flavorful axions and neutrinos

    by: Carone, Christopher D. (William-Mary Coll.) et al.

    We extend the work of Carone, Chaurasia and Vasquez on non-supersymmetric models of flavor based on the double tetrahedral group. Three issues are addressed: (1) the sector of flavor-symmetry-breaking fields is simplified and their potential studied explicitly, (2) a flavorful axion is introduced to solve the strong CP problem and (3) the model is extended to include the neutrino sector. We show how the model can accommodate the strong hierarchies manifest in the charged fermion Yukawa matrices, while predicting a qualitatively different form for the light neutrino mass matrix that is consistent with observed neutrino mass squared differences and mixing angles.

  • Timing the Neutrino Signal of a Galactic Supernova

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

    We study several methods for timing the neutrino signal of a galactic supernova for different detectors via Monte Carlo simulations. We find that, for the methods we studied, both Hyper-Kamiokande and IceCube can reach precisions of $\sim1\,$ms for the neutrino burst, while a potential IceCube Gen2 upgrade will reach sub-ms precision. In the case of a failed SN, we find that detectors like SK and JUNO can reach precisions of $\sim0.1\,$ms while HK could potentially reach a resolution of $\sim 0.01\,$ms so that the impact of the BH formation process itself becomes relevant. Two possible applications for this are the triangulation of a (failed) SN as well as the possibility to constrain neutrino masses via a time-of-flight measurement using a potential gravitational wave signal as reference.

  • Neutrino Emission as Diagnostics of Core-Collapse Supernovae

    by: Müller, B. (Monash U.)

    With myriads of detection events from a prospective Galactic core-collapse supernova, current and future neutrino detectors will be able to sample detailed, time-dependent neutrino fluxes and spectra. This offers enormous possibilities for inferring supernova physics from the various phases of the neutrino signal from the neutronization burst through the accretion and early explosion phase to the cooling phase. The signal will constrain the time evolution of bulk parameters of the young proto-neutron star like its mass and radius as well as the structure of the progenitor, probe multi-dimensional phenomena in the supernova core, and constrain thedynamics of the early explosion phase. Aside from further astrophysical implications, supernova neutrinos may also shed further light on the properties of matter at supranuclear densities and on open problems in particle physics.

  • Phenomenology of keV scale sterile neutrino dark matter with $S_{4}$ flavor symmetry

    by: Gautam, Nayana (Tezpur U.) et al.

    We study the possibility of simultaneously addressing neutrino phenomenology and the dark matter in the framework of inverse seesaw. The model is the extension of the standard model by the addition of two right handed neutrinos and three sterile fermions which leads to a light sterile state with the mass in the keV range along with three light active neutrino states. The lightest sterile neutrino can account for a feasible dark matter(DM) candidate. We present a $S_{4}$ flavor symmetric model which is further augmented by $Z_{4}\times Z_{3}$ symmetry to constrain the Yukawa Lagrangian. The structures of the mass matrices involved in inverse seesaw within the $S_{4}$ framework naturally give rise to correct neutrino mass matrix with non-zero reactor mixing angle $ \theta_{13}$. In this framework, we conduct a detailed numerical analysis both for normal hierarchy as well as inverted hierarchy to obtain dark matter mass and DM-active mixing which are the key factors for considering sterile neutrino as a viable dark matter candidate. We constrain the parameter space of the model from the latest cosmological bounds on the mass of the dark matter and DM-active mixing.

  • Matrix norms and search for sterile neutrinos

    by: Flieger, Wojciech (Silesia U.) et al.

    Matrix norms can be used to measure the "distance" between two matrices which translates naturally to the problem of calculating the unitary deviation of the neutrino mixing matrices. Variety of matrix norms opens a possibility to measure such deviations on different structural levels of the mixing matrix.

  • Roles of sterile neutrinos in particle physics and cosmology
    Int.J.Mod.Phys. A34 (2019) 1930005

    by: Kang, Sin Kyu (Seoultech)

    The impacts of the light sterile neutrino hypothesis in particle physics and cosmology are reviewed. The observed short baseline neutrino anomalies challenging the standard explanation of neutrino oscillations within the framework of three active neutrinos are addressed. It is shown that they can be interpreted as the experimental hints pointing towards the existence of sterile neutrino at the eV scale. While the electron neutrino appearance and disappearance data are in favor of such a sterile neutrino, the muon disappearance data disfavor it, which gives rise to a strong appearance–disappearance tension. After a brief review on the cosmological effects of light sterile neutrinos, proposed signatures of light sterile neutrinos in the existing cosmological data are discussed. The keV-scale sterile neutrinos as possible dark matter candidates are also discussed by reviewing different mechanisms of how they can be produced in the early Universe and how their properties can be constrained by several cosmological observations. We give an overview of the possibility that keV-scale sterile neutrino can be a good DM candidate and play a key role in achieving low-scale leptogenesis simultaneously by introducing a model where an extra light sterile neutrino is added on top of type I seesaw model.

  • Proton decay at 1-loop
    Phys.Rev. D99 (2019) 095021

    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.

  • 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 ντ events seen in the OPERA experiment [1] in constraining the Non Standard Interaction parameter εμτ affecting neutrino propagation in matter and the allowed parameter space of models with one sterile neutrino of the 3+1 type.

  • Neutrino Masses from a Dark Neutrino Sector below the Electroweak Scale
    Phys.Rev. D99 (2019) 091701

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

    We consider a minimal extension of the Standard Model which advocates a dark neutrino sector charged under a hidden U(1)′. We show that neutrino masses can arise radiatively in this model. The observed values are compatible with a light dark sector below the electroweak scale and would imply new heavy fermions which may be testable in the next generation of beam dump searches at DUNE, NA62 and SHIP.

  • Constraining dark matter-neutrino interactions with IceCube-170922A
    Phys.Rev. D99 (2019) 083018

    by: Choi, Ki-Young (Sungkyunkwan U.) et al.

    Astrophysical neutrinos travel long distances from their sources to the Earth traversing dark matter halos of clusters of galaxies and that of our own Milky Way. The interaction of neutrinos with dark matter may affect the flux of neutrinos. The recent multimessenger observation of a high energy neutrino, IceCube-170922A, can give a robust upper bound σ/Mdm≲5.1×10-23  cm2/GeV on the interaction between neutrino and dark matter at a neutrino energy of 290 TeV allowing 90% suppression. Combining the constraints from cosmic microwave background and Large Scale Structure at different neutrino energies, we can constrain models of dark matter-neutrino interactions.

