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  • Proceedings, New Trends in High-Energy Physics: Odessa, Odessa, Ukraine, May 12-18, 2019
    Ukr.J.Phys. 64 (2019)

  • Neutrino oscillations in gravitational waves

    by: Dvornikov, Maxim
    We study spin and flavor oscillations of neutrinos under the influence of gravitational waves (GWs). We rederive the quasiclassical equation for the evolution of the neutrino spin in various external fields in curved spacetime starting from the Dirac equation for a massive neutrino. Then, we consider neutrino spin oscillations in nonmoving and unpolarized matter, a transverse magnetic field, and a plane GW. We show that a parametric resonance can take place in this system. We also study neutrino flavor oscillations in GWs. The equation for the density matrix of flavor neutrinos is solved when we discuss the neutrino interaction with stochastic GWs emitted by coalescing supermassive black holes. We find the fluxes of cosmic neutrinos, undergoing flavor oscillations in such a gravitational background, which can be potentially measured by a terrestrial detector. Some astrophysical applications of our results are considered.

  • On the Impact of Neutrino Decays on the Supernova Neutronization-Burst Flux

    by: de Gouvêa, André
    The discovery of non-zero neutrino masses invites one to consider decays of heavier neutrinos into lighter ones. We investigate the impact of two-body decays of neutrinos on the neutronization burst of a core-collapse supernova -- the large burst of $\nu_e$ during the first 25 ms post core-bounce. In the models we consider, the $\nu_e$, produced mainly as a $\nu_3\,(\nu_2)$ in the normal (inverted) mass ordering, are allowed to decay to $\nu_1\,(\nu_3)$ or $\bar{\nu}_1\,(\bar{\nu}_3)$, and an almost massless scalar. These decays can lead to the appearance of a neutronization peak for a normal mass ordering or the disappearance of the same peak for the inverted one, thereby allowing one mass ordering to mimic the other. Simulating supernova-neutrino data at the Deep Underground Neutrino Experiment (DUNE) and the Hyper-Kamiokande (HK) experiment, we compute their sensitivity to the neutrino lifetime. We find that, if the mass ordering is known, and depending on the nature of the Physics responsible for the neutrino decay, DUNE is sensitive to lifetimes $\tau/m \lesssim 10^6$ s/eV for a galactic SN sufficiently close-by (around 10 kpc), while HK is sensitive to lifetimes $\tau/m \lesssim 10^7$ s/eV. These sensitivities are far superior to existing limits from solar-system-bound oscillation experiments. Finally, we demonstrate that using a combination of data from DUNE and HK, one can, in general, distinguish between decaying Dirac neutrinos and decaying Majorana neutrinos.

  • New limits on neutrino non-standard mixings based on prescribed singular values

    by: Flieger, Wojciech
    Singular values are used to construct physically admissible 3-dimensional mixing matrices characterized as contractions. Depending on the number of singular values strictly less than one, the space of the 3-dimensional mixing matrices can be split into four disjoint subsets, which accordingly corresponds to the minimal number of additional, non-standard neutrinos. We show in numerical analysis that taking into account present experimental precision and fits to different neutrino mass splitting schemes, it is not possible to distinguish, on the level of 3-dimensional mixing matrices, between two and three extra neutrino states. It means that in 3+2 and 3+3 neutrino mixing scenarios, using the so-called $\alpha$ parametrization, ranges of non-standard mixings are the same. However, on the level of a complete unitary 3+1 neutrino mixing matrix, using the dilation procedure and the Cosine-Sine decomposition, we were able to shrink bounds for the "light-heavy" mixing matrix elements. For instance, in the so-called seesaw mass scheme, a new upper limit on $|U_{e4}|$ is about two times stringent than before and equals 0.021. For all considered mass schemes the lowest bounds are also obtained for all mixings, i.e. $|U_{e4}| , |U_{\mu 4}| , |U_{\tau 4}|.$

  • Leptonic Scalars at the LHC
    PITT-PACC 1909

    by: de Gouvea, Andre
    We explore the neutrino non-standard interaction with leptonic scalars $\phi$ which are gauge-singlets and carry two units of lepton-number-charge. These leptonic scalars are forbidden from interacting with the Standard Model (SM) fermions at the renormalizable level and, if one allows for higher-dimensional operators, couple predominantly to SM neutrinos. For masses at or below the electroweak scale, $\phi$ decays exclusively into neutrinos. Its unique production signature at hadron collider experiments like the LHC would be via the vector boson fusion process and lead to same-sign dileptons, two forward jets in opposite hemispheres, and missing transverse energy, i.e., $pp \to \ell_\alpha^\pm \ell_\beta^\pm jj + E_T^{\rm miss}$ ($\alpha,\, \beta = e,\, \mu, \tau$). Exploiting the final states of electrons and muons, we estimate, for the first time, the sensitivity of the LHC to these lepton-number-charged scalars. We show that, the sensitivity of high-energy colliders is largely complementary to that of low-energy and precision measurements of the decays of charged leptons, charged mesons, $W$ and $Z$ bosons, neutrino beam experiments like MINOS, searches for light dark matter in NA64, and searches for neutrino self-interactions at IceCube and in cosmological observations. For $\phi$ mass larger than a few GeV, our projected LHC sensitivity would surpass all existing bounds.

