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  • CP Violation in Same-sign Dilepton Production at the LHC

    by: Najafi, Fatemeh
    If the neutrino is a Majorana particle, low-energy lepton-number-violating (LNV) processes, such as neutrinoless double-beta ($0\nu\beta\beta$) decay, are possible. It may also be possible to observe high-energy $0\nu\beta\beta$-like LNV processes at the LHC. These are distinguished by the presence of same-sign dileptons in the final state (e.g., ${\bar u} d \to t {\bar b} \, e^- \mu^-$). If such a process were observed, we would then want to know the nature of the underlying new physics (NP). In this paper, we show that CP-violating triple products (TPs) may be present in the process, and much information can be obtained by measuring them. If a nonzero TP were observed, we would know immediately that there are (at least) two interfering NP amplitudes, with different weak phases and different Lorentz structures. And if we had some knowledge of the NP, e.g., by direct production of NP particles, we could get information about the magnitudes and relative phases of its couplings by examining the angular distribution of the final-state particles. If the NP involves right-handed (RH) neutrinos, it may even be possible to probe the CP-violating Dirac and Majorana phases in the RH neutrino mixing matrix.

  • Neutrino and $Z'$ phenomenology in an anomaly-free $\mathbf{U}(1)$ extension: role of higher-dimensional operators

    by: Choudhury, Debajyoti
    We consider an anomaly-free $\mathrm{U}(1)$ extension of the Standard Model with three right-handed neutrinos (RHNs) and two complex scalars, wherein the charge assignments preclude all tree-level mass terms for the neutrinos. Considering this setup, in turn, to be only a low-energy effective theory, we introduce higher-dimensional terms {\em a la} Froggatt-Nielsen to naturally generate tiny neutrino masses. One of the RHNs turns out to be very light, thereby constituting the main decay mode for the $Z'$ and hence relaxing the LHC dilepton resonance search constraints. This very RHN has a lifetime comparable to or bigger than the age of the Universe, and, hence, could account for a non-negligible fraction of the dark matter.

  • Flavor masses and mixing in modular A4 Symmetry

    by: Abbas, Mohamed
    A flavor model based on a $A_4$ modular group is proposed to account for both lepton and quark parameters (masses and mixing). We consider the inverse seesaw mechanism to produce the light neutrino masses. Both neutrino and charged lepton masses are obtained in terms of Yukawa coupling ratios and the module $\tau$ of the $A_4$ modular form. The calculated lepton and quark parameters are in good agreement with the recent data.

  • Five Texture Zeros for Dirac Neutrino Mass Matrices

    by: Benavides, Richard H.
    In this work we propose new five textures zeros for the mass matrices in the lepton sector in order to predict values for the neutrino masses. In our approach we go beyond the Standard Model by assuming Dirac masses for the neutrinos, feature which allows us to make a theoretical prediction for the lightest neutrino mass in the normal ordering. The textures analyzed have enough free parameters to adjust the $V_{\text{\tiny PMNS}}$ mixing matrix including the CP-violating phase, the neutrino mass squared differences $\delta m_{21}^2,\,\delta m_{31}^2$, and the three charged lepton masses. In order to have reliable results two different approaches are used: the first one is based on a least-squares analysis to fit the lepton masses and the mixing parameters to their corresponding experimental values, for this case the best fit for the lightest neutrino mass is $(3.9\pm^{0.6}_{0.8})\times 10^{-3}$ eV.; the second approach is just algebraic, based on the weak basis transformation method, in this case the lightest neutrino mass consistent with the experimental values and the restrictions coming from the five texture zeros of the mass matrices is equal to $(3.5\pm0.9)\times 10^{-3}$ eV.

  • Neutrino Oscillations at low energy long baseline experiments in the presence of nonstandard interactions and parameter degeneracy

    by: Yasuda, Osamu
    We discuss the analytical expression of the oscillation probabilities at low energy long baseline experiments, such as T2HK and T2HKK in the presence of nonstandard interactions (NSIs). We show that these experiments are advantageous to explore the NSI parameters ($\epsilon_D$, $\epsilon_N$), which were suggested to be nonvanishing to account for the discrepancy between the solar neutrino and KamLAND data. We also show that, when the NSI parameters are small, parameter degeneracy in the CP phase $\delta$, $\epsilon_D$ and $\epsilon_N$ can be resolved by combining data of the T2HK and T2HKK experiments.

  • Probing new neutral gauge bosons with CEvNS and neutrino-electron scattering

    by: Miranda, Omar G.
    The potential for probing extra neutral gauge boson mediators ($Z^\prime$) from low-energy measurements is comprehensively explored. Our study mainly focuses on $Z^\prime$ mediators present in string-inspired $E_6$ models and Left-Right symmetry. We estimate the sensitivities of coherent-elastic neutrino-nucleus scattering (CE$\nu$NS) and neutrino-electron scattering experiments. Our results indicate that such low-energy high-intensity measurements can provide a valuable probe, complementary to high-energy collider searches and electroweak precision measurements.

  • Signature of neutrino mass hierarchy in gravitational lensing

    by: Swami, Himanshu
    In flat spacetime, the vacuum neutrino flavour oscillations are known to be sensitive only to the difference between the squared masses, and not to the individual masses, of neutrinos. In this work, we show that the lensing of neutrinos induced by a gravitational source substantially modifies this standard picture and it gives rise to a novel contribution through which the oscillation probabilities also depend on the individual neutrino masses. A gravitating mass located between a source and a detector deflects the neutrinos in their journey, and at a detection point, neutrinos arriving through different paths can lead to the phenomenon of interference. The flavour transition probabilities computed in the presence of such interference depend on the individual masses of neutrinos whenever there is a non-zero path difference between the interfering neutrinos. We demonstrate this explicitly by considering an example of weak lensing induced by a Schwarzschild mass. Through the simplest two flavour case, we show that the oscillation probability in the presence of lensing is sensitive to the sign of $\Delta m^2 = m_2^2 -m_1^2$, for non-maximal mixing between two neutrinos, unlike in the case of standard vacuum oscillation in flat spacetime. Further, the probability itself oscillates with respect to the path difference and the frequency of such oscillations depends on the absolute mass scale $m_1$ or $m_2$. We also give results for realistic three flavour case and discuss various implications of gravitationally modified neutrino oscillations and means of observing them.

  • Oscillating Neutrinos and Majorana Neutrino Masses

    by: Fritzsch, Harald
    The texture zero mass matrices for the leptons and the seesaw mechanism are used to derive relations between the matrix elements of the lepton mixing matrix and the ratios of the neutrino masses.

  • Chiral Abelian gauge theories with few fermions

    by: Costa, Davi B. (Sao Paulo U.) et al.

    We construct chiral theories with the smallest number $n_\chi$ of Weyl fermions that form an anomaly-free set under various Abelian gauge groups. For the $U(1)$ group, where $n_\chi = 5$, we show that the general solution to the anomaly equations is a set of charges given by cubic polynomials in three integer parameters. For the $U(1) \times U(1)$ gauge group we find $n_\chi = 6$, and derive the general solution to the anomaly equations, in terms of 6 parameters. For $U(1) \times U(1) \times U(1)$ we show that $n_\chi = 8$, and present some families of solutions. These chiral gauge theories have potential applications to dark matter models, right-handed neutrino interactions, and other extensions of the Standard Model. As an example, we present a simple dark sector with a natural mass hierarchy between three dark matter components.

  • Self Destructing Atomic DM

    by: Geller, Michael (Tel Aviv U.) et al.

    Self-Destructing Dark Matter (SDDM) is a class of dark sector models in which the collision of a dark sector particle with the earth induces its prompt decay into Standard Model particles, generating unique signals at neutrino detectors. The inherent fragility of SDDM makes its survival from the early universe unlikely, implying a late time production mechanism. We present an efficient late time production mechanism for SDDM based on atomic rearrangement, the mechanism responsible for muon or anti-proton capture in hydrogen. In this model, an atomic rearrangement process occurs in our galaxy, converting dark atoms into highly excited bound states - our SDDM candidates. While the resulting SDDM is only a small fraction of the dark matter flux, its striking self-destruction signals imply a significant discovery reach in the existing data from the Super-Kamiokande experiment.

  • A little theory of everything, with heavy neutral leptons

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

    Recently a new model of "Affleck-Dine inflation" was presented, that produces the baryon asymmetry from a complex inflaton carrying baryon number, while being consistent with constraints from the cosmic microwave background. We adapt this model such that the inflaton carries lepton number, and communicates the lepton asymmetry to the standard model baryons via quasi-Dirac heavy neutral leptons (HNLs) and sphalerons. One of these HNLs, with mass $\lesssim 4.5\,$GeV, can be (partially) asymmetric dark matter (DM), whose asymmetry is determined by that of the baryons. Its stability is directly related to the vanishing of the lightest neutrino mass. Neutrino masses are generated by integrating out heavy sterile neutrinos whose mass is above the inflation scale. The model provides an economical origin for all of the major ingredients missing from the standard model: inflation, baryogenesis, neutrino masses, and dark matter. The HNLs can be probed in fixed-target experiments like SHiP, possibly manifesting $N$-$\bar N$ oscillations. A light singlet scalar, needed for depleting the DM symmetric component, can be discovered in beam dump experiments and searches for rare decays, possibly explaining anomalous events recently observed by the KOTO collaboration. The DM HNL is strongly constrained by direct searches, and could have a cosmologically interesting self-interaction cross section.

  • Bridging the pseudo-Dirac dark matter and radiative neutrino mass in a singlet doublet scenario

    by: Konar, Partha (Ahmedabad, Phys. Res. Lab) et al.

    We examine simple extension of the standard model with a pair of fermions, one singlet and a doublet, in a common thread linking the dark matter problem with the smallness of neutrino masses associated with several exciting features. In the presence of a small bare Majorana mass term, the singlet fermion brings in a pseudo-Dirac dark matter capable of evading the strong spin-independent direct detection bound by suppressing the dark matter annihilation processes mediated by the neutral current. In consequence, the allowed range of mixing angle between the doublet and the singlet fermions gets enhanced substantially. Presence of the same mass term in association of singlet scalars also elevates tiny but nonzero masses radiatively for light Majorana neutrino satisfying observed oscillation data.

  • $\mu$-$\tau$ symmetry breaking and CP violation in the neutrino mass matrix

    by: Fukuyama, Takeshi (Osaka U., Res. Ctr. Nucl. Phys.) et al.

    The $\mu$-$\tau$ exchange symmetry in the neutrino mass matrix and its breaking as a perturbation are discussed. The exact $\mu$-$\tau$ symmetry restricts the 2-3 and 1-3 neutrino mixing angles as $\theta_{23} = \pi/4$ and $\theta_{13} = 0$ at a zeroth order level. We claim that the $\mu$-$\tau$ symmetry breaking prefers a large CP violation to realize the observed value of $\theta_{13}$ and to keep $\theta_{23}$ nearly maximal, though an artificial choice of the $\mu$-$\tau$ breaking can tune $\theta_{23}$, irrespective of the CP phase. We exhibit several relations among the deviation of $\theta_{23}$ from $\pi/4$, $\theta_{13}$ and Dirac CP phase $\delta$, which are useful to test the $\mu$-$\tau$ breaking models in the near future experiments. We also propose a concrete model to break the $\mu$-$\tau$ exchange symmetry spontaneously and its breaking is mediated by the gauge interactions radiatively in the framework of the extended gauge model with $B-L$ and $L_\mu - L_\tau$ symmetries. As a result of the gauge mediated $\mu$-$\tau$ breaking in the neutrino mass matrix, the artificial choice is unlikely, and a large Dirac CP phase is preferable.

  • All-inclusive interacting dark sector cosmologies

    by: Yang, W. (Liaoning Normal U.) et al.

    In this paper we explore possible extensions of Interacting Dark Energy cosmologies, where Dark Energy and Dark Matter interact non-gravitationally with one another. In particular, we focus on the neutrino sector, analyzing the effect of both neutrino masses and the effective number of neutrino species. We consider the Planck 2018 legacy release data combined with several other cosmological probes, finding no evidence for new physics in the dark radiation sector. The current neutrino constraints from cosmology should be therefore regarded as robust, as they are not strongly dependent on the dark sector physics, once all the available observations are combined. Namely, we find a total neutrino mass $M_\nu<0.15$ eV and a number of effective relativistic degrees of freedom of $N_{\rm eff}=3.03^{+0.33}_{-0.33}$, both at 95\% CL, which are close to those obtained within the $\Lambda$CDM cosmology, $M_\nu<0.12$ eV and $N_{\rm eff}=3.00^{+0.36}_{-0.35}$ for the same data combination.