  • Predicting neutrino oscillations with “bi-large” lepton mixing matrices
    Phys.Lett. B792 (2019) 461-464

    by: Chen, Peng (Zhejiang Ocean U.) et al.

    We propose two schemes for the lepton mixing matrix $U = U_l^\dagger U_\nu$, where $U = U_l$ refers to the charged sector, and $U_\nu$ denotes the neutrino diagonalization matrix. We assume $U_\nu$ to be CP conserving and its three angles to be connected with the Cabibbo angle in a simple manner. CP violation arises solely from the $U_l$, assumed to have the CKM form, $U_l\simeq V_{\rm CKM}$, suggested by unification. Oscillation parameters depend on a single parameter, leading to narrow ranges for the "solar" and "accelerator" angles $\theta_{12}$ and $\theta_{23}$, as well as for the CP phase, predicted as $\delta_{\rm CP}\sim 1.3\pi$.

  • Natural quark mixing and inverse seesaw in a left-right model with an axion
    JHEP 1905 (2019) 078

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

    We consider a minimal left-right model with a Peccei-Quinn symmetry, where generalised charge conjugation plays the role of the left-right symmetry. We show how the spontaneous breaking of the Peccei-Quinn symmetry by a scalar singlet can provide us with solutions not only to the strong CP and dark matter problems but can also help to generate naturally suppressed off-diagonal CKM elements and small neutrino masses via the inverse seesaw mechanism. For this, we make use of an economical scalar sector composed of a bi-doublet, two doublets and a singlet only. As a result of the new gauge bosons and neutrinos, the neutrinoless double beta decay, as well as lepton flavour violating processes, receives new contributions which can, in principle, become relevant due to the low-scale nature of the inverse seesaw mechanism. The model can easily accommodate all the current data on fermion masses and mixing even if the left-right scale is only high enough to evade the current experimental constraints.

  • Simplest Radiative Dirac Neutrino Mass Models
    Nucl.Phys. B (2019) 114636

    by: Saad, Shaikh (Oklahoma State U.)

    If neutrinos are Dirac particles, their right-handed partners must be present in the theory. Once introduced in the Standard Model (SM), the difference between the baryon number B and the lepton number L can be promoted to a local U(1)B−L symmetry since the corresponding gauge anomalies can be canceled by the right-handed neutrinos. Furthermore, the extremely small neutrino mass can be explained naturally if it is originated from the quantum correction. In this work, we propose simplest models of radiative Dirac neutrino mass using only U(1)B−L symmetry, and without introducing additional fermions and without imposing ad hoc symmetries. In this simple framework, we provide minimal models where Dirac neutrino mass appears at the (i) one-loop, (ii) two-loop and (iii) three-loop. By performing systematic analysis, we show that the minimal one-loop model requires three beyond SM scalar multiplets, whereas minimal two-loop and three-loop models require five. The presented two-loop and three-loop Dirac mass models have not appeared in the literature before.

  • Observational status of the Galileon model general solution from cosmological data and gravitational waves
    JCAP 2019 (2019) 011

    by: Leloup, C. (IRFU, Saclay) et al.

    The Galileon model is a tensor-scalar theory of gravity which explains the late acceleration of the Universe expansion with no instabilities and recovers General Relativity in the strong field limit. Most constraints obtained so far on Galileon model parameters from cosmological data were derived for the limited subset of tracker solutions and reported tensions between the model and data. This paper presents the first exploration of the general solution of the Galileon model, which is confronted against recent cosmological data for both background observables and linear perturbations, using Monte-Carlo Markov chains. As representative scenarios of the Galileon models, we study the full Galileon model with disformal coupling to matter and the uncoupled cubic Galileon model. We find that the general solution of the full Galileon model provides a good fit to CMB spectra, while the cubic Galileon model does not. When extending the comparison to BAO and SNIa data, even the general solution of the full Galileon model fails at providing a good fit to all datasets simultaneously. Tensions remain if the models are extended with an additional free parameter, such as the sum of active neutrino masses or the normalization of the CMB lensing spectrum. Finally, the multi-messenger observation of GW170817 is also discussed in the framework of the scenarios considered. The time delay between the gravitational signal and its electromagnetic counterpart was computed \textit{a posteriori} in every scenario of the full Galileon model cosmological fit chains and found to be ruled out by this observation.

  • A Dark Matter Interpretation of the ANITA Anomalous Events
    Phys.Rev. D99 (2019) 095014

    by: Heurtier, Lucien (Arizona U.) et al.

    The ANITA collaboration recently reported the detection of two anomalous upward-propagating extensive air showers exiting the Earth with relatively large emergence angles and energies in the range O(0.5–1)  EeV. We interpret these two events as coming from the decay of a massive dark matter candidate (mDM≳109  GeV) decaying into a pair of right-handed neutrinos. While propagating through the Earth, these extremely boosted decay products convert eventually to τ-leptons which lose energy during their propagation and produce showers in the atmosphere detectable by ANITA at emergence angles larger than what Standard Model neutrinos could ever produce. We performed Monte Carlo simulations to estimate the propagation and energy loss effects and derived differential effective areas and number of events for the ANITA and the IceCube detectors. Interestingly, the expected number of events for IceCube is of the very same order of magnitude as the number of events observed by ANITA but at larger emergence angles, and energies ≲0.1  EeV. Such features match perfectly with the presence of the two upward-going events IceCube-140109 and IceCube-121205 that have been exhibited from a recent reanalysis of IceCube data samples.

  • GUT inspired $SO(5) \times U(1) \times SU(3)$ gauge-Higgs unification
    OU-HET 989
    Phys.Rev. D99 (2019) 095010

    by: Funatsu, Shuichiro (CCNU, Wuhan, Inst. Part. Phys.) et al.

    An SO(5)×U(1)×SU(3) gauge-Higgs unification model inspired by SO(11) gauge-Higgs grand unification is constructed in the Randall-Sundrum warped space. The 4D Higgs boson is identified with the Aharonov-Bohm phase in the fifth dimension. Fermion multiplets are introduced in the bulk in the spinor, vector and singlet representations of SO(5) such that they are implemented in the spinor and vector representations of SO(11). The mass spectrum of quarks and leptons in three generations is reproduced except for the down-quark mass. The small neutrino masses are explained by the gauge-Higgs seesaw mechanism which takes the same form as in the inverse seesaw mechanism in grand unified theories in four dimensions.

  • Leggett-Garg inequality in the context of three flavour neutrino oscillation
    Phys.Rev. D99 (2019) 095001

    by: Naikoo, Javid (IIT, Jodhpur) et al.