  • A model for neutrino-nucleus interactions in the GeV region

    by: Barbaro, Maria B.
    We review the recent progress in modelling neutrino-nucleus scattering, in a framework based on scaling which describes simultaneously the nuclear response to electromagnetic and weak probes. The study is relevant for the analysis of neutrino oscillation data and the design of the next generation experiments Hyper-Kamiokande and DUNE.

  • Multicomponent dark matter in extended $U(1)_{B-L}$: neutrino mass and high scale validity

    by: Bhattacharya, Subhaditya
    Standard Model with right handed neutrinos charged under additional $U(1)_{B-L}$ gauge symmetry offer solutions to both dark matter (DM) problem and neutrino mass generation, although constrained severely from relic density, direct search and Higgs vacuum stability. We therefore investigate a multicomponent DM scenario augmented by an extra inert scalar doublet, that is neutral under $U(1)_{B-L}$, which aids to enlarge parameter space allowed by DM constraints and Higgs vacuum stability. The lightest right-handed neutrino and the $CP$-even inert scalar are taken as the dark matter candidates and constitute a two component dark matter framework as they are rendered stable by an unbroken $\mathbb{Z}_2 \times \mathbb{Z}_2^\prime$ symmetry. DM-DM conversion processes turn out crucial to render requisite relic abundance in mass regions of the RH neutrino that do not appear in the stand-alone $U(1)_{B-L}$ scenario. In addition, the one-loop renormalisation group (RG) equations in this model demonstrate that the electroweak (EW) vacuum can be stabilised till $\sim 10^{9}$ GeV in a parameter region compatible with the observed relic, the direct detection bound and other relevant constraints.

  • A More Complete Phenomenology of Tau Lepton Induced Air Showers
    PoS ICRC2019 (2019) 862

    by: Cummings, Austin
    Many proposed and upcoming experiments seek to observe signals from upward going air showers initiated by tau leptons resulting from neutrino interactions inside the Earth. To save calculation time, event estimations for these observation methods are usually performed while making several assumptions about the showers themselves, which simplifies their rich phenomenology and may or may not lead to inaccuracies in results. Here, we present results of extensive CORSIKA simulations of upward going tau initiated showers in the energy range 1 PeV to 10 EeV. Specifically, we monitor the Cherenkov emission, the charged particle distributions, and the timing of the showers for different geometric configurations. We analyze the impact of the decay length and different decay modes of the tau on particle distributions and compare to primaries usually utilized to simulate a tau shower, such as gammas, electrons, and protons. We also check the accuracy of many of the usual assumptions of these showers and analyze the often ignored muon channel of the tau decay.

  • Top quark as a probe of heavy Majorana neutrino at the LHC and future collider

    by: Liu, Ning
    Right-handed (RH) Majorana neutrinos play a crucial role in understanding the origin of neutrino mass, the nature of dark matter and the mechanism of matter-antimatter asymmetry. In this work, we investigate the observability of heavy RH Majorana neutrino through the top quark neutrinoless double beta decay process $t \to b \ell^+ \ell^+ j j^{\prime}$ ($\ell=e, \mu$) at hadron colliders. By performing detector level simulation, we demonstrate that the heavy neutrinos with the mixing parameters $|V_{eN,\mu N}|^2 \gtrsim 5\times 10^{-6}$ in the mass range of 15 GeV $< m_N <$ 80 GeV can be excluded at $2\sigma$ level at 13 TeV LHC with the luminosity of 36 fb$^{-1}$, which is stronger than other existing collider bounds. The future HL-LHC will be able to further probe the mixings $|V_{eN,\mu N}|^2$ to about $1.4\times 10^{-6}$.

  • Covert symmetries in the neutrino mass matrix

    by: Bjoörkeroth, Fredrik
    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.