  • Simulation of an experiment on looking for sterile neutrinos at nuclear reactor

    by: Silaeva, S.V. (Moscow, INR) et al.

    The simulation of an experiment on looking for sterile neutrinos at a nuclear reactor at short distances is presented. It has been shown that statistical fluctuations in experimental bins always imitate the oscillatory behavior of the spectrum. An amplitude of the detectable oscillations decreases when statistics growing up in case of oscillations absence, while mass parameter tends to be accidental. When simulating spectra in detectors with oscillations amplitude parameter fluctuates close to simulated value as well as mass parameter.

  • Semileptonic Decays of Charmed Mesons to Light Scalar Mesons

    by: Soni, Nakul R. (Baroda U.) et al.

    Within the framework of Covariant Confined Quark Model, we compute the transition form factors of $D$ and $D_s$ mesons decaying to light scalar mesons $f_0(980)$ and $a_0(980)$. The transition form factors are then utilised to compute the semileptonic branching fractions. We study the channels namely $D_{(s)}^+ \to f_0(980) \ell^+ \nu_\ell$ and $D \to a_0(980) \ell^+ \nu_\ell$ for $\ell = e$ and $\mu$. For computation of semileptonic branching fractions, we consider the $a_0(980)$ meson to be the conventional quark antiquark structure and the $f_0(980)$ meson as the admixture of $s\bar{s}$ and light quark-antiquark pairs. Our findings are found to support the recent BESIII data.

  • The gallium anomaly reassessed using a Bayesian approach

    by: Kostensalo, Joel (Jyvaskyla U.) et al.

    The solar-neutrino detectors GALLEX and SAGE were calibrated by electron-neutrino flux from the $^{37}$Ar and $^{51}$Cr calibration sources. A deficit in the measured neutrino flux was recorded by counting the number of neutrino-induced conversions of the $^{71}$Ga nuclei to $^{71}$Ge nuclei. This deficit was coined ``gallium anomaly'' and it has lead to speculations about beyond-the-standard-model physics in the form of eV-mass sterile neutrinos. Notably, this anomaly has already defied final solution for more than 20 years. Here we reassess the statistical significance of this anomaly and improve the related statistical approaches by treating the neutrino experiments as repeated Bernoulli trials taking into account the fact that the number of the detected $^{71}$Ge nuclei is quite small, thus calling for a Bayesian statistical approach. In addition, we take into account the systematic errors of the experiments, their correlations, theoretical uncertainties and the number of background solar-neutrino events as a Poisson-distributed random variable. To compare with the previously reported statistical significances of the anomaly we convert the posterior intervals of our Bayesian approach to standard deviations $\sigma$ of the frequentist approach. We find that our approach reduces the statistical significance of the anomaly by $0.8\,\sigma$ for all the adopted theoretical approaches. This renders the gallium anomaly a statistically weakly supported concept. Furthermore, the implications of our approach go far beyond the gallium anomaly since the results of many rare-events experiments should be reassessed for their limited number of recorded events.

  • Non-relativistic neutrinos and the weak equivalence principle violation

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

    We study the non-relativistic limit of Dirac equation for mixed neutrinos. We demonstrate that such a procedure inevitably leads to a redefinition of the inertial mass. This happens because, in contrast to the case when mixing is absent, the antiparticle sector contribution cannot be neglected for neutrinos with definite flavor. We then show that, when a gravitational interaction is switched on, in the weak-field approximation the mass parameter which couples to gravity (gravitational mass) does not undergo the same reformulation as the inertial mass, thus leading to a breakdown of the weak equivalence principle.

  • A comparative study of $0\nu\beta\beta$ decay in symmetric and asymmetric left-right model

    by: Majumdar, Chayan (Indian Inst. Tech., Mumbai) et al.

    We study the new physics contributions to neutrinoless double beta decay ($0\nu\beta\beta$) in a TeV scale left-right model with spontaneous D-parity breaking mechanism where the values of the $SU(2)_L$ and $SU(2)_R$ gauge couplings, $g_L$ and $g_R$ are unequal. Neutrino mass is generated in the model via gauge extended inverse seesaw mechanism. We embed the model in a non-supersymmetric $SO(10)$ GUT with a purpose of quantifying the results due to the condition $g_{L} \neq g_{R}$. We compare the predicted numerical values of half life of $0\nu\beta\beta$ decay, effective Majorana mass parameter and other lepton number violating parameters for three different cases; (i) for manifest left-right symmetric model ($g_L = g_R$), (ii) for left-right model with spontaneous D parity breaking ($g_L \neq g_R$), (iii) for Pati-Salam symmetry with D parity breaking ($g_L \neq g_R$). We show how different contributions to $0\nu\beta\beta$ decay are suppressed or enhanced depending upon the values of the ratio $\frac{g_R}{g_L}$ that are predicted from successful gauge coupling unification.

  • Quantum decoherence and relaxation in neutrinos using long-baseline data

    by: Gomes, A.L.G. (Goias U.) et al.

    We investigate the effect of quantum decoherence and relaxation in neutrino oscillations using MINOS and T2K data. The formalism of open quantum systems is used to describe the interaction of a neutrino system with the environment, where the strength of the interaction is regulated by a decoherence parameter $\Gamma$. We assume an energy dependence parameterized by $\Gamma = \gamma_0 (E/\mbox{GeV})^n$, with $n=-2,0,+2$, and study three different scenarios. The MINOS and T2K data present a complementary behavior, with regard to our theoretical model, resulting in a better sensitivity for $n = +2$ and $n = -2$, respectively. We perform a combined analysis of both experimental data and include a reactor constraint on $\sin^2 \theta_{13}$. The results of our combined analyses improve significantly the previous bounds on $\gamma_0$ for $n = -2$, reporting an upper bound of $1.7 \times 10^{-23}$~GeV, at the 90\% confidence level.

  • One-loop matching in the SMEFT extended with a sterile neutrino

    by: Chala, Mikael (CAFPE, Granada) et al.

    We study the phenomenology of the simplest renormalisable model that, at low energy, leads to the effective field theory of the Standard Model extended with right-handed neutrinos ($\nu$SMEFT). Our aim is twofold. First, to contextualise new collider signatures in models with sterile neutrinos so far studied only using the bottom-up approach. And second and more important, to provide a thorough example of one-loop matching in the diagrammatic approach, of which other matching techniques and automatic tools can benefit for cross-checks. As byproducts of this work, we provide for the first time: (i) a complete off-shell basis for the $\nu$SMEFT and explicit relations between operators linked by equations of motion; (ii) a complete basis for the low-energy effective field theory ($\nu$LEFT) and the tree-level matching onto the $\nu$SMEFT; (iii) partial one-loop anomalous dimensions in the $\nu$LEFT. This way, our work comprises a new step forward towards the systematisation of one-loop computations in effective field theories, especially if the SM neutrinos are Dirac.

  • Oscillation tomography of the Earth with solar neutrinos and future experiments

    by: Bakhti, Pouya (IPM, Tehran) et al.

    We study in details the Earth matter effects on the boron neutrinos from the Sun using recently developed 3D models of the Earth. The models have a number of new features of the density profiles, in particular, substantial deviation from spherical symmetry. In this connection we further elaborate on relevant aspects of oscillations ($\epsilon^2$ corrections, adiabaticity violation, entanglement, {\it etc.}) and the attenuation effect. The night excesses of the $\nu e-$ and $\nu N-$ events and the Day-Night asymmetries, $A_{ND}$, are presented in terms of the matter potential and the generalized energy resolution functions. The energy dependences of the cross-section and the flux improve the resolution, and consequently, sensitivity to remote structures of the profiles. The nadir angle ($\eta$) dependences of $A_{ND}$ are computed for future detectors DUNE, THEIA, Hyper-Kamiokande and MICA at the South pole. Perspectives of the oscillation tomography of the Earth with the boron neutrinos are discussed. Next generation of detectors will establish the integrated day-hight asymmetry with high confidence level. They can give some indications of the $\eta-$ dependence of the effect, but will discriminate among different models at most at the $(1 - 2)\sigma$ level. For the high level discrimination, the MICA-scale experiments are needed. MICA can detect the ice-soil borders and perform unique tomography of Antarctica.

  • $\nu \bar{\nu}$-Pair Emission in Neutron-Star Matter based on a Relativistic Quantum Approach

    by: Maruyama, Tomoyuki (Nihon U., Fujisawa) et al.

    We study the neutrino anti-neutrino pair emission from electrons and protons in a relativistic quantum approach. This process occurs only under a strong magnetic field, and it is considered to be one of effective processes for neutron star cooling. In this work we calculate the luminosity of the neutrino anti-neutrino pairs emitted from neutron-star-matter with a magnetic field of about 10^{15} G. We find that the energy loss is much larger than that of the modified Urca process. The neutrino anti-neutrino pair emission processes in strong magnetic fields is expected to contribute significantly to the cooling of the magnetars.

  • Matter vs. vacuum oscillations at long baseline accelerator neutrino experiments

    by: Bharti, Suman (Indian Inst. Tech., Mumbai) et al.

    The neutrino oscillation probabilities at the long baseline accelerator neutrino experiments are expected to be modified by matter effects. We search for evidence of such modification in the data of T2K and NO$\nu$A, by fitting the data to the hypothesis of (a) matter modified oscillations and (b) vacuum oscillations. We find that vacuum oscillations provide as good a fit to the data as matter modified oscillations. Even an extended run of these experiments, with 5 years in neutrino mode and 5 years in anti-neutrino mode, can {\bf not} make a $3~\sigma$ distinction between vacuum and matter modified oscillations. The proposed experiment DUNE, with 5 years in neutrino mode and 5 years in anti-neutrino mode, can rule out vacuum oscillations by itself at $5~\sigma$ if the hierarchy is normal. For inverted hierarchy, a $5~\sigma$ discrimination against vacuum oscillations requires the addition of T2K and NO$\nu$A data to DUNE data.

  • Testing MSW effect in Supernova Explosion with Neutrino event rates

    by: Lai, Kwang-Chang (Chang Gung U.) et al.

    Flavor transitions in supernova neutrinos are yet to be determined. We present a method to probe whether or not the Mikheyev-Smirnov-Wolfenstein effects occur as SN neutrinos propagate outward from the SN core by investigating time evolutions of neutrino event rates for different flavors in different kinds of detectors. As the MSW effect occurs, the $\nu_e$ flux swaps with the $\nu_x$ flux, which represents any one of $\nu_{\mu}$, $\nu_{\tau}$, $\bar{\nu}_{\mu}$, and $\bar{\nu}_{\tau}$ flux, either fully or partially depending on the neutrino mass hierarchy. During the neutronization burst, the $\nu_e$ emission evolves in a much different shape from the emissions of $\bar{\nu}_e$ and $\nu_x$ while the latter two evolve in a similar pattern. Meanwhile, the luminosity of the the $\nu_e$ emission is much larger than those of the $\bar{\nu}_e$ and $\nu_x$ emissions while the latter two are roughly equal. As a consequence, the time-evolution pattern of the $\nu_e{\rm Ar}$ event rates in the absence of the MSW effect will be much different from that in the occurrence of the MSW effect, in either mass hierarchy. With the simulated SN neutrino emissions, the $\nu_e{\rm Ar}$ and inverse beta decay event rates are evaluated. The ratios of the two cumulative event rates are calculated for different progenitor masses up to $100~{\rm ms}$. We show that the time evolutions of this cumulative ratios can effectively determine whether MSW effects really occur for SN neutrinos or not.

  • Effective field theory approach to lepton number violating decays $K^\pm\rightarrow \pi^\mp l^{\pm}_\alpha l^{\pm}_\beta$: long-distance contribution

    by: Liao, Yi (Nankai U.) et al.