    The present work is devoted to the characterization of the Leggett-Garg inequality (LGI) for three flavored neutrino oscillations in the presence of both matter and charge-conjugation and parity violating effects. This study complements and completes the recent one put forward in arXiv:1710.05562 by relaxing the stationary condition. At variance with the latter case, the LGI contains interference terms which cannot be expressed in terms of experimentally measurable quantities, thus drawing a clear-cut distinction between the two scenarios, as well as highlighting the role of the stationary assumption on such systems. We find that the additional terms are small for a high energy neutrino beam compared to the maximum value attained by the Leggett-Garg parameter.

  • Analytical solutions to renormalization-group equations of effective neutrino masses and mixing parameters in matter
    JHEP 1905 (2019) 035

    by: Wang, Xin (Beijing, Inst. High Energy Phys.) et al.

    Recently, a complete set of differential equations for the effective neutrino masses and mixing parameters in matter have been derived to characterize their evolution with respect to the ordinary matter term $a \equiv 2\sqrt{2}G^{}_{\rm F} N^{}_e E$, in analogy with the renormalization-group equations (RGEs) for running parameters. Via series expansion in terms of the small ratio $\alpha^{}_{\rm c} \equiv \Delta^{}_{21}/\Delta^{}_{\rm c}$, we obtain approximate analytical solutions to the RGEs of the effective neutrino parameters and make several interesting observations. First, at the leading order, $\widetilde{\theta}^{}_{12}$ and $\widetilde{\theta}^{}_{13}$ are given by the simple formulas in the two-flavor mixing limit, while $\widetilde{\theta}^{}_{23} \approx \theta^{}_{23}$ and $\widetilde{\delta} \approx \delta$ are not changed by matter effects. Second, the ratio of the matter-corrected Jarlskog invariant $\widetilde{\cal J}$ to its counterpart in vacuum ${\cal J}$ approximates to $\widetilde{\cal J}/{\cal J} \approx 1/(\widehat{C}^{}_{12} \widehat{C}^{}_{13})$, where $\widehat{C}^{}_{12} \equiv \sqrt{1 - 2 A^{}_* \cos 2\theta^{}_{12} + A^2_*}$ with $A^{}_* \equiv a/\Delta^{}_{21}$ and $\widehat{C}^{}_{13} \equiv \sqrt{1 - 2 A^{}_{\rm c} \cos 2\theta^{}_{13} + A^2_{\rm c}}$ with $A^{}_{\rm c} \equiv a/\Delta^{}_{\rm c}$. Finally, after taking higher-order corrections into account, we find compact and simple expressions of all the effective parameters.

  • Scotogenic $U(1)_\chi$ Dirac Neutrinos
    Phys.Lett. B793 (2019) 411-414

    by: Ma, Ernest (UC, Riverside)

    The standard model of quarks and leptons is extended to include the gauge symmetry $U(1)_\chi$ which comes from $SO(10) \to SU(5) \times U(1)_\chi$. The radiative generation of Dirac neutrino masses through dark matter is discussed in two examples. One allows for light Dirac fermion dark matter. The other allows for self-interacting scalar dark matter with a light scalar mediator which decays only to two neutrinos.

  • Identification of nuclear effects in neutrino and antineutrino interactions on nuclei using generalized final-state correlations
    Phys.Rev. C99 (2019) 055504

    by: Lu, Xianguo (Oxford U.) et al.

    In the study of neutrino and antineutrino interactions in the GeV regime, kinematic imbalances of the final-state particles have sensitivities to different nuclear effects. Previous ideas based on neutrino quasielastic interactions [Phys. Rev. C94, 015503 (2016), Phys. Rev. C95, 065501 (2017)] are now generalized to antineutrino quasielastic interactions, as well as neutrino and antineutrino pion productions. Measurements of these generalized final-state correlations could provide unique and direct constraints on the nuclear response inherently different for neutrinos and antineutrinos, and therefore delineate effects that could mimic charge-parity violation in neutrino oscillations.

  • How to relax the cosmological neutrino mass bound
    JCAP 2019 (2020) 049

    by: Oldengott, Isabel M. (Valencia U.) et al.

    We study the impact of non-standard momentum distributions of cosmic neutrinos on the anisotropy spectrum of the cosmic microwave background and the matter power spectrum of the large scale structure. We show that the neutrino distribution has almost no unique observable imprint, as it is almost entirely degenerate with the effective number of neutrino flavours, Neff, and the neutrino mass, mν. Performing a Markov chain Monte Carlo analysis with current cosmological data, we demonstrate that the neutrino mass bound heavily depends on the assumed momentum distribution of relic neutrinos. The message of this work is simple and has to our knowledge not been pointed out clearly before: cosmology allows that neutrinos have larger masses if their average momentum is larger than that of a perfectly thermal distribution. Here we provide an example in which the mass limits are relaxed by a factor of two.

  • Flavor constraints on electroweak ALP couplings
    Eur.Phys.J. C79 (2019) 369

    by: Gavela, M.B. (Madrid, IFT) et al.

    We explore the signals of axion-like particles (ALPs) in flavor-changing neutral current (FCNC) processes. The most general effective linear Lagrangian for ALP couplings to the electroweak bosonic sector is considered, and its contribution to FCNC decays is computed up to one-loop order. The interplay between the different couplings opens new territory for experimental exploration, as analyzed here in the ALP mass range $0
  • Trimaximal Neutrino Mixing from Modular A4 Invariance with Residual Symmetries
    SISSA 57/2018/FISI
    Phys.Lett. B793 (2019) 247-258

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

    We construct phenomenologically viable models of lepton masses and mixing based on modular A4 invariance broken to residual symmetries Z3T or Z3ST and Z2S respectively in the charged lepton and neutrino sectors. In these models the neutrino mixing matrix is of trimaximal mixing form. In addition to successfully describing the charged lepton masses, neutrino mass-squared differences and the atmospheric and reactor neutrino mixing angles θ23 and θ13 , 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 the existence of specific correlations between i) the values of the solar neutrino mixing angle θ12 and the angle θ13 (which determines θ12 ), ii) the values of the Dirac CPV phase δ and of the angles θ23 and θ13 , iii) the sum of the neutrino masses and θ23 , iv) the neutrinoless double beta decay effective Majorana mass and θ23 , and v) between the two Majorana phases.

  • Singlet-doublet fermion and triplet scalar dark matter with radiative neutrino masses
    JHEP 1905 (2019) 015

    by: Fiaschi, Juri (Munster U., ITP) et al.