  • Physics Potential of ESS$\nu$SB in the presence of a Light Sterile Neutrino

    by: Agarwalla, Sanjib Kumar
    ESS$\nu$SB is a proposed neutrino super-beam project at the ESS facility. It works at the second oscillation maximum and provides high sensitivity towards CP-violation (CPV). We study the performance of this setup in the presence of a light eV-scale sterile neutrino considering 540 km baseline with 2 years (8 years) of $\nu$ ($\bar\nu$) run-plan. We explore in detail its capability in resolving CPV generated by the standard CP phase $\delta_{13}$, the new CP phase $\delta_{14}$, and the octant of $\theta_{23}$. We find that the sensitivity to CPV induced by $\delta_{13}$ deteriorates noticeably when going from $3\nu$ to 4$\nu$ case. The two phases $\delta_{13}$ and $\delta_{14}$ can be reconstructed with a 1$\sigma$ uncertainty of $\sim15^0$ and $ \sim35^0$ respectively. Concerning the octant of $\theta_{23}$, we find poor sensitivity in both $3\nu$ and $4\nu$ schemes. Our results clearly depict that a setup like ESS$\nu$SB working at the second oscillation maximum performs quite well to explore CPV in 3$\nu$ scheme, but it is not optimal for studying CP properties in 3+1 scheme.

  • Gamma-ray signals from multicomponent scalar dark matter decays
    TUM-HEP 1224/19

    by: Ghosh, Avirup
    Within a multicomponent dark matter scenario, novel gamma-ray signals may arise from the decay of the heavier dark matter component into the lighter. For a scalar dark sector of this kind, the decay $\phi_2\rightarrow\phi_1 \gamma$ is forbidden by the conservation of angular momentum, but the decay $\phi_2 \rightarrow \phi_1 \gamma\gamma$ can have a sizable or even dominant branching ratio. In this paper we present a detailed study of this decay channel. We determine the width and photon energy spectrum generated in the decay, employing an effective theory approach, and in UV complete models where the scalar dark matter components interact with heavy or light fermions. We also calculate limits on the inverse width from current data of the isotropic diffuse photon flux, both for a hierarchical and a degenerate dark matter spectrum. Finally, we briefly comment on the prospects of observing the diphoton signal from sneutrino decay in the minimal supersymmetric standard model extended with right-handed neutrino superfields ($\tilde{\nu}$MSSM).

  • Study of Nonstandard Interactions in Rare Decays of Hyprons with Missing Energy

    by: Mahmood, Shakeel
    We study rare decays of hyperons involving di-neutrinos in the final state in the standard model and compare them with other models. It is claimed that the branching ratio calculated in this article are 2 times the values of 331 model and exceptionally large than the previously calculated values. We explore the nonstandard neutrino interactions (NSI) and constrain NSIs free parameter with these decays. We obtain stringent bounds on of O(0.01). We show that branching ratios (Br) could be in the range of BES III if constraints are O(0.3).

  • Neutrino Oscillations in the Vacuum

    by: Ciuffoli, Emilio
    The initial configuration of a neutrino experiment consists of wave packets, created by the experimenter. Unmeasured final states are essentially delocalized, but it is conventional to nonetheless treat them as localized wave packets as they are in a sense measured by the environment. In this note we consider an experiment in the vacuum, and so there is no environment and the unmeasured final states are not localized. We introduce a simplified but consistent model of neutrino interactions and numerically evolve the system over a finite time using the Hamiltonian to obtain the oscillation probability. All particles involved in neutrino production or detection, localized or not, are treated and evolved consistently in quantum field theory, keeping all entanglements.

  • Non-standard interactions versus planet-scale neutrino oscillations

    by: Feng, Wei-Jie
    The low-energy threshold and the large detector size of Precision IceCube Next Generation Upgrade (PINGU) can make the study on neutrino oscillations with a planet-scale baseline possible. In this task, we consider the configuration that neutrinos are produced at CERN and detected in the PINGU detector, as a benchmark. We discuss its sensitivity of measuring the size of non-standard interactions (NSIs) in matter, which can be described by the parameter $\epsilon_{\alpha\beta}$ ($\alpha$ and $\beta$ are flavors of neutrinos). We find that the CERN-PINGU configuration improves $\tilde{\epsilon}_{\mu\mu}\equiv\epsilon_{\mu\mu}-\epsilon_{\tau\tau}$ and $\epsilon_{\mu\tau}$ significantly compared to the next-generation accelerator neutrino experiments. Most of degeneracy problems in the precision measurements can be resolved, except the one for $\tilde{\epsilon}_{\mu\mu}\sim-0.35$. Finally, we point out that this configuration can also be used to detect the CP violation brought by NSIs.