    This is a sequel to our recent work [1] in which we calculated the lepton number violating (LNV) $K^\pm$ decays due to contact dimension-9 (dim-9) quark-lepton effective interactions that are induced at a high energy scale. In this work we investigate the long-distance contribution to the decays arising from the exchange of a neutrino. These decays can probe LNV interactions involving the second generation of fermions that are not reachable in nuclear neutrinoless double-$\beta$ decays. Our study is completely formulated in the framework of effective field theories (EFTs), from the standard model effective field theory (SMEFT) through the low energy effective field theory (LEFT) to chiral perturbation theory. We work to the first nontrivial orders in each effective field theory, collect along the way the matching conditions and renormalization group effects, and express the decay branching ratios in terms of the Wilson coefficients associated with the dim-5 and dim-7 operators in SMEFT. Our result is general in that it does not depend on dynamical details of physics at a high scale that induce the effective interactions in SMEFT and in that it does not appeal to any hadronic models. We find that the long-distance contribution overwhelmingly dominates over the contact or short-distance one. Assuming the new physics scale to be around a TeV, the branching ratios are predicted to be below the current experimental upper bounds by several orders of magnitude.

  • Revealing neutrino nature and $CPT$ violation with decoherence effects

    by: Buoninfante, Luca (Tokyo Inst. Tech.) et al.

    We study decoherence effects on mixing among three generations of neutrinos. We show that in presence of a non--diagonal dissipation matrix, both Dirac and Majorana neutrinos can violate the $CPT$ symmetry and the oscillation formulae depend on the parametrization of the mixing matrix. We reveal the $CP$ violation in the transitions preserving the flavor, for a certain form of the dissipator. In particular, the $CP$ violation affects all the transitions in the case of Majorana neutrinos, unlike Dirac neutrinos which still preserve the $CP$ symmetry in one of the transitions flavor preserving. This theoretical result shows that decoherence effects, if exist for neutrinos, could allow to determine the neutrino nature and to test fundamental symmetries of physics. Next long baseline experiments could allow such an analysis. We relate our study with experiments by using the characteristic parameters and the constraints on the elements of the dissipation matrix of current experiments.

  • Realization of the minimal extended seesaw mechanism and $TM_2$ type neutrino mixing in the light of $A_4\times C_4$ symmetry group

    by: Krishnan, R. (Saha Inst.) et al.

    We study the phenomenology of an $A_4\times C_4$ based neutrino mass model accommodating a light sterile neutrino in the minimal extended seesaw scheme. Mass terms consisting of the Standard Model neutrinos, the right-handed heavy neutrinos and the sterile neutrinos are obtained in terms of the vacuum alignments of a set of flavons transforming under $A_4\times C_4$. The corresponding mass matrices when incorporated into the MES formula, give rise to the $\text{TM}_2$ mixing pattern having non-zero reactor angle. We express all the active and the sterile oscillation observables in terms of only four real model parameters. Using this highly constrained scenario we predict $\sin^2 \theta_{23} =0.545^{+0.003}_{-0.004}$, $\sin \delta = -0.911^{+0.006}_{-0.005}$, $|U_{e4}|^2 = 0.029^{+0.009}_{-0.008}$, $|U_{\mu4}|^2 = 0.010^{+0.003}_{-0.003}$ and $|U_{\tau4}|^2 = 0.006^{+0.002}_{-0.002}$ which are consistent with the current data.

  • Revamped Bi-Large neutrino mixing with Gatto-Sartori-Tonin like relation

    by: Roy, Subhankar (Gauhati U.) et al.

    The Gatto Sartori Tonin (GST) relation which establishes the Cabibbo angle in terms of the quark mass ratio: $\theta_{C}=\sqrt{m_d/m_s}$, is instituted as $\theta_{13}=\sqrt{m_1/m_3}$ to a Bi-large motivated lepton mixing framework that relies on the unification of mixing parameters: $\theta_{13}=\theta_{C}$ and $\theta_{12}=\theta_{23}$. This modification in addition to ruling out the possibility of vanishing $\theta_{13}$, advocates for a nonzero lowest neutrino mass and underlines the normal ordering of the neutrino masses. The framework is further enhanced by the inclusion of a charged lepton diagonalizing matrix $U_{lL}$ with $ (\theta_{12}^l \sim \theta_C, \delta=0)$. The model being architected at the Grand unification theory (GUT) scale is further run down upto the $Z$ boson scale to understand the universality of the GST relation and the Cabibbo angle.

  • When $\tan \beta$ meets all the mixing angles

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

    Models with two-Higgs-doublets and natural flavor conservation contain $\tan \beta = v_2 / v_1$ as a physical parameter. We offer here a generalization of a recently proposed idea where only the Cabibbo angle, $\theta_\text{c} \simeq 0.22$, was related to $\tan \beta$ by virtue of the $\mathbb{D}_{4}$ dihedral symmetry group. The original proposal consisted of a massless first generation of quarks and no mixing with the third generation. In our case, through the addition of a third Higgs doublet with a small vacuum-expectation-value but very large masses, thus later decoupling, all quarks become massive and quark mixing is fully reproduced. In fact, all quark mixing angles are expressed in terms of $\tan \beta$ and one recovers trivial mixing in the limit $\beta \rightarrow 0$. We also explore the consequences in lepton mixing by adopting a type I seesaw mechanism with three heavy right-handed neutrinos.

  • Large Star/Rose Extra Dimension with Small Leaves/Petals

    by: Nortier, Florian (IJCLab, Orsay)

    Scenarii with Large Extra Dimensions (LEDs) compactified on a ($q \leq 7$)D torus and with the Standard Model (SM) fields localized on a 3-brane reformulate the gauge hierarchy problem between the 4D Planck scale $\Lambda_P^{(4)} \sim 10^{18}$ GeV and the electroweak scale $\Lambda_{EW} \sim 100$ GeV as a geometrical hierarchy problem: gravity is strongly coupled at the $(4+q)D$ Planck scale $\Lambda_P^{(4+q)} \sim \mathcal{O}(1)$ TeV, but the compactification radii need to be stabilized at large values compared to the $(4+q)$D Planck length $1/\Lambda_P^{(4+q)}$. In this article, we propose to compactify a single LED on a star/rose graph with a large number of identical leaves/petals of length/circumference of $\mathcal{O}(1/\Lambda_{EW})$, where the 5D Planck scale is $\Lambda_P^{(5)} \sim \mathcal{O}(1)$ TeV (without a large geometrical hierarchy to stabilize). The 4D SM fields are localized at the central vertex of the star/rose graph. We predict a feebly coupled tower of KK-gravitons invisible in current experiments with a KK scale of $\mathcal{O}(\Lambda_{EW})$. Our scenarii lead also to TeV scale strongly coupled gravitational phenomena and to an infinite tower of trans-TeV semi-classical black holes. If there is a stable black hole remnant after evaporation, the Planckion, it could constitute a part of dark matter. Moreover, we propose a toy model to generate light Dirac neutrinos, where the right-handed neutrinos are KK modes of gauge singlet fermions propagating in the extra dimension. In our models, a large number of KK-gravitons and of sterile KK-neutrinos interact only with gravity and constitute a hidden sector.

  • Higgs Inflation, Vacuum Stability, and Leptogenesis

    by: Barrie, Neil D. (Tokyo U., IPMU) et al.

    We consider the introduction of a complex scalar field carrying a global lepton number charge to the Standard Model and the Higgs inflation framework. The conditions are investigated under which this model can simultaneously ensure Higgs vacuum stability up to the Planck scale, successful inflation, non-thermal Leptogenesis via the pendulum mechanism, and light neutrino masses. These can be simultaneously achieved when the scalar lepton is minimally coupled to gravity, that is, when standard Higgs inflation and reheating proceed without the interference of the additional scalar degrees of freedom. If the scalar lepton also has a non-minimal coupling to gravity, a multi-field inflation scenario is induced, with interesting interplay between the successful inflation constraints and those from vacuum stability and Leptogenesis. The parameter region that can simultaneously achieve the above goals is explored.

  • Gravitational waves from neutrino mass and dark matter genesis

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

    We introduce a model in which the genesis of dark matter and neutrino masses is associated with a first order phase transition of a scalar singlet field. During the phase transition a source right-handed neutrino acquires a spacetime-dependent mass dynamically, a small fraction of which is converted via resonant oscillations into a very weakly mixed dark right-handed neutrino with the observed dark matter relic abundance. Neutrino masses are generated via a traditional two right-handed neutrino type-I seesaw between a third right-handed neutrino and the source neutrino. The gravitational waves produced during the phase transition have a peak frequency that increases with the dark matter mass, and are detectable at future gravitational wave interferometers for dark matter masses in the 1 MeV - 20 GeV range. For source right-handed neutrinos heavier than a GeV, successful leptogenesis is also possible.

  • Baryon asymmetry from left-right phase transition
    Phys.Lett. B801 (2020) 135178

    by: Gu, Pei-Hong (Southeast U., Nanjing)

    We extend the standard model fermions by a mirror copy to realize a left-right symmetry. During a strongly first order phase transition of the spontaneous left-right symmetry breaking, the CP-violating reflections of the mirror fermions off the mirror Higgs bubbles can generate a mirror lepton asymmetry and an equal mirror baryon asymmetry. We then can obtain an ordinary baryon asymmetry through the mirror fermion decays where a dark matter scalar plays an essential role. Benefitted from a parity symmetry for solving the strong CP problem, the cosmic baryon asymmetry can be well described by the ordinary lepton mass matrices up to an overall factor. In this scenario, the Dirac CP phase in the Majorana neutrino mass matrix can provide a unique source for the required CP violation. Furthermore, the Higgs triplet for type-II seesaw as well as the first generation of mirror charged fermions can be allowed at the TeV scale.

  • A testable hidden-sector model for Dark Matter and neutrino masses
    JHEP 2002 (2020) 068

    by: Gehrlein, Julia (Brookhaven) et al.

    We consider a minimal extension of the Standard Model with a hidden sector charged under a dark local $U(1)'$ gauge group, accounting simultaneously for light neutrino masses and the observed Dark Matter relic abundance. The model contains two copies of right-handed neutrinos which give rise to light neutrino-masses via an extended seesaw mechanism. The presence of a stable Dark-Matter candidate and a massless state naturally arise by requiring the simplest anomaly-free particle content without introducing any extra symmetries. We investigate the phenomenology of the hidden sector considering the $U(1)'$ breaking scale of the order of the electroweak scale. Confronting the thermal history of this hidden-sector model with existing and future constraints from collider, direct and indirect detection experiments provides various possibilities of probing the model in complementary ways as every particle of the dark sector plays a specific cosmological role. Across the identified viable parameter space, a large region predicts a sizable contribution to the effective relativistic degrees-of-freedom in the early Universe that allows to alleviate the recently reported tension between late and early measurements of the Hubble constant.

  • Weak Structure Functions in $\nu_l-N$ and $\nu_l-A$ Scattering with Nonperturbative and Higher Order Perturbative QCD Effects
    Phys.Rev. D101 (2020) 033001

    by: Zaidi, F. (Aligarh Muslim U.) et al.

    We study the effect of various perturbative and nonperturbative QCD corrections on the free nucleon structure functions ($F_{iN}^{WI}(x,Q^2); ~i=1-3$) and their implications in the determination of nuclear structure functions. The evaluation of the nucleon structure functions has been performed by using the MMHT 2014 PDFs parameterization, and the TMC and HT effects are incorporated following the works of Schienbein et al. and Dasgupta et al., respectively. These nucleon structure functions are taken as input in the determination of nuclear structure functions. The numerical calculations for the $\nu_l/\bar\nu_l-A$ DIS process have been performed by incorporating the nuclear medium effects like Fermi motion, binding energy, nucleon correlations, mesonic contributions, shadowing and antishadowing in several nuclear targets such as carbon, polystyrene scintillator, iron and lead which are being used in MINERvA, and in argon nucleus which is relevant for the ArgoNeuT and DUNE experiments. The differential scattering cross sections $\frac{d^2\sigma_A^{WI}}{dx dy}$ and $(\frac{d\sigma_A^{WI}}{dx}/\frac{d\sigma_{CH}^{WI}}{dx})$ have also been studied in the kinematic region of MINERvA experiment. The theoretical results are compared with the recent experimental data of MINERvA and the earlier data of NuTeV, CCFR, CDHSW and CHORUS collaborations. Moreover, a comparative analysis of the present results for the ratio $(\frac{d\sigma_A^{WI}}{dx}/\frac{d\sigma_{CH}^{WI}}{dx})$, and the results from the MC generator GENIE and other phenomenological models of Bodek and Yang, and Cloet et al., has been performed in the context of MINERvA experiment. The predictions have also been made for $\bar\nu_l-A$ cross section relevant for MINERvA experiment.