    We present a detailed study of a combined singlet-doublet fermion and triplet scalar model for dark matter. These models have only been studied separately in the past. Together, they form a simple extension of the Standard Model that can account for dark matter and explain the existence of neutrino masses, which are generated radiatively. This holds even if singlet-doublet fermions and triplet scalars never contribute simultaneously to the dark matter abundance. However, this also implies the existence of lepton flavour violating processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new $\mathbb{Z}_2$ symmetry to stabilise the dark matter candidate. We analyse the dark matter, neutrino mass and lepton flavour violation aspects both separately and in conjunction, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and lepton flavour violation constraints. We find that dark matter in this model is fermionic for masses below about 1 TeV and scalar above. The narrow mass regions found previously for the two separate models are enlarged by their coupling. While coannihilations of the weak isospin partners are sizeable, this is not the case for fermions and scalars despite their often similar masses due to the relatively small coupling of the two sectors, imposed by the small neutrino masses. We observe a high degree of complementarity between direct detection and lepton flavour violation experiments, which should soon allow to fully probe the fermionic dark matter sector and at least partially the scalar dark matter sector.

  • Testing of quasi-elastic neutrino charged-current and two-body meson exchange current models with the MiniBooNE neutrino data and analysis of these processes at energies available at the NOvA experiment
    Phys.Rev. D99 (2019) 093001

    by: Butkevich, A.V.
    The charged-current quasi-elastic scattering of muon neutrinos on a carbon target is analyzed using the relativistic distorted-wave impulse approximation (RDWIA), taking into account the contribution of the two-particle and two-hole meson exchange current (MEC) to the weak response functions. A fit the RDWIA+MEC model to the MiniBooNE neutrino data is performed, and the best-fit value of nucleon axial mass MA≈1.20  GeV is obtained. We also extract the values of the axial form factor FA(Q2) as a function of the squared momentum transfer Q2 from the measured dσ/dQ2 cross section. The flux-integrated charged-current quasi-elastic–like differential cross sections for neutrino scattering at energies of the NOvA experiment are estimated within the RDWIA+MEC approach.

  • Assessing the sensitivity of PINGU to effective dark matter-nucleon interactions
    JCAP 2019 (2019) 023

    by: Bäckström, Anton (Chalmers U. Tech.) et al.

    We calculate the sensitivity of next generation neutrino telescopes to the 28 (isoscalar and isovector) coupling constants defining the non-relativistic effective theory of (spin 1/2) dark matter (DM)-nucleon interactions. We take as a benchmark detector the proposed Precision IceCube Next Generation Upgrade (PINGU), although our results are valid for any other neutrino telescope of similar effective volume. We express PINGU's sensitivity in terms of $5\sigma$ sensitivity contours in the DM-mass - coupling constant plane, and compare our sensitivity contours with the 90% C.L. exclusion limits on the same coupling constants that we obtain from a reanalysis of the null result of current DM searches at IceCube/DeepCore. We find that PINGU can effectively probe not only the canonical spin-independent and spin-dependent DM-nucleon interactions, but also velocity-dependent or momentum-dependent interactions that generate coherently enhanced DM-nucleus scattering cross sections. We also find that PINGU's $5\sigma$ sensitivity contours are significantly below current IceCube/DeepCore 90% C.L. exclusion limits when $b\bar{b}$ is the leading DM annihilation channel. This result shows the importance of lowering the experimental energy threshold when probing models that generate soft neutrino energy spectra, and holds true independently of the assumed DM-nucleon interaction and for all DM masses tested here. When DM primarily annihilates into $\tau\bar{\tau}$, a PINGU-like detector will improve upon current exclusion limits for DM masses below $35$ GeV, independently of the assumed DM-nucleon interaction.

  • Representing seesaw neutrino models and their motion in lepton flavour space
    JHEP 1905 (2019) 011

    by: Di Bari, Pasquale (Southampton U.) et al.

    We discuss how seesaw neutrino models can be graphically represented in lepton flavour space. We examine various popular models and show how this representation helps understanding their properties and connection with experimental data showing in particular how certain texture zero models are ruled out. We also introduce a new matrix, the bridging matrix, that brings from the light to the heavy neutrino mass flavour basis, showing how this is related to the orthogonal matrix and how different quantities are easily expressed through it. We then show how one can randomly generate orthogonal and leptonic mixing matrices uniformly covering all flavour space in an unbiased way (Haar-distributed matrices). Using the isomorphism between the group of complex rotations and the Lorentz group, we also introduce the concept of Lorentz boost in flavour space for a seesaw model and how this has an insightful physical interpretation. Finally, as a significant application, we consider N$_{2}$-leptogenesis. Using current experimental values of low energy neutrino parameters, we show that the probability that at least one flavoured decay parameter of the lightest right-handed neutrino is smaller than unity is about 49% (to be compared with the tiny probability that the total decay parameter is smaller than unity, P (K$_{I}$< 1) ∼ 0.1%, confirming the crucial role played by flavour effects). On the other hand when m$_{1}$ ≳ 0.1 eV this probability reduces to less than 5%, showing how also N$_{2}$-leptogenesis disfavours degenerate light neutrinos.

  • WIMP dark matter in the parity solution to the strong CP problem
    JHEP 1904 (2019) 162

    by: Kawamura, Junichiro (Ohio State U.) et al.

    We extend the Standard Model (SM) with parity symmetry, motivated by the strong CP problem and dark matter. In our model, parity symmetry is conserved at high energy by introducing a mirror sector with the extra gauge symmetry, SU(2)$_{R}$ × U(1)$_{R}$. The charges of SU(2)$_{R}$ × U(1)$_{R}$ are assigned to the mirror fields in the same way as in the SM, but the chiralities of the mirror fermions are opposite to respect the parity symmetry. The strong CP problem is resolved, since the mirror quarks are also charged under the SU(3)$_{c}$ in the SM. In the minimal setup, the mirror gauge symmetry leads to stable colored particles which would be inconsistent with the observed data, so that we introduce two scalars in order to deplete the stable colored particles. Interestingly, one of the scalars becomes stable because of the gauge symmetry and therefore can be a good dark matter candidate. We especially study the phenomenology relevant to the dark matter, i.e. thermal relic density, direct and indirect searches for the dark matter. The bounds from the LHC experiment and the Landau pole are also taken into account. As a result, we find that a limited region is viable: the mirror up quark mass is around [600 GeV, 3 TeV] and the relative mass difference between the dark matter and the mirror up quark or electron is about $ \mathcal{O} $ (1–10%). We also discuss the neutrino sector and show that the right-handed neutrinos in the mirror sector can increase the effective number of neutrinos or dark radiation by 0.14.