  • Cosmological Dependence of Non-resonantly Produced Sterile Neutrinos

    by: Gelmini, Graciela B.
    We discuss how a laboratory detection of a sterile neutrino not only would constitute a fundamental discovery of a new particle, but could also provide an indication of the evolution of the Universe before Big-Bang Nucleosynthesis (BBN), a fundamental discovery in cosmology. These "visible" sterile neutrinos could be detected in experiments such as KATRIN/TRISTAN and HUNTER in the keV mass range and PTOLEMY, KATRIN and reactor neutrino experiments in the eV mass range. Standard assumptions are usually made to compute the relic abundance and momentum distribution of particles produced before the temperature of the Universe was 5 MeV, an epoch from which there are no observed remnants thus far. However, non-standard pre-BBN cosmologies based on other assumptions that are equally in agreement with all existing data can arise in some theoretical models. We revisit the production of 0.01 eV to 1 MeV sterile neutrinos via non-resonant active-sterile flavor oscillations in several pre-BBN cosmologies. We give general equations for models in which the expansion of the Universe is parametrized by its amplitude and temperature power and where entropy is conserved, which include kination and scalar tensor models as special cases.

  • Long-distance Contributions to Neutrinoless Double Beta Decay $\pi^- \to\pi^+ e e$

    by: Tuo, Xin-Yu (Peking U.) et al.

    Neutrinoless double beta decay, if detected, would prove that neutrinos are Majorana fermions and provide the direct evidence for lepton number violation. If such decay would exist in nature, then $\pi^-\pi^-\to ee$ and $\pi^-\to\pi^+ ee$ (or equivalently $\pi^-e^+\to\pi^+ e^-$) are the two simplest processes accessible via first-principle lattice QCD calculations. In this work, we calculate the long-distance contributions to the $\pi^-\to\pi^+ee$ transition amplitude using four ensembles at the physical pion mass with various volumes and lattice spacings. We adopt the infinite-volume reconstruction method to control the finite-volume effects arising from the (almost) massless neutrino. Providing the lattice QCD inputs for chiral perturbation theory, we obtain the low energy constant $g_\nu^{\pi\pi}(m_\rho)=-10.89(28)_\text{stat}(74)_\text{sys}$, which is close to $g_\nu^{\pi\pi}(m_\rho)=-11.96(31)_\text{stat}$ determined from the crossed-channel $\pi^-\pi^-\to ee$ decay.

  • Probing the Higgs Portal at the Fermilab Short-Baseline Neutrino Experiments

    by: Batell, Brian
    The Fermilab Short-Baseline Neutrino (SBN) experiments, MicroBooNE, ICARUS, and SBND, are expected to have significant sensitivity to light weakly coupled hidden sector particles. Here we study the capability of the SBN experiments to probe dark scalars interacting through the Higgs portal. We investigate production of dark scalars using both the Fermilab Booster 8 GeV and NuMI 120 GeV proton beams, simulating kaons decaying to dark scalars and taking into account the beamline geometry. We also investigate strategies to mitigate backgrounds from beam-related neutrino scattering events. We find that SBND, with its comparatively short ${\cal O}(100\ {\rm m})$ baseline, will have the best sensitivity to scalars produced with Booster, while ICARUS, with its large detector volume, will provide the best limits on off-axis dark scalar production from NuMI. The SBN experiments can provide leading tests of dark scalars with masses in the 50 - 350 MeV range in the near term. Our results motivate dedicated experimental searches for dark scalars and other long-lived hidden sector states at these experiments.

  • Revisiting (s)neutrino dark matter in natural SUSY

    by: Faber, T.
    We study natural supersymmetric scenarios with light right-handed neutrino superfields, and consider the possibility of having either a neutrino or a sneutrino as a dark matter candidate. For the former, we evaluate the possibility of having SUSY corrections on the $\nu_4\to\nu_\ell\gamma$ decay rate, such that the NuStar bounds are relaxed. We find that corrections are too small. For sneutrino dark matter, we consider thermal and non-thermal production, taking into account freeze-out, freeze-in and super-WIMP mechanisms. For the non-thermal case, we find that the $\tilde\nu_R$ can reproduce the observed relic density by adjusting the R-sneutrino mass and Yukawa couplings. For the thermal case, we find the need to extend the model in order to enhance sneutrino annihilations, which we exemplify in a model with an extended gauge symmetry.

  • A $U(1)_{X}$ extension to the SM with three families and Peccei Quinn symmetry

    by: Garnica, Y.A.
    We propose a non-universal $U(1)_{X}$ extension to the Standard Model with three families and an additional global anomala Peccei-Quinn (PQ) symmetry. The breaking of the former allows us to give masses to the exotic fermionic sector and the later generates the necessary zeros in the mass matrices to explain the fermionic mass hierarchy. In addition, the large energy scale associated with the spontaneously breaking (SSB) of the PQ symmetry provides a solution to the strong CP-problem and an axion that could be a possible dark matter candidate. Also, the SSB allows to generate right-handed neutrino masses, so the active neutrinos acquire $eV$-mass values due to the see-saw mechanism implementation.