  • Interplay between nonstandard and nuclear constraints in coherent elastic neutrino-nucleus scattering experiments
    Phys.Rev. D101 (2020) 035012

    by: Canas, B.C. (Pamplona U.) et al.

    New measurements of the coherent elastic neutrino-nucleus scattering (CEvNS) are expected to be achieved in the near future by using two neutrino production channels with different energy distributions: the very low energy electron antineutrinos from reactor sources and the muon and electron neutrinos from spallation neutron sources (SNS) with a relatively higher energy. Although precise measurements of this reaction would allow an improved knowledge of standard and beyond the Standard Model physics, it is important to distinguish the different new contributions to the process. We illustrate this idea by constraining the average neutron root mean square (rms) radius of the scattering material, as a standard physics parameter, together with the nonstandard interactions (NSI) contribution as the new physics formalism. We show that the combination of experiments with different neutrino energy ranges could give place to more robust constraints on these parameters as long as the systematic errors are under control.

  • Improved global fit to Non-Standard neutrino Interactions using COHERENT energy and timing data
    JHEP 2002 (2020) 023

    by: Coloma, Pilar (Valencia U., IFIC) et al.

    We perform a global fit to neutrino oscillation and coherent neutrino-nucleus scattering data, using both timing and energy information from the COHERENT experiment. The results are used to set model-independent bounds on four-fermion effective operators inducing non-standard neutral-current neutrino interactions. We quantify the allowed ranges for their Wilson coefficients, as well as the status of the LMA-D solution, for a wide class of new physics models with arbitrary ratios between the strength of the operators involving up and down quarks. Our results are presented for the COHERENT experiment alone, as well as in combination with the global data from oscillation experiments. We also quantify the dependence of our results for COHERENT with respect to the choice of quenching factor, nuclear form factor, and the treatment of the backgrounds.

  • Unified SU(4) theory for the $R_{D^{(*)}}$ and $R_{K^{(*)}}$ anomalies
    Phys.Rev. D101 (2020) 015026

    by: Balaji, Shyam (Sydney U.) et al.

    We propose a chiral Pati-Salam theory based on the gauge group SU(4)C×SU(2)L×SU(2)R. The left-handed quarks and leptons are unified into a fundamental representation of SU(4)C, while right-handed quarks and leptons have a separate treatment. The deviations measured in the rare semileptonic decays B→D(*)τν¯ are explained by a scalar leptoquark which couples to right-handed fields and is contained in the SU(4)C×SU(2)R-breaking scalar multiplet. The measured deviation of lepton flavor universality in the rare decays B¯→K¯(*)ℓ+ℓ-, ℓ=μ, e is explained via the SU(4)C leptoquark gauge boson. The model predicts a new sub-GeV scale sterile neutrino which participates in the anomaly and can be searched for in upcoming neutrino experiments. The theory satisfies the current most sensitive experimental constraints and its allowable parameter regions will be probed as more precise measurements from the LHCb and Belle II experiments become available.

  • Effective-field theory analysis of the $\tau^{-}\to K^{-}(\eta^{(\prime)},K^{0}) \nu_{\tau}$ decays
    Phys.Rev. D101 (2020) 034010

    by: Gonzàlez-Solís, Sergi (Indiana U.) et al.

    We analyze the decays $\tau^-\to K^-(\eta^{(\prime)},K^0) \nu_\tau$ within an effective field theory that includes the most general interactions between Standard Model fields up to dimension six, assuming left-handed neutrinos. In particular, we examine different interesting phenomenological observables i.e. decay spectra and branching ratio, Dalitz plot distributions and the forward-backward asymmetry, to explore the sensitivity of the corresponding decays to the effects of non-standard interactions. A controlled theoretical input on the Standard Model hadronic form factors, based on chiral symmetry, dispersion relations, data and asymptotic QCD properties, has allowed us to set bounds on the New Physics scalar and tensor effective couplings using the measured branching ratios. These are found to be in line with the findings of our series of previous analyses of two-meson tau decays and less precise than the constraints obtained from semileptonic kaon decays. In order to set stringent limits on these couplings, we will use all available experimental data of all possible di-meson tau decays. This is our next step plan, that we hope to be of interest for future experimental analyses of these decays.

  • Two-Higgs-Doublet Models with a Flavored $\mathbb{Z}_2$
    Phys.Rev. D101 (2020) 035013

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

    Two Higgs-doublet models usually consider an ad-hoc $\mathbb{Z}_2$ discrete symmetry to avoid flavor changing neutral currents. We consider a new class of two Higgs-doublet models where $\mathbb{Z}_2$ is enlarged to the symmetry group ${\cal{F}}\rtimes \mathbb{Z}_2$, i.e. an inner semi-direct product of a discrete symmetry group ${\cal{F}}$ and $\mathbb{Z}_2$. In such a scenario the symmetry constrains the Yukawa interactions but goes unnoticed by the scalar sector. In the most minimal scenario, $\mathbb{Z}_3 \rtimes \mathbb{Z}_2 = D_3$, flavor changing neutral currents mediated by scalars are absent at tree and one-loop level, while at the same time predictions to quark and lepton mixing are obtained, namely a trivial CKM matrix and a PMNS matrix (upon introduction of three heavy right-handed neutrinos) containing maximal atmospheric mixing. Small extensions allow to fully reproduce mixing parameters, including cobimaximal mixing in the lepton sector (maximal atmospheric mixing and a maximal $CP$ phase).

  • MeV-GeV $\gamma$-ray telescopes probing axino LSP/gravitino NLSP as dark matter in the $\mu\nu$SSM
    JCAP 2001 (2020) 058

    by: Gómez-Vargas, Germán A. (Chile U., Catolica) et al.

    Axino and gravitino are promising candidates to solve the dark matter (DM) problem in the framework of supersymmetry. In this work, we assume that the axino is the lightest supersymmetric particle (LSP), and therefore contributes to DM . In the case of R-parity violating models, the axino can decay into a neutrino-photon pair with a lifetime much longer than the age of the Universe, yielding a potentially detectable signal. Interestingly, a gravitino next-to-LSP (NLSP) can live enough as to contribute to the relic density. We study both scenarios, only axino LSP as DM, and axino LSP with gravitino NLSP as DM . We carry out the analysis in the context of the μνSSM, which solves the μ problem and reproduces neutrino data, only adding couplings involving right-handed neutrinos. In particular, we perform a complete analysis of the relevant parameter space of the model considering constraints from neutrino physics, cosmological observations, and γ-ray detection. We find that the axino or the gravitino can produce a signal detectable by future MeV-GeV γ-ray telescopes. In addition, in a parameter region where we get a well-tempered mixture of both particles, a double-line signal arises as a smoking gun.

  • A New Theory Framework for the Electroweak Radiative Corrections in $K_{l3}$ Decays
    JHEP 2002 (2020) 069

    by: Seng, Chien-Yeah (Bonn U.) et al.

    We propose a new theory framework to study the electroweak radiative corrections in K$_{l3}$ decays by combining the classic current algebra approach with the modern effective field theory. Under this framework, the most important $ \mathcal{O} $(G$_{F}$α) radiative corrections are described by a single tensor T$^{μν}$ involving the time-ordered product between the charged weak current and the electromagnetic current, and all remaining pieces are calculable order-by-order in Chiral Perturbation Theory. We further point out a special advantage in the $ {K}_{l3}^0 $ channel that it suffers the least impact from the poorly-constrained low-energy constants. This finding may serve as a basis for a more precise extraction of the matrix element V$_{us}$ in the future.

  • Neutrino-electron elastic scattering for flux determination at the DUNE oscillation experiment
    Phys.Rev. D101 (2020) 032002

    by: Marshall, Chris M. (LBL, Berkeley) et al.

    We study the feasibility of using neutrino-electron elastic scattering to measure the neutrino flux in the DUNE neutrino oscillation experiment. The neutrino-electron scattering cross section is precisely known, and the kinematics of the reaction allow the determination of the incoming neutrino energy by precise measurement of the energy and angle of the recoiling electron. For several possible near detectors, we perform an analysis of their ability to measure neutrino flux in the presence of backgrounds and uncertainties. With realistic assumptions about detector masses, we find that a liquid argon detector, even with limitations due to angular resolution, is able to perform better than less dense detectors with more precise event-by-event neutrino energy measurements. We find that the absolute flux normalization uncertainty can be reduced from ∼8% to ∼2%, and the uncertainty on the flux shape can be reduced by ∼20%–30%.

  • A modular $A_4$ symmetry realization of two-zero textures of the Majorana neutrino mass matrix
    Nucl.Phys. B952 (2020) 114935

    by: Zhang, Di (Beijing, Inst. High Energy Phys.)

    We show how to realize two-zero textures of the Majorana neutrino mass matrix $M_\nu$ based on modular $A_4$ invariant models without flavons. In these models, all matter fields are assigned to three inequivalent singlets, ${\bf 1}$, ${\bf 1^\prime}$ and ${\bf 1^{\prime\prime}}$, of the finite modular group $\Gamma_3 \simeq A_4$. Considering tensor products of the $A_4$ group, it is easy to make the charged lepton mass matrix $M_\ell$ diagonal. Since not all modular forms of a specific weight and level 3 can be arranged into three inequivalent singlets of $A_4$ simultaneously, we can always make some entries in $M_\nu$ vanish by properly assigning the representations and modular weights for the matter fields. We consider two cases where neutrino masses originate from the Weinberg operator and the type-I seesaw mechanism, respectively. For the former case, all seven viable two-zero textures of $M_\nu$ (${\bf A_{1,2}}$, ${\bf B_{1,2,3,4}}$ and ${\bf C}$) can be realized successfully. For the latter case, only five of them (namely ${\bf A_{1,2}}$, ${\bf B_{3,4}}$ and ${\bf C}$) can be achieved due to the intrinsic structure of the right-handed neutrino mass matrix $M_{\rm R}$ in our assumption for simplicity.

  • Neutrino oscillations in supernovae: angular moments and fast instabilities
    Phys.Rev. D101 (2020) 043009

    by: Johns, Lucas (UC, San Diego) et al.

    Recent theoretical work indicates that the neutrino radiation in core-collapse supernovae may be susceptible to flavor instabilities that set in far behind the shock, grow extremely rapidly, and have the potential to profoundly affect supernova dynamics and composition. Here we analyze the nonlinear collective oscillations that are prefigured by these instabilities. We demonstrate that a zero-crossing in $n_{\nu_e} - n_{\bar{\nu}_e}$ as a function of propagation angle is not sufficient to generate instability. Our analysis accounts for this fact and allows us to formulate complementary criteria. Using Fornax simulation data, we show that fast collective oscillations qualitatively depend on how forward-peaked the neutrino angular distributions are.

  • A Left-Right Mirror Symmetric Model: Common Origin of Neutrino Mass, Baryon Asymmetry and Dark Matter
    JHEP 2001 (2020) 148

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

    I suggest a left-right mirror symmetric particle model as the natural and aesthetic extension of the SM. As the left-right mirror symmetry breaking, the tiny neutrino mass is generated by the radiative mechanism, the baryon asymmetry through the leptogenesis arises from the characteristic decay of the TeV-scale mirror charged lepton, and a KeV-mass sterile Dirac fermion eventually becomes the CDM. The model can completely account for the common origin of the neutrino mass, the baryon asymmetry and the dark matter, moreover, profoundly uncover the internal connections among them. Finally, I discuss several feasible approaches to test the model predictions and probe the new physics by near future experiments.

  • Covert symmetries in the neutrino mass matrix
    JHEP 2002 (2020) 066

    by: Björkeroth, Fredrik (Frascati) et al.