  • Event generation for beam dump experiments
    JHEP 1905 (2019) 028

    by: Buonocore, Luca (Zurich U.) et al.

    A wealth of new physics models which are motivated by questions such as the nature of dark matter, the origin of the neutrino masses and the baryon asymmetry in the universe, predict the existence of hidden sectors featuring new particles. Among the possibilities are heavy neutral leptons, vectors and scalars, that feebly interact with the Standard Model (SM) sector and are typically light and long lived. Such new states could be produced in high-intensity facilities, the so-called beam dump experiments, either directly in the hard interaction or as a decay product of heavier mesons. They could then decay back to the SM or to hidden sector particles, giving rise to peculiar decay or interaction signatures in a far-placed detector. Simulating such kind of events presents a challenge, as not only short-distance new physics (hard production, hadron decays, and interaction with the detector) and usual SM phenomena need to be described but also the geometry of the detector has to be taken into account for a reliable estimate of the event yield and distributions. In this work, we describe a new plugin to the MadGraph5_aMC@NLO platform, which allows the complete simulation of new physics processes relevant for beam dump experiments, including the various mechanisms for the production of hidden particles, namely their decays or scattering off SM particles, as well as their far detection, keeping into account spatial correlations and the geometry of the experiment.

  • Neutrino damping in a fermion and scalar background
    Phys.Rev. D99 (2019) 095013

    by: Nieves, José F. (Puerto Rico U., Rio Piedras) et al.

    We consider the propagation of a neutrino in a background composed of a scalar particle and a fermion using a simple model for the coupling of the form λf¯RνLϕ. In the presence of these interactions there can be damping terms in the neutrino effective potential and index of refraction. We calculate the imaginary part of the neutrino self-energy in this case, from which the damping terms are determined. The results are useful in the context of dark matter-neutrino interaction models in which the scalar and/or fermion constitute the dark matter. The corresponding formulas for models in which the scalar particle couples to two neutrinos via a coupling of the form λ(ννϕ)ν¯RcνLϕ are then obtained as a special case, which can be important also in the context of neutrino collective oscillations in a supernova and in the early Universe hot plasma before neutrino decoupling. A particular feature of our results is that the damping term in a νϕ background is independent of the antineutrino-neutrino asymmetry in the background. Therefore, the relative importance of the damping term may be more significant if the neutrino-antineutrino asymmetry in the background is small, because the leading Z-exchange and ϕ-exchange contributions to the effective potential, which are proportional to the neutrino-antineutrino asymmetry, are suppressed in that case, while the damping term is not.

  • Monochromatic dark neutrinos and boosted dark matter in noble liquid direct detection
    Phys.Rev. D99 (2019) 103003

    by: McKeen, David (TRIUMF) et al.

    If dark matter self-annihilates into neutrinos or a second component of (“boosted”) dark matter that is nucleophilic, the annihilation products may be detected with high rates via coherent nuclear scattering. A future multi-ten-tonne liquid xenon detector such as DARWIN, and a multi-hundred-tonne liquid argon detector, argo, would be sensitive to the flux of these particles in complementary ranges of 10–1000 MeV dark matter masses. We derive these sensitivities after accounting for atmospheric and diffuse supernova neutrino backgrounds, and realistic nuclear recoil acceptances. We find that their constraints on the dark neutrino flux may surpass neutrino detectors such as Super-Kamiokande, and that they would extensively probe parametric regions that explain the missing satellites problem in neutrino portal models. The XENON1T and Borexino experiments currently restrict the effective baryonic coupling of thermal boosted dark matter to ≲10–100× the weak interaction, but darwin and argo would probe down to couplings 10 times smaller. Detection of boosted dark matter with baryonic couplings ∼10-3–10-2× the weak coupling could indicate that the dark matter density profile in the centers of galactic halos become cored, rather than cuspy, through annihilations. This work demonstrates that, alongside liquid xenon, liquid argon direct detection technology would emerge a major player in dark matter searches within and beyond the wimp paradigm.

  • Low energy neutrinos from stopped muons in the Earth
    Phys.Rev. D99 (2019) 073007

    by: Guo, Wan-Lei (Beijing, Inst. High Energy Phys.)

    We explore the low energy neutrinos from stopped cosmic ray muons in the Earth. Based on the muon intensity at the sea level and the muon energy loss rate, the depth distributions of stopped muons in the rock and sea water can be derived. Then we estimate the μ- decay and nuclear capture probabilities in the rock. Finally, we calculate the low energy neutrino fluxes and find that they depend heavily on the detector depth d. For d=1000  m, the νe, ν¯e, νμ, and ν¯μ fluxes in the range of 13  MeV≤Eν≤53  MeV are averagely 10.8%, 6.3%, 3.7%, and 6.2% of the corresponding atmospheric neutrino fluxes, respectively. The above results will be increased by a factor of 1.4 if the detector depth d<30  m. In addition, we find that most neutrinos come from the region within 200 km and the near horizontal direction, and the ν¯e flux depends on the local rock and water distributions.

  • Modular A$_{5}$ symmetry for flavour model building
    SISSA 54/2018/FISI
    JHEP 1904 (2019) 174

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

    In the framework of the modular symmetry approach to lepton flavour, we consider a class of theories where matter superfields transform in representations of the finite modular group $\Gamma_5 \simeq A_5$. We explicitly construct a basis for the 11 modular forms of weight 2 and level 5. We show how these forms arrange themselves into two triplets and a quintet of $A_5$. We also present multiplets of modular forms of higher weight. Finally, we provide an example of application of our results, constructing two models of neutrino masses and mixing based on the supersymmetric Weinberg operator.

  • Leptoquark solution for both the flavor and ANITA anomalies
    Phys.Rev. D99 (2019) 095018

    by: Chauhan, Bhavesh (Ahmedabad, Phys. Res. Lab) et al.

    The ANITA experiment has seen anomalous Earth emergent showers of EeV energies which cannot be explained with Standard Model interactions. In addition, tests of lepton flavor universality in R(D(*)) and R(K(*)) have shown significant deviations from theoretical predictions. It is known that, among single leptoquark solutions, only the chiral vector leptoquark U1∼(3,1,2/3) can simultaneously address the discrepancies. In this paper, we show that the leptoquark motivated by flavor anomalies coupled to a sterile neutrino can also explain the ANITA anomalous events. We consider two scenarios, (a) the sterile neutrino, produced via resonant leptoquark mediated neutrino-nucleon interactions, propagates through the Earth without significant attenuation and decays near the surface to a τ lepton; and (b) a cosmogenic sterile neutrino interacts with the matter near the surface of Earth and generates a τ lepton. These two scenarios give significantly large survival probabilities even when regeneration effects are not taken into account. In the second scenario, the distribution of emergent tau energy peaks in the same energy range as seen by ANITA.