  • Scalar triplet leptogenesis in the presence of right-handed neutrinos with $S_3$ symmetry

    by: Mishra, Subhasmita (Indian Inst. Tech., Hyderabad) et al.

    Leptogenesis appears to be a viable alternative to account for the baryon asymmetry of the universe through baryogenesis. In this context, we consider a scenario in which the standard model is extended with $S_3$ and $Z_2$ symmetry in addition to the two scalar triplets, two scalar doublets and three right handed neutrinos. Presence of scalar triplets and right-handed neutrinos in the scenarios of both type-I and type-II seesaw framework provide a different leptogenesis option and can help us to understand the matter-antimatter asymmetry with simple $S_3$ symmetry. We discuss the neutrino phenomenology and leptogenesis in both high ($O(10^{10})$ GeV) and low energy scale ($O$(2)TeV) by constraining the Yukawa couplings. Moreover, we also consider the constraints on model parameters from neutrino oscillation data and leptogenesis to explain the rare lepton flavor violating decay and muon g-2 anomaly.

  • Interference effects in semileptonic decays from heavy Majorana neutrinos

    by: Marcano, X.
    Several beyond the Standard Model scenarios introduce new heavy neutrinos, whose Dirac or Majorana nature could be tested by comparing the rates of lepton number violating and lepton number conserving processes: a Dirac fermion induces only the latter, while a Majorana one predicts the same rate for both of them. Nevertheless, in the presence of more than one Majorana fermion, this picture may change drastically due to interference effects. We focus on lepton number violating and lepton flavour violating semileptonic meson decays induced by two heavy Majorana fermions, exploring the necessary conditions to have sizeable interference effects and discussing their implications for current experimental constraints and possible future observations. In particular, we show how the $CP$ violating phases may lead to an enhancement of the lepton number violating modes and suppression of the lepton number conserving ones, and vice-versa.

  • Constraints on Sterile Neutrinos in the MeV to GeV Mass Range
    TRIUMF-UBC-Stony Brook preprint (YITP-SB-2019-9)

    by: Bryman, D.A. (British Columbia U.) et al.

    A detailed discussion is given of the analysis of recent data to obtain improved upper bounds on the couplings $|U_{e4}|^2$ and $|U_{\mu 4}|^2$ for a mainly sterile neutrino mass eigenstate $\nu_4$. Using the excellent agreement among ${\cal F}t$ values for superallowed nuclear beta decay, an improved upper limit is derived for emission of a $\nu_4$. The agreement of the ratios of branching ratios $R^{(\pi)}_{e/\mu}=BR(\pi^+ \to e^+ \nu_e)/BR(\pi^+ \to \mu^+ \nu_\mu)$, $R^{(K)}_{e/\mu}$, $R^{(D_s)}_{e/\tau}$, $R^{(D_s)}_{\mu/\tau}$, and $R^{(D)}_{e/\tau}$, and the branching ratios $BR(B^+\rightarrow e^+\nu_e)$ and $BR(B^+\rightarrow \mu^+\nu_\mu)$ decays with predictions of the Standard Model, is utilized to derive new constraints on $\nu_4$ emission covering the $\nu_4$ mass range from MeV to GeV. We also discuss constraints from peak search experiments probing for emission of a $\nu_4$ via lepton mixing, as well as constraints from pion beta decay, CKM unitarity, $\mu$ decay, leptonic $\tau$ decay, and other experimental inputs.

  • Matter effects and coherent effect of neutrinos produced from -ray bursts
    Chin.Phys. C43 (2019) 105102

    by: Liu, Kuan (Chongqing CTBU) et al.

    Neutrinos produced from -ray bursts (GRBs) carry significant physical information. The electron density in the GRBs outflow is very large. In this study, we calculate the matter effect on neutrinos when they propagate through such a dense region. The average survival probability and the flavor ratio of neutrinos are determined. The ratio of resonant neutrino energy from different spherical shells provides the information of power index N for the power-law distribution of electrons in the hot fireball model. Electron density in the magnetic jet model is sufficiently lower than in the hot fireball model. The matter effect on neutrinos can be used to distinguish these two models. The coherent effect of strongly lensed PeV neutrinos is also discussed. The average survival probability of strongly-lensed electron neutrinos in the normal and inverted hierarchical cases are presented. The results show that this coherent effect can be used to determine the hierarchical mass of neutrinos.