    The flavour neutrino puzzle is often addressed by considering neutrino mass matrices $m$ with a certain number of vanishing entries ($m_{ij}=0$ for some values of the indices), since a reduction in the number of free parameters increases the predictive power. Symmetries that can enforce textures zero can also enforce a more general type of conditions $f(m_{ij})=0$ with $f$ some function of the matrix elements $m_{ij}$. In this case $m$ can have all entries non-vanishing with no reduction in its predictive power. We classify all generation-dependent $U(1)$ symmetries which, in the presence of two leptonic Higgs doublets, can reduce the number of independent high-energy parameters of type-I seesaw to the minimum number compatible with non-vanishing neutrino mixings and CP violation. These symmetries are broken above the scale where the effective operator is generated and can thus remain covert, in the sense that no explicit evidence of the symmetry can be read off the neutrino mass matrix, and different symmetries can give rise to the same low-energy structure. We find that only two cases are viable: one yields a structure with two zero-textures already considered in the literature, the other has no zero-textures and has never been considered before. It predicts normal ordering, a lightest neutrino mass $ \sim 10$ meV, a Dirac phase $\delta \sim \frac{3\pi}{2}$ and definite values for the Majorana phases.

  • Dirac neutrino mass generation from Majorana messenger
    Phys.Rev. D101 (2020) 035004

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

    The radiative type-I seesaw has been already implemented to explain the lightness of Majorana neutrinos with both Majorana and Dirac heavy fermions, and the lightness of Dirac neutrinos with Dirac heavy fermions. In this work, we present a minimal implementation of the radiative type-I seesaw with light Dirac neutrinos and heavy Majorana fermions. An inert doublet and a complex singlet scalar complete the dark sector, which is protected by an Abelian fermiophobic gauge symmetry that also forbids tree level mass contributions for the full set of light neutrinos. A fermion vectorlike extension of the model is also proposed where the light right-handed neutrinos can thermalize in the primordial plasma and the extra gauge boson can be directly produced at colliders. In particular, the current upper bound on ΔNeff reported by PLANCK points to large ratios of MZ′/g′≳40  TeV, which can be competitive with collider constraint for g′ sufficiently large in the ballpark of the Standard Model values, while future cosmic microwave background experiments may probe all the no minimal models presented here.

  • Charged lepton flavor change and nonstandard neutrino interactions
    Phys.Rev. D101 (2020) 015010

    by: Davidson, Sacha (U. Montpellier 2, LUPM) et al.

    Nonstandard neutrino interactions (NSI) are vector contact interactions involving two neutrinos and two first generation fermions, which can affect neutrino propagation in matter. SU(2) gauge invariance suggests that NSI should be accompanied by more observable charged lepton contact interactions. However, these can be avoided at tree level in various ways. We focus on lepton flavour-changing NSI, suppose they are generated by new physics heavier than mW that does not induce (charged) lepton flavor violation (LFV) at tree level, and show that LFV is generated at one loop in most cases. The current constraints on charged lepton flavor violation therefore suggest that μ↔e flavor-changing NSI are unobservable and τ↔ℓ flavor-changing NSI are an order of magnitude weaker than the weak interactions. This conclusion can be avoided if the heavy new physics conspires to cancel the one-loop LFV, or if NSI are generated by light new physics to which our analysis does not apply.

  • A note on the predictions of models with modular flavor symmetries
    TUM-HEP 1223/19
    Phys.Lett. B801 (2020) 135153

    by: Chen, Mu-Chun (UC, Irvine) et al.

    Models with modular flavor symmetries have been thought to be highly predictive. We point out that these predictions are subject to corrections from non-holomorphic terms in the Lagrangean. Specifically, in the models discussed in the literature, the K\"ahler potential is not fixed by the symmetries, for instance. The most general K\"ahler potential consistent with the symmetries of the model contains additional terms with additional parameters, which reduce the predictive power of these constructions. We also comment on how one may conceivably retain the predictivity.

  • Modular $A_4$ invariance and leptogenesis
    JHEP 2001 (2020) 144

    by: Asaka, Takehiko (Niigata U.) et al.

    We consider a model with three right-handed neutrinos in which Yukawa coupling constants and Majorana masses are obtained by requiring the modular $A_4$ symmetry. It has been shown that the model can explain mass hierarchies and mixing patterns of charged leptons and neutrinos with the seesaw mechanism. In this article we investigate the leptogenesis by decays of right-handed neutrinos in this model. It is shown that masses of right-handed neutrinos are about $10^{13}$ GeV in order to account for the observed baryon asymmetry of the universe. Furthermore, the positive sign of the baryon asymmetry is obtained only for the limited ranges of mixing angles and CP violation phases of active neutrinos, which can be tested by future neutrino experiments.

  • Effective field theory approach to lepton number violating decays $K^\pm\rightarrow \pi^\mp l^{\pm}l^{\pm}$: short-distance contribution
    JHEP 2001 (2020) 127

    by: Liao, Yi (Nankai U.) et al.

    This is the first paper of our systematic efforts on lepton number violating (LNV) hadronic decays in the effective field theory approach. These decays provide information complementary to popular nuclear neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay in that they can probe LNV interactions involving heavier quarks and charged leptons. We may call them hadronic $0\nu\beta\beta$ decays in short, though $\beta$ refers to all charged leptons. In this work we investigate the decays $K^\pm\rightarrow\pi^\mp l^{\pm}l^{\pm}$ that arise from short-distance or contact interactions involving four quark fields and two charged lepton fields, which have canonical dimension nine (dim-9) at leading order in low energy effective field theory (LEFT). We make a complete analysis on the basis of all dim-9 operators that violate lepton number by two units, and compute their one-loop QCD renormalization effects. We match these effective interactions in LEFT to those in chiral perturbation theory ($\chi$PT) for pseudoscalar mesons, and determine the resulting hadronic low energy constants (LECs) by chiral symmetry and lattice results in the literature. The obtained decay rate is general in that all physics at and above the electroweak scale is completely parameterized by the relevant Wilson coefficients in LEFT and hadronic LECs in $\chi$PT. Assuming the standard model effective field theory (SMEFT) is the appropriate effective field theory between some new physics scale and the electroweak scale, we match our LEFT results to SMEFT whose leading effective interactions arise from LNV dim-7 operators. This connection to SMEFT simplifies significantly the interaction structures entering in the kaon decays, and we employ the current experimental bounds to set constraints on the relevant Wilson coefficients in SMEFT.

  • Probe Of Sterile Neutrinos Using Astrophysical Neutrino Flavor
    JCAP 2002 (2020) 015

    by: Argüelles, Carlos A. (MIT, Cambridge, Dept. Phys.) et al.

    In this paper, we study the effect of active-neutrino-sterile-neutrino mixing in the expected high-energy astrophysical neutrino flavor content. Non-unitarity in the measurement of the three active neutrinos can be due to the existence of sterile neutrino states. We introduce the concept of the four-flavor tetrahedron in order to visualize the lack of unitarity in the astrophysical neutrino three-flavor triangle. We demonstrate that active-sterile neutrino mixings modify the allowed region of the astrophysical flavor ratio from the standard case. However, a projection of the four-flavor tetrahedron has restrictions of phase space similar to the three-flavor triangle. On the other hand, the initial presence of astrophysical sterile neutrinos drastically changes the scenario, and it allows an apparent unitarity violation in the three-flavor triangle space. Using current global fit constraints including the non-unitarity case, we also illustrate the allowed astrophysical neutrino flavor ratios. Thus, the measurement of the high-energy astrophyscal neutrino flavor content allows us to explore sterile neutrinos independently of the sterile neutrino mass scale. These are topics of investigation for current and future neutrino telescopes.

  • Searching for Heavy Neutrinos with the MoEDAL-MAPP Detector at the LHC
    Phys.Lett. B802 (2020) 135204

    by: Frank, Mariana (Concordia U., Montreal, Dept. Phys.) et al.

    We present a strategy for searching for heavy neutrinos at the Large Hadron Collider using the MoEDAL Experiment's MAPP detector. We hypothesize the heavy neutrino to be a member of a fourth generation lepton doublet, with the electric dipole moment (EDM) introduced within a dimension-five operator. In this model the heavy neutrino is produced in association with a heavy lepton. According to our current experimental and theoretical understanding, the electric dipole moment of this heavy neutrino may be as high as $10^{-15}$ $e$ cm. Taking advantage of the sensitivity of MoEDAL detector, we examine the possibility of detecting such a heavy neutrino in the MAPP as an apparently fractionally charged particle, via ionization due to the neutrino's EDM.

  • Lepton number violation in heavy Higgs boson decays to sneutrinos
    Phys.Rev. D101 (2020) 015018

    by: Moretti, Stefano (Rutherford) et al.

    We study the possibility of observing lepton number violation in the right-handed sneutrino sector of the next-to-minimal supersymmetric Standard Model extended with right-handed neutrinos. The scalar potential introduces a lepton number violating mass term for the right-handed sneutrinos, which generates a phase difference that results in oscillations between the sneutrino and antisneutrino. If we have light Higgsinos and right-handed sneutrinos, the sneutrino decay width is determined by the tiny Yukawa couplings, which allows the phase difference to accumulate before the sneutrino decays. We investigate the possibilities of producing sneutrino pairs resonantly through a heavy Higgs of such a model and the ability of seeing a lepton number violating signature emerging from sneutrinos at the Large Hadron Collider. We also discuss how a possible future signal of this type could be used to determine the neutrino Yukawa couplings.

  • Testing Texture Two Zero Neutrino Mass Matrices Under Current Experimental Scenario
    EPL 129 (2020) 11002

    by: Singh, Madan
    The latest data from Planck collaboration has presented an improved sensitivity limit of the sum of neutrino masses ($\Sigma$), $\Sigma <0.17eV$ at 95$\%$ confidence level (CL). On the other hand, the updated global fits of neutrino oscillation have shown a refined range of atmospheric mixing angle $\theta_{23}$ at the same CL. In the light of these observations, we have re-investigated the five viable cases ( $B_{1, 2, 3, 4}$ and $C$) of texture two zero Majorana mass matrix in the flavor basis. Using the present Planck's data, we have demonstrated that only cases $B_{2}$ and $B_{4}$ are now viable for normal mass ordering, while remaining three cases does not meet the present experimental constraints at 2$\sigma$ CL. The viable cases are also found to be in agreement with the latest T2K, Super-Kamiokande and NO$\nu$A results, indicating the preference for normal neutrino mass ordering ($m_{1} < m_{2} 45^{0}$). In addition, the implication of $\Sigma$ on neutrinoless double beta decay is studied for viable cases.

  • Modular Invariant Models of Lepton Masses at Levels 4 and 5
    JHEP 2002 (2020) 001

    by: Criado, Juan Carlos (Granada U., Theor. Phys. Astrophys.) et al.

    We explore alternative descriptions of the charged lepton sector in modular invariant models of lepton masses and mixing angles. In addition to the modulus, the symmetry breaking sector of our models includes ordinary flavons. Neutrino mass terms depend only on the modulus and are tailored to minimize the number of free parameters. The charged lepton Yukawa couplings rely upon the flavons alone. We build modular invariant models at levels 4 and 5, where neutrino masses are described both in terms of the Weinberg operator or through a type I seesaw mechanism. At level 4, our models reproduce the hierarchy among electron, muon and tau masses by letting the weights play the role of Froggatt-Nielsen charges. At level 5, our setup allows the treatment of left and right handed charged leptons on the same footing. We have optimized the free parameters of our models in order to match the experimental data, obtaining a good degree of compatibility and predictions for the absolute neutrino masses and the $CP$ violating phases. At a more fundamental level, the whole lepton sector could be correctly described by the simultaneous presence of several moduli. Our examples are meant to make a first step in this direction.

  • Flavoured leptogenesis and ${\rm CP}^{\mu\tau}$ symmetry
    JHEP 2001 (2020) 193

    by: Samanta, Rome (Southampton U.) et al.

    We present a systematic study of leptogenesis in neutrino mass models with $\mu\tau$-flavoured CP symmetry. In addition to the strong hierarchical $N_1$-dominated scenario ($N_1$DS) in the `two flavour regime' of leptogenesis, we show that one may choose the right-handed (RH) neutrino mass hierarchy as mild as $M_2\simeq 4.7 M_1$ for a perfectly valid hierarchical $N_1$DS. This in turn reduces the lower bound on the allowed values of $M_1$, compared to what is stated in the literature. The consideration of flavour effects due to the heavy neutrinos also translate into an upper bound on $M_1$. It is only below this bound that the observed baryon-to-photon ratio can be realized for a standard ${ N_1}$ domination, else a substantial part of the parameter space is also compatible with $N_2$DS. We deduce conditions under which the baryon asymmetry produced by the second RH neutrino plays an important role. Finally, we discuss another interesting scenario where lepton asymmetry generated by $N_2$ in the two flavour regime faces washout by $N_1$ in the three flavour regime. Considering a hierarchical light neutrino mass spectrum, which is now favoured by cosmological observations, we show that at the end of $N_1$-leptogenesis, the asymmetry generated by $N_2$ survives only in the electron flavour and around $33\%$ of the parameter space is consistent with a pure $N_2$-leptogenesis.