  • Lepton mixing predictions from $S_4$ in the tridirect CP approach to two right-handed neutrino models
    Phys.Rev. D99 (2019) 075035

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

    We perform an exhaustive analysis of all possible breaking patterns arising from S4⋊HCP in a new tridirect CP approach to the minimal seesaw model with two right-handed neutrinos, and construct a realistic flavor model along these lines. According to this approach, separate residual flavor and CP symmetries persist in the charged lepton, “atmospheric” and “solar” right-handed neutrino sectors, i.e., we have three symmetry sectors rather than the usual two of the semidirect CP approach (charged leptons and neutrinos). Following the tridirect CP approach, we find 26 kinds of independent phenomenologically interesting mixing patterns. Eight of them predict a normal ordering (NO) neutrino mass spectrum and the other 18 predict an inverted ordering (IO) neutrino mass spectrum. For each phenomenologically interesting mixing pattern, the corresponding predictions for the Pontecorvo-Maki-Nakagawa-Sakata matrix, the lepton mixing parameters, the neutrino masses and the effective mass in neutrinoless double beta decay are given in a model-independent way. One breaking pattern with an NO spectrum and two breaking patterns with IO spectra correspond to form dominance. We find that the lepton mixing matrices of three kinds of breaking patterns with NO spectra and one form dominance breaking pattern with an IO spectrum preserve the first column of the tribimaximal mixing matrix, i.e., yield a TM1 mixing matrix.

  • Neutrinoless Double Beta Decay with Non-standard Majoron Emission
    Phys.Rev.Lett. 122 (2019) 181801

    by: Cepedello, Ricardo (Valencia U., IFIC) et al.

    We present a novel mode of neutrinoless double-β decay with emission of a light Majoron-like scalar particle ϕ. We assume it couples via an effective seven-dimensional operator with a (V+A) lepton current and (V±A) quark currents leading to a long-range contribution that is unsuppressed by the light neutrino mass. We calculate the total double-β decay rate and determine the fully differential shape for this mode. We find that future double-β decay searches are sensitive to scales of the order ΛNP≈1  TeV for the effective operator and a light scalar mϕ<0.2  MeV, based on ordinary double-β decay Majoron searches. The angular and energy distributions can deviate considerably from that of two-neutrino double-β decay, which is the main background. We point out possible ultraviolet completions where such an effective operator can emerge.

  • Light Dark Matter at Neutrino Experiments
    Phys.Rev.Lett. 122 (2019) 181802

    by: Ema, Yohei (DESY) et al.

    Sub-GeV dark matter particles up-scattered by cosmic rays gain enough kinetic energy to pass the thresholds of large volume detectors on Earth. We then use public Super-Kamiokande and MiniBooNE data to derive a novel limit on the scattering cross section of dark matter with electrons that extends down to sub-keV masses, closing a previously allowed wide region of parameter space. We finally discuss search strategies and prospects at existing and planned neutrino facilities.

  • R-parity from string compactification
    Phys.Rev. D99 (2019) 093004

    by: Kim, Jihn E. (Kyung Hee U.)

    In this paper, we embed the Z4R parity as a discrete subgroup of a global symmetry U(1)R obtained from Z12-I compactification of a heterotic string E8×E8′. A part of U(1)R transformation is the shift of the anticommuting variable ϑ to eiαϑ, which necessarily incorporates the transformation of the internal space coordinate. Out of six internal spaces, we identify three U(1)’s whose charges are denoted as Q18, Q20, and Q22. The U(1)R is defined as U(1)EE×U(1)KK, where U(1)EE is the part from the E8×E8′ and U(1)KK is the part generated by Q18, Q20, and Q22. We propose a method to define a U(1)R direction. The needed vacuum expectation values for breaking gauge U(1)’s except for U(1)Y of the standard model carry a U(1)R charge 4 modulo 4 such that U(1)R is broken down to Z4R at the grand unification scale. Z4R is broken to Z2R between the intermediate (∼1011  GeV) and the electroweak scales (100  GeV∼1  TeV). The conditions we impose are proton longevity, a large top quark mass, and acceptable magnitudes for the μ term and neutrino masses.

  • Novel direct detection constraints on light dark matter
    Phys.Rev.Lett. 122 (2019) 171801

    by: Bringmann, Torsten (Oslo U.) et al.

    All attempts to directly detect particle dark matter (DM) scattering on nuclei suffer from the partial or total loss of sensitivity for DM masses in the GeV range or below. We derive novel constraints from the inevitable existence of a subdominant, but highly energetic, component of DM generated through collisions with cosmic rays. Subsequent scattering inside conventional DM detectors, as well as neutrino detectors sensitive to nuclear recoils, limits the DM-nucleon scattering cross section to be below 10-31  cm2 for both spin-independent and spin-dependent scattering of light DM.

  • Measuring Relic Abundance of Minimal Dark Matter at Hadron Colliders
    Sci.China Phys.Mech.Astron. 62 (2019) 981011

    by: Cao, Qing-Hong (Peking U.) et al.

    We consider the special case that the dark matter (DM) candidate is not detected in direct-detection programs when the experimental sensitivity reaches the neutrino flux background. In such circumstance the DM searches at the colliders impose constraints on the DM relic abundance if the DM candidate is a WIMPs type. Specifically, we consider the triplet (quintet and septet) DMs in the framework of minimal DM model and explore the potential of discovering the DM candidate in the mono-jet, mono-photon and vector boson fusion channels at the Large Hadron Collider and future 100~TeV hadron collider. If the DM candidate in such a scenario is discovered at the LHC, then additional DM candidates are needed to explain the observed relic abundance. On the other hand, null results in those DM searching programs at the colliders give rise to lower limits of DM relic abundance.

  • Forecast on lepton asymmetry from future CMB experiments
    Mon.Not.Roy.Astron.Soc. 485 (2019) 2486-2491

    by: Bonilla, Alexander (Juiz de Fora U.) et al.