  • Neutrino decoherence in a fermion and scalar background

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

    We consider the decoherence effects in the propagation of neutrinos in a background composed of a scalar particle and a fermion due to the non-forward neutrino scattering processes. Using a simple model for the coupling of the form $\bar f_R\nu_L\phi$ we calculate the contribution to the imaginary part of the neutrino self-energy arising from the non-forward neutrino scattering processes in such backgrounds, from which the damping terms are determined. In the case we are considering, in which the initial neutrino state is depleted but does not actually disappear (the initial neutrino transitions into a neutrino of a different flavor but does not decay into a $f\phi$ pair, for example), we associate the damping terms with decoherence effects. For this purpose we give a precise prescription to identify the decoherence terms, as used in the context of the master or Linblad equation, in terms of the damping terms we have obtained from the calculation of the imaginary part of the neutrino self-energy from the non-forward neutrino scattering processes. The results can be directly useful in the context of Dark Matter-neutrino interaction models in which the scalar and/or fermion constitute the dark-matter, and can also serve to guide the generalizations to other models and/or situations in which the decoherence effects in the propagation of neutrinos originate from the non-forward scattering processes may be important. As a guide to estimating such decoherence effects, the contributions to the absorptive part of the self-energy and the corresponding damping terms are computed explicitly in the context of the model we consider, for several limiting cases of the momentum distribution functions of the background particles.

  • Formal Developments for Lorentz-Violating Dirac Fermions and Neutrinos
    Symmetry 11 (2019) 1197

    by: Andrade de Simões dos Reis, João Alfíeres (UFMA, Bacanga) et al.

    The current paper is a technical work that is focused on Lorentz violation for Dirac fermions as well as neutrinos, described within the nonminimal Standard-Model Extension. We intend to derive two theoretical results. The first is the full propagator of the single-fermion Dirac theory modified by Lorentz violation. The second is the dispersion equation for a theory of $N$ neutrino flavors that enables the description of both Dirac and Majorana neutrinos. As the matrix structure of the neutrino field operator is very involved for generic $N$, we will use sophisticated methods of linear algebra to achieve our objectives. Our main finding is that the neutrino dispersion equation has the same structure in terms of Lorentz-violating operators as that of a modified single-fermion Dirac theory. The results will be valuable for phenomenological studies of Lorentz-violating Dirac fermions and neutrinos.

  • Comment on the article by D. Borah and B. Karmakar "Linear seesaw for Dirac neutrinos with A4 flavour symmetry", Phys. Lett. B789 (2019) 59-70, arXiv: 1806.10685
    Phys.Lett. B798 (2019) 134979

    by: Vien, V.V. (Vietnam Natl. U., Ho Chi Minh) et al.

    D. Borah and B. Karmakar in Phys. Lett. B789 (2019) have proposed an A4 flavoured linear seesaw model to realise light Dirac neutrinos. In this comment article, we show that some neutrino Yukawa interactions were missed in the model, thus implying that a different formula would be needed to determine the effective neutrino mass matrix, with significantly different results. Our result shows that, unlike stated in Phys. Lett. B789 (2019), that the inverted neutrino mass spectrum is not ruled out.

  • Novel matter effects on neutrino oscillations observables

    by: Zettel, Adam (Central Michigan U.) et al.

    In a recent article (arxiv:1803.06332) we noticed that the electron density in condensed matter exhibits large spikes close to the atomic nuclei. We showed that these spikes in the electron densities, 3-4 orders of magnitude larger than those inside the Sun's core, have no effect on the neutrino emission and absorption probabilities or on the neutrinoless double beta decay probability. However, it was not clear if the effect of these spikes is equivalent to that of an average constant electron density in matter. We investigated these effects by a direct integration of the coupled Dirac equations describing the propagation of flavor neutrinos into, through, and out of the matter. We found little evidence that these spikes affect the standard oscillations probabilities, but found a new fast and efficient algorithm of calculating these probabilities for neutrinos propagating through varying electron densities.

  • Remarks on the Unruh effect with mixed neutrinos
    J.Phys.Conf.Ser. 1275 (2019) 012063

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

    We discuss some recent results on the inverse β-decay of an accelerated proton in the presence of neutrino mixing. By comparing different approaches, we conclude that a consistent treatment preserving general covariance should be based on flavor neutrino states. We also comment on the issue of thermality of the Unruh effect for mixed neutrinos.

  • Three flavor neutrino conversions in supernovae: Slow $\&$ Fast instabilities

    by: Chakraborty, Madhurima (Indian Inst. Tech., Guwahati) et al.