  • Testing the Seesaw Mechanism and Leptogenesis with Gravitational Waves
    DESY 19-138
    Phys.Rev.Lett. 124 (2020) 041804

    by: Dror, Jeff A. (UC, Berkeley) et al.

    We present the possibility that the seesaw mechanism with thermal leptogenesis can be tested using the stochastic gravitational background. Achieving neutrino masses consistent with atmospheric and solar neutrino data, while avoiding nonperturbative couplings, requires right handed neutrinos lighter than the typical scale of grand unification. This scale separation suggests a symmetry protecting the right-handed neutrinos from getting a mass. Thermal leptogenesis would then require that such a symmetry be broken below the reheating temperature. We enumerate all such possible symmetries consistent with these minimal assumptions and their corresponding defects, finding that in many cases, gravitational waves from the network of cosmic strings should be detectable. Estimating the predicted gravitational wave background, we find that future space-borne missions could probe the entire range relevant for thermal leptogenesis.

  • Zee-Burst: A New Probe of Neutrino Non-Standard Interactions at IceCube
    Phys.Rev.Lett. 124 (2020) 041805

    by: Babu, K.S. (Oklahoma State U.) et al.

    We propose a new way to probe nonstandard interactions (NSI) of neutrinos with matter using the ultrahigh energy (UHE) neutrino data at current and future neutrino telescopes. We consider the Zee model of radiative neutrino mass generation as a prototype, which allows two charged scalars—one SU(2)L doublet and one singlet, both being leptophilic, to be as light as 100 GeV, thereby inducing potentially observable NSI with electrons. We show that these light charged Zee scalars could give rise to a Glashow-like resonance feature in the UHE neutrino event spectrum at the IceCube neutrino observatory and its high-energy upgrade IceCube-Gen2, which can probe a sizable fraction of the allowed NSI parameter space.

  • Detecting and Studying High-Energy Collider Neutrinos with FASER at the LHC
    SLAC-PUB-17460, UCI-TR-2019-19
    Eur.Phys.J. C80 (2020) 61

    by: Abreu, Henso (Technion) et al.

    Neutrinos are copiously produced at particle colliders, but no collider neutrino has ever been detected. Colliders, and particularly hadron colliders, produce both neutrinos and anti-neutrinos of all flavors at very high energies, and they are therefore highly complementary to those from other sources. FASER, the recently approved Forward Search Experiment at the Large Hadron Collider, is ideally located to provide the first detection and study of collider neutrinos. We investigate the prospects for neutrino studies of a proposed component of FASER, FASER$\nu$, a 25cm x 25cm x 1.35m emulsion detector to be placed directly in front of the FASER spectrometer in tunnel TI12. FASER$\nu$ consists of 1000 layers of emulsion films interleaved with 1-mm-thick tungsten plates, with a total tungsten target mass of 1.2 tons. We estimate the neutrino fluxes and interaction rates at FASER$\nu$, describe the FASER$\nu$ detector, and analyze the characteristics of the signals and primary backgrounds. For an integrated luminosity of 150 fb$^{-1}$ to be collected during Run 3 of the 14 TeV Large Hadron Collider from 2021-23, and assuming standard model cross sections, approximately 1300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos will interact in FASER$\nu$, with mean energies of 600 GeV to 1 TeV, depending on the flavor. With such rates and energies, FASER will measure neutrino cross sections at energies where they are currently unconstrained, will bound models of forward particle production, and could open a new window on physics beyond the standard model.

  • Viable secret neutrino interactions with ultralight dark matter
    Phys.Lett. B802 (2020) 135182

    by: Cline, James M. (McGill U., Montreal (main))

    Several anomalies in neutrino oscillation experiments point to the existence of a $\sim 1\,$eV sterile neutrino $\nu_s$ mixing with $\nu_e$ at the level of $U_{e4}\cong 0.1$, but such a neutrino is strongly disfavored by constraints on additional light degrees of freedom ($\delta N_{\rm eff}$) and total neutrino mass ($\sum_\nu m_\nu$) from cosmology. "Secret neutrino interactions" that have been invoked to suppress the cosmological production of $\nu_s$ typically falter, but recently it was pointed out that $\nu_s$ could get a large mass in the early universe by coupling to ultralight dark matter $\phi$, which can robustly suppress its production. The model has essentially two free parameters: $m_\phi$, and $m_{s,0}$, the mass of the sterile neutrino at early times, enhanced by its coupling to $\phi$. I determine the parameter regions allowed by limits on $\delta N_{\rm eff}$ and $\sum_\nu m_\nu$ from the cosmic microwave background and big bang nucleosynthesis, using a simplified yet accurate treatment of neutrino oscillations in the early universe. This mechanism could have an important impact on laboratory experiments that suggest oscillations with sterile neutrinos.

  • Neutrino counting experiments and non-unitarity from LEP and future experiments
    Phys.Lett. B802 (2020) 135241

    by: Escrihuela, F.J. (Valencia U., IFIC) et al.

    Non-unitarity of the neutrino mixing matrix is expected in many scenarios with physics beyond the Standard Model. Motivated by the search for deviations from unitary, we study two neutrino counting observables: the neutrino-antineutrino gamma process and the invisible Z boson decay into neutrinos. We report on new constraints for non-unitarity coming from the first of these observables. We study the potential constraints that future collider experiments will give from the invisible decay of the Z boson, that will be measured with improved precision.

  • Radiative neutrino model with semi-annihilation dark matter
    Phys.Rev. D101 (2020) 035006

    by: Cai, Haiying (APCTP, Pohang)

    We propose a two-loop induced radiative neutrino model with hidden gauged U(1) symmetry, in which dark matter of Dirac fermions arises. The relic density gets a contribution from annihilation and semiannihilation due to a residual Z3 parity. After imposing the requirement of neutrino oscillation data and lepton flavor violation bounds, we find that semiannihilation plays a crucial role in order to satisfy the relic density constraint 0.117<Ωh2<0.123, by proceeding near either one of two deconstructive scalar resonances. Our numerical analysis demonstrates the allowed region for the DM-scalar coupling with the DM mass in (80, 400) GeV.

  • Gravitational and Chiral Anomalies in the Running Vacuum Universe and Matter-Antimatter Asymmetry
    Phys.Rev. D101 (2020) 045001

    by: Basilakos, Spyros (RCAAM, Academy of Athens) et al.

    We present a model for the Universe in which quantum anomalies are argued to play an important dual role: they are responsible for generating matter-antimatter asymmetry in the cosmos, but also provide time-dependent contributions to the vacuum energy density of “running-vacuum” type, which drive the Universe’s evolution. According to this scenario, during the inflationary phase of a string-inspired Universe, and its subsequent exit, the existence of primordial gravitational waves induces gravitational anomalies, which couple to the [Kalb-Ramond (KR)] axion field emerging from the antisymmetric tensor field of the massless gravitational multiplet of the string. Such anomalous CP-violating interactions have two important effects. First, they lead to contributions to the vacuum energy density of the form appearing in the “running vacuum model” (RVM) framework, which are proportional to both, the square and the fourth power of the effective Hubble parameter, H2 and H4 respectively. The H4 terms may lead to inflation, in a dynamical scenario whereby the role of the inflaton is played by the effective scalar-field (“vacuumon”) representation of the RVM. Second, there is an undiluted KR axion at the end of inflation, which plays an important role in generating matter-antimatter asymmetry in the cosmos, through baryogenesis via leptogenesis in models involving heavy right-handed neutrinos. As the Universe exits inflation and enters a radiation-dominated era, the generation of chiral fermionic matter is responsible for the cancellation of gravitational anomalies, thus restoring diffeomorphism invariance for the matter/radiation (quantum) theory, as required for consistency. Chiral U(1) anomalies may remain uncompensated, though, during matter/radiation dominance, providing RVM-like H2 and H4 contributions to the Universe energy density. Finally, in the current era, when the Universe enters a de Sitter phase again, and matter is no longer dominant, gravitational anomalies resurface, leading to RVM-like H2 contributions to the vacuum energy density, which are however much more suppressed, as compared to their counterparts during inflation, due to the smallness of the present era’s Hubble parameter H0. In turn, this feature endows the observed dark energy with a dynamical character that follows the RVM pattern, a fact which has been shown to improve the global fits to the current cosmological observations as compared to the concordance ΛCDM model with its rigid cosmological constant, Λ>0. Our model favors axionic dark matter, the source of which can be the KR axion. The uncompensated chiral anomalies in late epochs of the Universe are argued to play an important role in this, in the context of cosmological models characterized by the presence of large-scale cosmic magnetic fields at late eras.

  • Predictions for the neutrino parameters in the minimal model extended by linear combination of U(1)$_{L_e-L_\mu}$, U(1)$_{L_\mu-L_\tau}$ and U(1)$_{B-L}$ gauge symmetries
    Eur.Phys.J. C80 (2020) 76

    by: Asai, Kento (Tokyo U.)

    We study the minimal extensions of the Standard Model by a linear combination of U(1)$_{L_e-L_\mu}$, U(1)$_{L_\mu-L_\tau}$ and U(1)$_{B-L}$ gauge symmetries, where three right-handed neutrinos and one U(1)-breaking SU(2)$_L$ singlet or doublet scalar are introduced. Because of the dependence on the lepton flavor, the structures of both Dirac and Majorana mass matrices of neutrinos are restricted. In particular, the two-zero minor and texture structures in the mass matrix for the active neutrinos are interesting. Analyzing these structures, we obtain uniquely all the neutrino parameters, namely the Dirac CP phase $\delta$, the Majorana CP phases $\alpha_{2,3}$ and the mass eigenvalues of the light neutrinos $m_i$ as functions of the neutrino mixing angles $\theta_{12}$, $\theta_{23}$, and $\theta_{13}$, and the squared mass differences $\Delta m^2_{21}$ and $\Delta m^2_{31}$. In 7 minimal models which are consistent with the recent neutrino oscillation data, we also obtain the predictions for the sum of the neutrino masses $\Sigma_i m_i$ and the effective Majorana neutrino mass $\langle m_{\beta \beta} \rangle$ and compare them with the current experimental limits. In addition, we also discuss the implication of our results for leptogenesis.

  • Probing Non-Standard Neutrino Interactions with Supernova Neutrinos at Hyper-K
    JHEP 2001 (2020) 179

    by: Lei, Minjie (Michigan U., MCTP) et al.

    Non-standard neutrino self interactions (NSSI) could be stronger than Fermi interactions. We investigate the ability to constrain these four-neutrino interactions by their effect on the flux of neutrinos originating from a galactic supernova. In the dense medium of a core collapse supernova, these new self interactions can have a significant impact on neutrino oscillations, leading to changes at the flavor evolution and spectra level. We use simulations of the neutrino flux from a 13 solar mass, core collapse supernova at 10 kpc away, and numerically propagate these neutrinos through the stellar medium taking into account vacuum/MSW oscillations, SM $\nu-\nu$ scattering as well as $\nu-\nu$ interactions that arise from NSSI. We pass the resulting neutrino flux to a simulation of the future Hyper-Kamiokande detector to see what constraints on NSSI parameters are possible when the next galactic supernova becomes visible. We find that these constraints depend strongly on the neutrino mass hierarchy and if the NSSI is flavor-violating or preserving. Sensitivity to NSSI in the normal hierarchy (NH) at Hyper-K is limited by the experiment's ability to efficiently detect $\nu_{e}$, but deviations from no NSSI could be seen if the NSSI is particularly strong. In the inverted hierarchy (IH) scenario, Hyper-K can significantly improve constraints on flavor-violating NSSI down to $\mathcal{O}(10^{-1})G_{F}$.