    We consider a cosmological lepton asymmetry in the form of neutrinos and impose new expected sensitivities on such asymmetry through the degeneracy parameter ($\xi_{\nu}$) by using some future CMB experiment configurations, such as CORE and CMB-S4. Taking the default scenario with three neutrino states, we find $\xi_{\mu} = 0.05 \pm 0.10 \, (\pm \, 0.04)$, from CORE (CMB-S4) at 95 percent CL, respectively. Also, within this scenario, we evaluate the neutrino mass scale, obtaining that the normal hierarchy mass scheme is privileged. Our results are an update concerning on the cosmological lepton asymmetry and the neutrino mass scale within this context, from which can bring a perspective on the null hypothesis for $\xi_{\nu}$ (and its effects on $\Delta N_{\rm eff}$), where perhaps, \textbf{$\xi_{\nu}$} may take a non-null value up to 95 percent CL from future experiments such as CMB-S4. Sensitivity results for CMB-S4 obtained here not including all expected systematic errors.

  • Inverse seesaw model with large $SU(2)_L$ multiplets and natural mass hierarchy
    APCTP Pre2018 - 014
    Phys.Lett. B792 (2019) 424-429

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

    We propose an inverse seesaw model with large $SU(2)_L$ multiplet fields which realizes natural mass hierarchies among neutral fermions. Here, lighter neutral fermion mass matrices are induced via two suppression mechanisms; one is small vacuum expectation value of $SU(2)_L$ triplet required by rho parameter constraint and the other is generation of Majorana mass term of extra singlet fermions at one-loop level. To realize the loop masses, we impose $Z_2$ symmetry which also guarantees stability of a dark matter candidate. Furthermore, we discuss anomalous magnetic moment and collider physics from interactions of large multiplet fields.

  • Massive Majorons and constraints on the Majoron-neutrino coupling
    DO-TH 18/23
    Phys.Rev. D99 (2019) 096005

    by: Brune, Tim (Dortmund U.) et al.

    We revisit a singlet Majoron model in which neutrino masses arise from the spontaneous violation of lepton number. If the Majoron obtains a mass of order MeV, it can play the role of dark matter. We discuss constraints on the couplings of the massive Majoron with masses of order MeV to neutrinos from supernova data. In the dense supernova core, Majoron-emitting neutrino annihilations are allowed and can change the signal of a supernova. Based on the observation of SN1987A, we exclude a large range of couplings from the luminosity and the deleptonization arguments, taking the effect of the background medium into account. If the Majoron mass does not exceed the Q-value of the experiment, the neutrino-Majoron couplings allow for neutrinoless double beta decay with Majoron emission. We derive constraints on the couplings for a Majoron mass of order MeV based on the phase space suppression and the diminishing signal-to-background ratio due to the Majoron mass. The combination of constraints from astrophysics and laboratory experiments excludes a large range of neutrino-Majoron couplings in the mass range of interest for Majoron dark matter, where they complement existing cosmological bounds from dark matter stability and the effects of a decaying Majoron on the cosmic microwave background anisotropy spectrum.

  • 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.

  • Further study on the textures of neutrino mass matrix for maximal atmospherical mixing angle and Dirac CP phase
    Phys.Rev. D99 (2019) 075034

    by: Liu, Zhi-Cheng (Liaoning Normal U.) et al.

    In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead to maximal atmospherical mixing angle (θ23=π/4) and Dirac CP phase (δ=-π/2) in two phenomenologically appealing scenarios: (1) one neutrino mass matrix element vanishing (2) one neutrino mass vanishing. For the obtained textures, some neutrino mass sum rules that relate the neutrino masses and mixing parameters emerge. With the help of these sum rules, the unknown absolute neutrino mass scale and Majorana CP phases can be determined. Some discussions about the possible textures of neutrino mass matrix that can lead to θ23=π/4, δ=-π/2 and maximal Majorana CP phases (ρ, σ=π/4 or 3π/4) as well as the model realization and breakings of the obtained textures are also given.

  • Decoherence in neutrino oscillations, neutrino nature and CPT violation
    Phys.Lett. B792 (2019) 298-303

    by: Capolupo, A. (Salerno U.) et al.

    We analyze many aspects of the phenomenon of the decoherence for neutrinos propagating in long baseline experiments. We show that, in the presence of an off-diagonal term in the dissipative matrix, the Majorana neutrino can violate the CPT symmetry, which, on the contrary, is preserved for Dirac neutrinos. We show that oscillation formulas for Majorana neutrinos depend on the choice of the mixing matrix U . Indeed, different choices of U lead to different oscillation formulas. Moreover, we study the possibility to reveal the differences between Dirac and Majorana neutrinos in the oscillations. We use the present values of the experimental parameters in order to relate our theoretical proposal with experiments.

  • 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.

  • A Model of Neutrino Mass, Baryon Asymmetry, and Asymmetric Dark Matter with $SU(2)_D\otimes U(1)_{D'}$ Dark Sector
    Nucl.Phys. B (2019) 114643

    by: Yang, Wei-Min (Hefei, CUST)

    I suggest a new extension of the standard model of particle physics, which introduces a dark sector with the $SU(2)_{D}\otimes U(1)_{D'}$ symmetry besides the SM sector. The new particles of the model all inhabit in the dark sector. The dark gauge symmetry breaking will bring about fruitful physics beyond the SM. The tiny neutrino mass is generated through the Dirac-type seesaw mechanism. The inflaton decay can not only provide the universe inflation and reheating, but also lead to the baryon asymmetry and the asymmetric cold dark matter. In short, the model provides an unification of the neutrino mass, the baryon asymmetry, the asymmetric CDM and the inflation, and it can account for their common origin. Finally, it is very possible to test the model predictions and probe the dark sector physics in near future experiments.

  • Prospects of indirect searches for dark matter annihilations in the earth with ICAL@INO
    JHEP 1905 (2019) 039

    by: Tiwari, Deepak (HBNI, Mumbai) et al.

    We study the prospects of detecting muon events at the upcoming Iron CALorimeter (ICAL) detector to be built at the proposed India-based Neutrino Observatory (INO) facility due to neutrinos arising out of annihilation of Weakly Interactive Massive Particles (WIMP) in the centre of the earth. The atmospheric neutrinos coming from the direction of earth core presents an irreducible background. We consider 50kt × 10 years of ICAL running and WIMP masses between 10-100 GeV and present 90% C.L. exclusion sensitivity limits on σ$_{SI}$ which is the WIMP-nucleon Spin Independent (SI) interaction cross-section. The expected sensitivity limits calculated for ICAL for the WIMP annihilation in the earth are more stringent than the limits obtained by any other neutrino detector. For a WIMP mass of 52.14 GeV, where the signal fluxes are enhanced due to resonance capture of WIMP in earth due to Fe nuclei, the sensitivity limits, assuming 100% branching ratio for each channel, are: σ$_{SI}$ = 3.43 × 10$^{−45}$ cm$^{2}$ for ν$_{μ}$ $ {\overline{\nu}}_{\mu } $ channel, σ$_{SI}$ = 1.02 × 10$^{−44}$ cm$^{2}$ for τ$^{+}$τ$^{−}$ channel and σ$_{SI}$ = 5.36 × 10$^{−44}$ cm$^{2}$ for $ b\,\overline{b} $ channel.