    Self induced neutrino flavor conversions in the dense regions of stellar core collapse are almost exclusively studied in the standard two flavor scenario. Linear stability analysis has been successfully used to understand these flavor conversions. This is the first linearized study of $\textit{three flavor}$ fast instabilities. The `fast' conversions are fascinating distinctions of the dense neutrino systems. In the fast modes the collective oscillation dynamics are independent of the neutrino mass, growing at the scale of the large neutrino-neutrino interaction strength ($10^5$ km$^{-1}$) of the dense core. This is extremely fast, in comparison to the usual `slow' collective modes driven by much smaller vacuum oscillation frequencies ($10^0$ km$^{-1}$). The three flavor analysis shows distinctive characteristics for both the slow and the fast conversions. The slow oscillation results are in qualitative agreement with the existing nonlinear three flavor studies. For the fast modes, addition of the third flavor opens up possibilities of influencing the growth rates of flavor instabilities when compared to a two flavor scenario.

  • Observing EeV neutrinos through the Earth: GZK and the anomalous ANITA events

    by: Safa, Ibrahim (Wisconsin U., Madison) et al.

    Tau neutrinos are unique cosmic messengers, especially at extreme energies. When they undergo a charged-current interaction, the short lifetime of the produced tau gives rise to secondary tau neutrinos that carry a significant fraction of the primary neutrino energy. This effect, known as tau neutrino regeneration, has not been applied to its full potential in current generation neutrino experiments. In this work, we present an updated calculation of tau neutrino regeneration, and explore its implications for two scenarios: the recent anomalous ANITA events and the cosmogenic neutrino flux. For the former, we investigate the idea of localized emission and find that the maximum secondary neutrino flux allowed by IceCube measurements implies a primary flux that is incompatible with the ANITA observation, regardless of the assumed source energy spectrum. For the latter, we study the prospect of detecting the cosmogenic neutrino flux of regenerated PeV neutrinos with current and next generation neutrino detectors.

  • Neutrino Oscillations in Dark Matter

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

    We study neutrino oscillations in a medium of dark matter which generalizes the standard matter effect. A general formula is derived to describe the effect of various mediums and their mediators to neutrinos. Neutrinos and anti-neutrinos receive opposite contributions from asymmetric distribution of (dark) matter and anti-matter, and thus it could appear in precision measurement of neutrino or anti-neutrino oscillations. Furthermore, the standard neutrino oscillation can occur from the symmetric dark matter effect even for massless neutrinos.

  • Probing Doubly and Singly Charged Higgs at $pp$ Collider HE-LHC

    by: Padhan, Rojalin (Bhubaneswar, Inst. Phys.) et al.

    We analyse the signal sensitivity of multi-lepton final states at collider that can arise from doubly and singly charged Higgs decay in a type-II seesaw framework. We assume triplet vev to be very small and degenerate masses for both the charged Higgs states. The leptonic branching ratio of doubly and singly charged Higgs states have a large dependency on the neutrino oscillation parameters, lightest neutrino mass scale, as well as neutrino mass hierarchy. We explore this as well as the relation between the leptonic branching ratios of the singly and doubly charged Higgs states in detail. We evaluate the effect of these uncertainties on the production cross-section. Finally, we present a detailed analysis of multi-lepton final states for a future hadron collider HE-LHC, that can operate with center of mass energy $\sqrt{s}=27$ TeV.

  • Gravitational footprints of massive neutrinos and lepton number breaking

    by: Addazi, Andrea (Fudan U.) et al.

    We investigate the production of primordial Gravitational Waves (GWs) arising from First Order Phase Transitions (FOPTs) associated to neutrino mass generation in the context of type-I seesaw schemes. We examine both "high-scale" as well as "low-scale" variants, with either explicit or spontaneously broken lepton number symmetry. In the latter case, a pseudo-Goldstone boson, dubbed majoron, may provide a candidate for warm or cold cosmological dark matter. We find that schemes without majoron lead to either no FOPTs or too weak FOPTs, precluding the detectability of GWs in present or near future experiments. Nevertheless, we found that, in the presence of majorons, one can have strong FOPTs and non-trivial primordial GW spectra which can fall well within the frequency and amplitude sensitivity of upcoming experiments, including LISA, BBO and u-DECIGO. We further analyze the associated types of FOPTs and show that in certain cases, the resulting GW spectra entail, as characteristic features, double or multiple peaks, which can be resolved in forthcoming experiments. We also found that the majoron variant of the low-scale seesaw mechanism implies a different GW spectrum than the one expected in the high-scale majoron seesaw. This feature will be testable in future experiments. Our analysis shows that GWs can provide a new and complementary portal to test the neutrino mass sector.

  • Quantifying multinucleon effect in the Ar-target using High Pressure gas TPC DUNE Near Detector

    by: Singh, Jaydip (Lucknow U.) et al.