  • Study of a tri-direct littlest seesaw model at MOMENT
    Nucl.Phys. B952 (2020) 114915

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

    The flavour symmetry succeeds in explaining the current global fit results. Flavour-symmetry models can be tested by the future experiments that improve the precision of neutrino oscillation parameters, \textit{such as} the MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). In this work, we consider tri-direct littlest seesaw (TDLS) models for a case study, and analyze how much MOMENT can extend our knowledge on the TDLS model. We find that measurements of $\theta_{23}$ and $\delta$ are crucial for MOMENT to exclude the model at more than $5\sigma$ confidence level, if the best fit values in the last global analysis result is confirmed. Moreover, the $3\sigma$ precision of model parameters can be improved at MOMENT by at least a factor of two. Finally, we project the surface at the $3\sigma$ confidence level from the model-parameter space to the oscillation-parameter space, and find the potential of MOMENT to observe the sum rule between $\theta_{23}$ and $\delta$ predicted by TDLS.

  • Neutrino decoherence in presence of strong gravitational fields
    Phys.Lett. B801 (2020) 135150

    by: Chatelain, Amélie (APC, Paris) et al.

    We explore the impact of strong gravitational fields on neutrino decoherence. To this aim, we employ the density matrix formalism to describe the propagation of neutrino wave packets in curved spacetime. By considering Gaussian wave packets, we determine the coherence proper time, neglecting the effect of matter outside the compact object. We show that strong gravitational fields nearby compact objects significantly influence neutrino coherence.

  • Neutrino flavor oscillations and spin rotation in matter and electromagnetic field
    Phys.Rev. D101 (2020) 013003

    by: Chukhnova, A.V. (Moscow State U.) et al.

    We obtain a relativistically covariant wave equation for neutrinos in dense matter and electromagnetic field, which describes both flavor oscillations and neutrino spin rotation. Using this equation we construct a quasiclassical theory of these phenomena. We obtain the probabilities of arbitrary spin-flavor transitions assuming the external conditions to be constant. We demonstrate that the resonance behavior of the transition probabilities is possible only when the neutrino flavor states cannot be described as superpositions of the mass eigenstates. We discover that a resonance, which is similar to the Mikheev–Smirnov–Wolfenstein resonance, takes place for neutrinos in magnetic field due to the transition magnetic moments. This resonance gives an opportunity to determine, whether neutrinos are Dirac or Majorana particles.

  • Exploring CP-Violating heavy neutrino oscillations in rare tau decays at Belle II
    Nucl.Phys. B952 (2020) 114936

    by: Tapia, Sebastian (Illinois U., Urbana) et al.

    In this work, we study the lepton number violating tau decays via two intermediate on-shell Majorana neutrinos $N_j$ into two charged pions, and a charged lepton $\tau^{\pm} \to \pi^{\pm} N_j \to \pi^{\pm} \pi^{\pm} \ell^{\mp}$. We consider the scenario where the heavy neutrino masses are within $0.5$ GeV $\leq M_N \leq 1.5$ GeV. We evaluated the possibility to measure the modulation of the decay width along the detector length for these processes at taus factories, such as Belle II. We study some realistic conditions which could lead to the observation of this phenomenon at futures $\tau$'s factories.

  • Triplet Leptogenesis, Type-II Seesaw Dominance, Intrinsic Dark Matter, Vacuum Stability and Proton Decay in Minimal SO(10) Breakings
    JCAP 2001 (2020) 049

    by: Chakraborty, Mainak (Siksha O Anusandhan U., Bhubaneswar) et al.

    We implement type-II seesaw dominance for neutrino mass and baryogenesis through heavy scalar triplet leptogenesis in a class of minimal non-supersymmetric SO(10) models where matter parity as stabilising discrete symmetry as well as WIMP dark matter (DM) candidates are intrinsic predictions of the GUT symmetry. We also find modifications of relevant CP-asymmetry formulas in such models. Baryon asymmetry of the universe as solutions of Boltzmann equations is further shown to be realized for both normal and inverted mass orderings in concordance with cosmological bound and best fit values of the neutrino oscillation data including θ23 in the second octant and large values of leptonic Dirac CP-phases. Type-II seesaw dominance is at first successfully implemented in two cases of spontaneous SO(10) breakings through SU(5) route where the presence of only one non-standard Higgs scalar of intermediate mass ∼ 109−1010 GeV achieves unification. Lower values of the SU(5) unification scales ∼ 1015 GeV are predicted to bring proton lifetimes to the accessible ranges of Super-Kamiokande and Hyper-Kamiokande experiments. Our prediction of WIMP DM relic density in each model is due to a ∼ &calO; (1) TeV mass matter-parity odd real scalar singlet (⊂ 16H ⊂ SO(10)) verifiable by LUX and XENON1T experiments. This DM is also noted to resolve the vacuum stability issue of the standard scalar potential. When applied to the unification framework of M. Frigerio and T. Hambye, in addition to the minimal fermionic triplet DM solution of 2.7 TeV, our mechanism of type-II seesaw dominance and triplet leptogenesis is also found to make an alternative prediction of the triplet fermion plus the real scalar singlet DM near the TeV scale.

  • An Axion-Like Particle from an $SO(10)$ Seesaw with $U(1)_X$
    Phys.Lett. B802 (2020) 135273

    by: Corianò, Claudio (Salento U.) et al.

    We investigate the decoupling of heavy right handed neutrinos in the context of an SO(10) GUT model, where a remnant anomalous symmetry is $U(1)_{X}$. In this model the see-saw mechanism which generates the neutrino masses is intertwined with the Stueckelberg mechanism, which leaves the CP-odd phase of a very heavy Higgs in the low energy spectrum as an axion-like particle. Such pseudoscalar is predicted to be ultralight, in the $10^{-20}$ eV mass range. In this scenario, the remnant anomalous $X$ symmetry of the particles of the Standard Model is interpreted as due to the incomplete decoupling of the right handed neutrino sector. We illustrate this scenario including its realisation in the context of SO(10).

  • A low scale type I seesaw model for lepton masses and mixings
    Phys.Rev. D101 (2020) 035005

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

    In contrast to the original type I seesaw mechanism that requires right-handed Majorana neutrinos at energies much higher than the electroweak scale, the so-called low scale seesaw models allow lighter masses for the additional neutrinos. Here we propose an alternative low scale type I seesaw model, where neither linear nor inverse seesaw mechanisms take place, but the spontaneous breaking of a discrete symmetry at an energy scale much lower than the model cutoff is responsible for the smallness of the light active neutrino masses. In this scenario, the model is defined with minimal particle content, where the right-handed Majorana neutrinos can have masses at the ∼50  GeV scale. The model is predictive in the neutrino sector having only four effective parameters that allow to successfully reproduce the experimental values of the six low energy neutrino observables.

  • Impact of Cross-Sectional Uncertainties on DUNE Sensitivity due to Nuclear Effects
    Nucl.Phys. B951 (2020) 114888

    by: Nagu, Srishti (Lucknow U.) et al.

    In neutrino oscillation experiments precise measurement of neutrino oscillation parameters is of prime importance as well as a challenge. To improve the statistics, presently running and proposed experiments are using heavy nuclear targets. These targets introduce nuclear effects and the quantification of these effects on neutrino oscillation parameters will be decisive in the prediction of neutrino oscillation physics. Limited understanding of neutrino nucleus interactions and inaccurate reconstruction of neutrino energy causes uncertainty in the cross section. The error in the determination of cross section which contributes to systematic error introduces error in the neutrino mixing parameters that are determined by these experiments. In this work we focus on the variation in the predictions of DUNE potential, arising due to systematic uncertainties, using two different event generators-GENIE and GiBUU. These generators have different and independent cross-section models. To check the DUNE potential with the two generators we have checked the sensitivity studies of DUNE for CP violation, mass hierarchy and octant degeneracy.

  • Pre-Supernova Neutrinos in Large Dark Matter Direct Detection Experiments
    Phys.Rev. D101 (2020) 043008

    by: Raj, Nirmal (TRIUMF) et al.

    The next Galactic core-collapse supernova (SN) is a highly anticipated observational target for neutrino telescopes. However, even prior to collapse, massive dying stars shine copiously in 'pre-supernova' (pre-SN) neutrinos, which can potentially act as efficient SN warning alarms and provide novel information about the very last stages of stellar evolution. We explore the sensitivity to pre-SN neutrinos of large scale direct dark matter detection experiments, which, unlike dedicated neutrino telescopes, take full advantage of coherent neutrino-nucleus scattering. We find that argon-based detectors with target masses of $\mathcal{O}(100)$ tonnes (i.e. comparable in size to the proposed ARGO experiment) can detect $\mathcal{O}(10-100)$ pre SN neutrinos coming from a source at a characteristic distance of $\sim$200 pc, such as Betelgeuse ($\alpha$ Orionis). For such a source, large scale dark matter experiments could provide a SN warning siren $\sim$10 hours prior to the explosion. We also comment on the complementarity of large scale direct dark matter detection experiments and neutrino telescopes in the understanding of core-collapse SN.

  • Constraints on Non-Standard Neutrino Interactions from Borexino Phase-II

    JHEP 2002 (2020) 038

    by: Agarwalla, S.K. (Bhubaneswar, Inst. Phys.) et al.

    The Borexino detector measures solar neutrino fluxes via neutrino-electron elastic scattering. Observed spectra are determined by the solar-$\nu_{e}$ survival probability $P_{ee}(E)$, and the chiral couplings of the neutrino and electron. Some theories of physics beyond the Standard Model postulate the existence of Non-Standard Interactions (NSI's) which modify the chiral couplings and $P_{ee}(E)$. In this paper, we search for such NSI's, in particularly neutral-current-like interactions that modify the $\nu_e - e$ and $\nu_\tau - e$ couplings, using Borexino Phase II data. Standard Solar Model predictions of the solar neutrino fluxes for both high- and low-metallicity assumptions are considered. No indication of new physics is found at the level of sensitivity of the detector and constraints on the parameters of the NSI's are placed. In addition, with the same dataset the value of $\sin^2\theta_W$ is obtained with a precision comparable to that achieved in reactor antineutrino experiments.

  • Distinguishing Dirac and Majorana neutrinos by their decays via Nambu-Goldstone bosons in the gravitational-anomaly model of neutrino masses
    Phys.Rev. D101 (2020) 015025

    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, νi→νj+ϕ and νi→ν¯j+ϕ, where the gravi-Majorons ϕ 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 particular, we put bounds on the neutrino lifetimes in the Majorana case, τ2/m2>1.1×10-3(6.7×10-4)  s/eV and τ3/m3>2.2×10-5(1.3×10-4)  s/eV at 90% CL for hierarchical (degenerate) masses, using data from experiments searching for antineutrino appearance from the Sun.

  • Measuring dark matter-neutrino relative velocity on cosmological scales
    Phys.Rev. D101 (2020) 023525

    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 that the minimal sum of neutrino masses could be detected at high significance with upcoming surveys.

  • Migdal effect and photon bremsstrahlung in effective field theories of dark matter direct detection and coherent elastic neutrino-nucleus scattering
    Phys.Rev. D101 (2020) 015012

    by: Bell, Nicole F. (Melbourne U.) 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 O(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 bremsstrahlung 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.

  • High energy muons in extensive air showers
    JCAP 2001 (2020) 057

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

    The production of very high energy muons inside an extensive air shower is observable at ν 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/ψ vector meson decaying into muons. We solve the cascade equations for a 1010.5 GeV proton primary and find that unflavored mesons and gamma conversions are the two main sources of E≥ 108.5 GeV muons, while charm decays dominate at 105.5 GeV< E< 108.5 GeV. In inclined events one of these muons may deposite a large fraction of its energy near the surface, implying fluctuations 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 6 proton showers of 1010.5 GeV include an E>106 GeV deposition within 500 g/cm2, while only in 1 out of 330 showers it is above 107 GeV . We also show that the production of high energy muons is very different in proton, iron or photon showers (e.g., conversions γ&to; μ+ μ− are the main source of E≥ 104 GeV muons in photon showers). Finally, we use Monte Carlo simulations to discuss the validity of our results.

  • Low-scale seesaw from neutrino condensation
    Nucl.Phys. B952 (2020) 114910

    by: Dib, Claudio (CCTVal, Valparaiso) et al.