  • Collider bounds on 2-Higgs doublet models with U (1)$_X$ gauge symmetries
    Phys.Lett. B793 (2019) 150-160

    by: Camargo, Daniel A. (IIP, Brazil) et al.

    2-Higgs Doublet Models (2HDMs) typically need to invoke an ad-hoc discrete symmetry to avoid severe flavor bounds and in addition feature massless neutrinos, thus falling short of naturally complying with existing data. However, when augmented by an Abelian gauge symmetry naturally incorporating neutrino masses via a type-I seesaw mechanism while at the same time escaping flavor changing interactions, such enlarged 2HDMs become very attractive phenomenologically. In such frameworks, the distinctive element is the $Z'$ gauge boson generated by the spontaneous breaking of the Abelian group $U(1)_X$. In this work, we derive updated collider bounds on it. Several theoretical setups are possible, each with different and sometimes suppressed couplings to quarks and leptons. Thus, complementary data from dijet and dilepton resonance searches need to be considered to fully probe these objects. We employ the corresponding datasets as obtained at the Large Hadron Collider (LHC) at the 13 TeV CMs energy for $\mathcal{L}=12,36$ and $300$ fb$^{-1}$ of luminosity. Moreover, we present the potential sensitivity to such $Z'$s of the High Luminosity LHC (HL-LHC) and High Energy LHC (HE-LHC).

  • Probing heavy neutrino oscillations in rare W boson decays
    0954-3899; 1361-6471
    Journal of Physics G: Nuclear and Particle Physics, Volume 46, Number 7 (2019)

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

    In this work, we study the lepton number violating W boson and top quark decays via intermediate on-shell Majorana neutrinos Nj into three charged leptons and a light neutrino. We discuss the neutrino oscillation effects present in the decay due to the small mass gap between the heavy neutrino states. We focus on a scenario that contains at least two heavy Majorana neutrinos in the mass range 2-80 GeV. The results indicate that the modulation of the branching ratios as a function of the distance between the vertices may be detected in a future experiment such as High-Luminosity Large Hadron Collider. As a secondary result, the CP-violating phases could be explored.

  • New physics vs new paradigms: distinguishing CPT violation from NSI
    Eur.Phys.J. C79 (2019) 390

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

    Our way of describing Nature is based on local relativistic quantum field theories, and then CPT symmetry, a natural consequence of Lorentz invariance, locality and hermiticity of the Hamiltonian, is one of the few if not the only prediction that all of them share. Therefore, testing CPT invariance does not test a particular model but the whole paradigm. Current and future long baseline experiments will assess the status of CPT in the neutrino sector at an unprecedented level and thus its distinction from similar experimental signatures arising from non-standard interactions is imperative. Whether the whole paradigm is at stake or just the standard model of neutrinos crucially depends on that.

  • Muon anomalies and the $SU(5)$ Yukawa relations
    Phys.Rev. D99 (2019) 095003

    by: Cárcamo Hernández, A.E. (Santa Maria U., Valparaiso) et al.

    We show that, within the framework of SU(5) grand unified theories (GUTs), multiple vectorlike families at the GUT scale which transform under a gauged U(1)′ (under which the three chiral families are neutral) can result in a single vectorlike family at low energies which can induce nonuniversal and flavorful Z′ couplings, which can account for the B physics anomalies in RK(*). In such theories, we show that the same muon couplings which explain RK(*) also correct the Yukawa relation Ye=YdT in the muon sector without the need for higher Higgs representations. To illustrate the mechanism, we construct a concrete model based on SU(5)×A4×Z3×Z7 with two vectorlike families at the GUT scale, and two right-handed neutrinos, leading to a successful fit to quark and lepton (including neutrino) masses, mixing angles, and CP phases, where the constraints from lepton-flavor violation require Ye to be diagonal.

  • Fermion Masses and Mixings, Leptogenesis and Baryon Number Violation in Pati-Salam Model
    Nucl.Phys. B943 (2019) 114630

    by: Saad, Shaikh (Oklahoma State U.)

    In this work we study a predictive model based on a partially unified theory possessing the gauge symmetry of the Pati-Salam group, $SU(2)_L\times SU(2)_R\times SU(4)_C$ supplemented by a global Peccei-Quinn symmetry, $U(1)_{PQ}$. A comprehensive analysis of the Higgs potential is carried out in a minimal set-up. The assumed Peccei-Quinn symmetry along with solving the strong CP problem, can provide axion as the dark matter candidate. This minimal set-up with limited number of Yukawa parameters can successfully incorporate the hierarchies in the charged fermion masses and mixings. The automatic existence of the heavy Majorana neutrinos generate the extremely small light neutrino masses through the seesaw mechanism, which is also responsible for producing the observed cosmological matter-antimatter asymmetry of the universe. We find interesting correlation between the low scale neutrino observables and the baryon asymmetry in this model. Baryon number violating nucleon decay processes mediated by the scalar diquarks and leptoquarks in this framework are found to be, $n,p\to \ell+m, \ell^c + m$ ($m=$ meson, $\ell=$ lepton, $\ell^c=$ antilepton) and $n,p\to \ell+\ell^c + \ell^c$. For some choice of the parameters of the theory, these decay rates can be within the observable range. Another baryon number violating process, the neutron-antineutron oscillation can also be in the observable range.

  • Lepton mass and mixing in a simple extension of the Standard Model based on T7 flavor symmetry
    Phys.Atom.Nucl. 82 (2019) 168-182

    by: Vien, V.V. (Tay Nguyen U.) et al.

    A simple Standard Model Extension based on $T_7$ flavor symmetry which accommodates lepton mass and mixing with non-zero $\theta_{13}$ and CP violation phase is proposed. At the tree- level, the realistic lepton mass and mixing pattern is derived through the spontaneous symmetry breaking by just one vacuum expectation value ($v$) which is the same as in the Standard Model. Neutrinos get small masses from one $SU(2)_L$ doublet and two $SU(2)_L$ singlets in which one being in $\underline{1}$ and the two others in $\underline{3}$ and $\underline{3}^*$ under $T_7$ , respectively. The model also gives a remarkable prediction of Dirac CP violation $\delta_{CP}=172.598^\circ$ in both normal and inverted hierarchies which is still missing in the neutrino mixing matrix.

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