    Knowledge of the mechanism of neutrino mass generation would help understand a lot more about Lepton Number Violation (LNV), the cosmological evolution of the Universe, or the evolu tion of astronomical objects. Here we propose a verifiable and viable extension of the Standard model for neutrino mass generation, with a low-scale seesaw mechanism via LNV condensation in the sector of sterile neutrinos. To prove the concept, we analyze a simplified model of just one single family of elementary particles and check it against a set of phenomenological constraints coming from electroweak symmetry breaking, neutrino masses, leptogenesis and dark matter. The model predicts (i) TeV scale quasi-degenerate heavy sterile neutrinos, suitable for leptogenesis with resonant enhancement of the CP asymmetry, (ii) a set of additional heavy Higgs bosons whose existence can be challenged at the LHC, (iii) an additional light and sterile Higgs scalar which is a candidate for decaying warm dark matter, and (iv) a majoron. Since the model is based on simple and robust principles of dynamical mass generation, its parameters are very restricted, but remarkably it is still within current phenomenological limits.

  • Heavy Neutrinos in displaced vertex searches at the LHC and HL-LHC
    JHEP 2002 (2020) 070
    JHEP 2020 (2020) 070

    by: Drewes, Marco (Southern Denmark U., CP3-Origins) et al.

    We study the sensitivity of displaced vertex searches for heavy neutrinos produced in W boson decays in the LHC detectors ATLAS, CMS and LHCb. We also propose a new search that uses the muon chambers to detect muons from heavy neutrino decays outside the tracker. The sensitivity estimates are based on benchmark models in which the heavy neutrinos mix exclusively with one of the three Standard Model generations. In the most sensitive mass regime the displaced vertex searches can improve existing constraints on the mixing with the first two SM generations by more than four orders of magnitude and by three orders of magnitude for the mixing with the third generation.

  • Can Oscillating Neutrino States Be Formulated Universally?
    Eur.Phys.J. C80 (2020) 68

    by: Tureanu, Anca (Helsinki U.)

    A standing problem in neutrino physics is the consistent and universal definition of oscillating neutrino states as coherent superpositions of massive neutrino states. This problem is solved in a quantum field theoretical framework of neutrino mixing developed in analogy with the Nambu--Jona-Lasinio model for the dynamical generation of nucleon masses. The massive neutrino states are Bogoliubov quasiparticles and their vacuum is a condensate of "Cooper pairs" of massless flavour neutrinos. Their superpositions as oscillating neutrino states have intrinsic quantum coherence by construction. In this quantization framework, the standard phenomenological flavour neutrino states and oscillation probability formula are validated in the ultrarelativistic approximation.

  • Solar neutrino problem as evidence of new interaction
    Sov.Phys.JETP 129 (2019) 973-984

    by: Slad, L.M. (SINP, Moscow)

    A new concept is proposed to solve the solar neutrino problem, that is based on a hypothesis about the existence of a new interaction of electron neutrinos with nucleons mediated by massless pseudoscalar bosons. At every collision of a neutrino with nucleons of the Sun, its handedness changes from left to right and vice versa, and its energy decreases. The postulated hypothesis, having only one free parameter, provides a good agreement between the calculated and experimental characteristics of all five observed processes with solar neutrinos.

  • Charged lepton beams as a source of effective neutrinos
    EPL 129 (2020) 11003

    by: Alikhanov, I. (Moscow, INR)

    Neutrinos are likely the most poorly understood basic constituents of the Standard Model. In order to investigate precisely their interactions one should be able to create high intensity and well-collimated neutrino beams with known flavor compositions. This is a challenging problem for neutrino experiments. We propose a method of studying neutrino interactions based on the fact that a charged lepton is able to manifest itself effectively, with a certain probability, as a neutrino. The effective neutrino method may provide an additional tool for probing neutrino-induced reactions at $e^+e^-$ and $ep$ colliders as well as at other facilities that use charged lepton beams. We derive the distributions of the effective neutrinos in the charged leptons and give examples of application of the method to electron-positron collisions.

  • $SU(5)$ grand unified theory with $A_4$ modular symmetry
    Phys.Rev. D101 (2020) 015028

    by: de Anda, Francisco J. (Tepatitlan's Inst. Theor. Studies) et al.

    We present the first example of a grand unified theory (GUT) with a modular symmetry interpreted as a family symmetry. The theory is based on supersymmetric $SU(5)$ in 6d, where the two extra dimensions are compactified on a $T_2/\mathbb{Z}_2$ orbifold, with a twist angle of $\omega=e^{i2\pi/3}$. Such constructions suggest an underlying modular $A_4$ symmetry with fixed modulus $\tau = \omega=e^{i2\pi/3}$. The fields on the branes respect a generalised CP and flavour symmetry $A_4\ltimes \mathbb{Z}_2$ which leads to an effective $\mu-\tau$ reflection symmetry at low energies, implying maximal atmospheric mixing and maximal leptonic CP violation. We construct an explicit model along these lines with two triplet flavons in the bulk, whose vacuum alignments are determined by orbifold boundary conditions, analogous to those used for $SU(5)$ breaking with doublet-triplet splitting. There are two right-handed neutrinos on the branes whose Yukawa couplings are determined by modular weights. The charged lepton and down-type quarks have diagonal and hierarchical Yukawa matrices, with quark mixing due to a hierarchical up-quark Yukawa matrix with high modular weight to provide quark CP violation.

  • The Effect of the Earth Matter on Three Neutrino Oscillations and Sensitivity to CP Phase Parameter
    Eur.Phys.J.Plus 135 (2020) 94

    by: Shafaq, Bushra (Punjab U., CHEP) et al.

    We find an analytical expression of neutrino evolution operator in the Earth matter using perturbative approach in the context of three neutrino oscillations. We find our analytical expression highly accurate, by comparing its results with the numerical solutions of neutrino evolution equation at energy scales relevant for solar, reactor, atmospheric, and accelerator neutrinos. By applying two different models of Earth density, we find that 2-neutrino approximation provide systematic errors similar or larger to the one given by the uncertainty in the Earth Model. We also study how the Earth matter effect can change the sensitivity to CP phase parameter $\delta _{\text {CP}}$. Through nadir angle averaged conversion probabilities of neutrino and anti-neutrino, we find that the sensitivity to $\delta _{\text {CP}}$ is maximum in the energy range 0.2–1 GeV and through energy averaged conversion probabilities, we find that the sensitivity is maximum about nadir angle $72.5^{\circ }$ for neutrinos oscillating in the Earth matter.

  • Weak neutral current axial form factor using $ \left(\overline{\nu}\right)\nu $-nucleon scattering and lattice QCD inputs
    JHEP 2001 (2020) 136

    by: Sufian, Raza Sabbir (Jefferson Lab) et al.

    We present a determination of the neutral current weak axial charge $ {G}_A^Z(0)=-0.654{(3)}_{\mathrm{stat}}{(5)}_{\mathrm{sys}} $ using the strange quark axial charge $ {G}_A^s(0) $ calculated with lattice QCD. We then perform a phenomenological analysis, where we combine the strange quark electromagnetic form factor from lattice QCD with (anti)neutrino-nucleon scattering differential cross section from MiniBooNE experiments in a momentum transfer region 0.24 ≲ Q$^{2}$ ≲ 0.71 GeV$^{2}$ to determine the neutral current weak axial form factor $ {G}_A^Z\left({Q}^2\right) $ in the range of 0 ≲ Q$^{2}$ ≤ 1 GeV$^{2}$. This yields a phenomenological value of $ {G}_A^Z(0) $ = −0.687(89)$_{stat}$(40)$_{sys}$. The value of $ {G}_A^Z(0) $ constrained by the lattice QCD calculation of $ {G}_A^s(0) $, when compared to its phenomenological determination, provides a significant improvement in precision and accuracy and can be used to provide a constraint on the fit to $ {G}_A^Z\left({Q}^2\right) $ for Q$^{2}$> 0. This constrained fit leads to an unambiguous determination of (anti)neutrino-nucleon neutral current elastic scattering differential cross section near Q$^{2}$ = 0 and can play an important role in numerically isolating nuclear effects in this region. We show a consistent description of $ {G}_A^Z\left({Q}^2\right) $ obtained from the (anti)neutrino-nucleon scattering cross section data requires a nonzero contribution of the strange quark electromagnetic form factor. We demonstrate the robustness of our analysis by providing a post-diction of the BNL E734 experimental data.

  • Modeling neutrino-nucleus interaction at intermediate energies
    PoS NuFact2017 (2017) 072

    by: González-Jiménez, Raul (Gent U.) et al.

    We present the current status of the research activities of the Ghent group on neutrino-nucleus interactions. These consist in the modeling of some of the relevant neutrino-nucleus reaction channels at intermediate energies: low-energy nuclear excitations, quasielastic scattering, two-nucleon knockout processes and single-pion production. The low-energy nuclear excitations and the quasielastic peak are described using a Hartree-Fock-CRPA (continuum random phase approximation) model that takes into account nuclear long-range correlations as well as the distortion of the outgoing nucleon wave function. We include two-body current mechanisms through short-range correlations and meson-exchange currents. Their influence on one- and two-nucleon knockout responses is computed. Bound and outgoing nucleons are treated within the same mean-field framework. Finally, for modeling of the neutrino-induced single-pion production, we use a low-energy model that contains resonances and the background contributions required by chiral symmetry. This low-energy model is combined with a Regge approach into a Hybrid model, which allows us to make predictions beyond the resonance region.

  • On the MSW neutrino mixing effects in atomic weak interactions and double beta decays
    Eur.Phys.J. A56 (2020) 39

    by: Horoi, Mihai (Central Michigan U.)

    Matter effects on the mixing of the neutrinos mass eigenstates, also know as the Mikheyev-Smirnov-Wolfenstein effect, seem to be well established in describing the propagation of the neutrino from the source to detecting devices. These effects were mostly considered in bulk matter, but not inside the atoms. Here we consider the effect of the high electron densities existing in the atomic nuclei. We investigate if these effects can affect the known neutrino phenomenology. It was reported that the mixing of the neutrino in high density matter, such as inside a supernova, can affect the Majoron decay probabilities. We investigate if the neutrino mixing effects in the high electron density inside the atomic nuclei can change the neutrinoless double beta decay half-life formula. In both cases we found that the standard results stand. The results look simple, but the road to them is complex and it opens the possibility that the neutrino mixing in atomic nuclei may affect other observables, such as the neutrinoless double beta Majoron decays.

  • A quantum information theoretic quantity sensitive to the neutrino mass-hierarchy
    Nucl.Phys. B951 (2020) 114872

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

    In this work, we derive a quantum information theoretic quantity similar to the Leggett-Garg inequality, which can be defined in terms of neutrino transition probabilities. For the case of νμ→νe/ν¯μ→ν¯e transitions, this quantity is sensitive to CP violating effects as well as the neutrino mass-hierarchy, namely which neutrino mass eigenstate is heavier than the other ones. The violation of the inequality for this quantity shows an interesting dependence on mass-hierarchy. For normal (inverted) mass-hierarchy, it is significant for νμ→νe ( ν¯μ→ν¯e ) transitions. This is applied to the two ongoing accelerator experiments T2K and NO ν A as well as the future experiment DUNE.

  • Relating quantum mechanics and kinetics of neutrino ascillations
    JHEP 2001 (2020) 138

    by: Kartavtsev, Alexander (Yaroslavl State U.)

    Simultaneous treatment of neutrino oscillations and collisions in astrophysical environments requires the use of (quantum) kinetic equations. Despite major advances in the field of quantum kinetics, the structure of the kinetic equations and their consistency with the uncertainty principle are still debated. The goals of the present work are threefold. First, it clarifies the structure of the Liouville term in the presence of mixing. Second, we derive evolution equation for neutrinos propagating in vacuum or matter from the Schrödinger equation and show that in the relativistic limit its form matches the form of the (collisionless part of the) kinetic equation derived by Sigl and Raffelt. Third, by constructing solutions of the evolution equation from the known solutions of the Schrödinger equation, we show that the former also admits solutions consistent with the uncertainty principle and accounts for neutrino wave packet separation. The obtained results speak in favor of a (quantum) kinetic approach to the analysis of neutrino propagation in exploding supernovae where neutrino oscillations and collisions, as well as the effect of wave packet separation, might be equally important.

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