    Different neutrino oscillation experiments use nuclear targets for the study of exotic physics. Nuclear effects are introduced in the experimental environment by the use of these targets and need to be quantified as they add to the systematic errors. In low energy region(around 1 GeV) multi-nucleon events are present along with QE and Delta interactions. Therefore if these multinucleon events are not incorporated in the data set properly, we end up with an inaccurate reconstruction of neutrino energy. In our work, we have illustrated the importance of incorporation of multinucleon events for the reduction of systematic errors in physics predictions for DUNE. To achieve this we have presented the event distribution ratio of Ar/C, Ar/Ar and C/C as a function of squared four momentum transfer by employing different nuclear models. This analysis recommends the addition of 2p2h or multinucleon events in the event sample and promotes model with RPA effect for the analysis of the event sample to overcome or reduce the systematic uncertainties

  • Fermion Mass and Mixing in a Low-Scale Seesaw Model based on the $S_4$ Flavor Symmetry

    by: Vien, V.V. (Vietnam Natl. U., Ho Chi Minh) et al.

    We construct a low-scale seesaw model to generate the masses of active neutrinos based on $S_4$ flavor symmetry supplemented by the $Z_2 \times Z_3 \times Z_4 \times Z_{14}\times U(1)_L$ group, capable of reproducing the low energy Standard model (SM) fermion flavor data. The masses of the SM fermions and the fermionic mixings parameters are generated from a Froggatt-Nielsen mechanism after the spontaneous breaking of the $S_4\times Z_2 \times Z_3 \times Z_4 \times Z_{14}\times U(1)_L$ group. The obtained values for the physical observables of the quark and lepton sectors are in good agreement with the most recent experimental data. The leptonic Dirac CP violating phase $\de _{CP}$ is predicted to be $259.579^\circ$ and the predictions for the absolute neutrino masses in the model can also saturate the recent constraints.

  • Dirac neutrino mass generation from Majorana messenger

    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 vector-like 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 $\Delta N_{\text{eff}}$ reported by PLANCK points to large ratios $M_{Z'}/g'\gtrsim 40\ \text{TeV}$ 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.

  • Explaining the MiniBooNE excess by a decaying sterile neutrino with mass in the 250 MeV range

    by: Fischer, Oliver (KIT, Karlsruhe, IKP) et al.

    The MiniBooNE collaboration has reported an excess of $460.5\pm 95.8$ electron-like events ($4.8\sigma$). We propose an explanation of these events in terms of a sterile neutrino decaying into a photon and a light neutrino. The sterile neutrino has a mass around 250 MeV and it is produced from kaon decays in the proton beam target via mixing with the muon or the electron in the range $10^{-11} \lesssim |U_{\ell 4}|^2 \lesssim 10^{-7}$ ($\ell = e,\mu$). The model can be tested by considering the time distribution of the events in MiniBooNE and by looking for single-photon events in running or upcoming neutrino experiments, in particular by the suite of liquid argon detectors in the short-baseline neutrino program at Fermilab.

  • Solar Neutrino Limits on Decoherence

    by: de Holanda, Pedro Cunha (Unlisted)

    The solar neutrino flux arrives at Earth as an incoherent admixture of mass eigenstates, and then solar neutrino detection constitute a blind probe to the oscillation pattern of the neutrino flavour conversion. Consequently, it is also impossible to probe, in a model independent approach, any new physics that leads to an enhancement of decoherence during the neutrino evolution, an effect that is present for instance in Open Quantum System formalism. However, such mechanism can also induce changes between mass eigenstates if an energy interchange between the neutrino subsystem and the reservoir is not explicitly forbidden. In this work the conversion probabilities between mass eigenstates in an Open Quantum System are calculated, and limits are stablished for these kind of transitions. We present our results in a pedagogical way, pointing out how far the analysis can go without any assumption on the neutrino conversion physics inside the Sun, before performing the full calculations. We obtain as limits for the decoherence parameters the values of $ \Gamma_3< 6.5\times 10^{-19}$ eV and $\Gamma_8< 7.1\times 10^{-19}$ eV at 3$\sigma$.

  • Flavor structures of charged fermions and massive neutrinos

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

    Most of the free parameters in the Standard Model (SM) --- a quantum field theory which has successfully elucidated the behaviors of strong, weak and electromagnetic interactions of all the known fundamental particles, come from the lepton and quark flavors. The discovery of neutrino oscillations has proved that the SM is incomplete, at least in its lepton sector; and thus the door of opportunity is opened to exploring new physics beyond the SM and solving a number of flavor puzzles. In this review article we give an overview of important progress made in understanding the mass spectra, flavor mixing patterns, CP-violating effects and underlying flavor structures of charged leptons, neutrinos and quarks in the past twenty years. After introducing the standard pictures of fermion mass generation, flavor mixing and CP violation in the SM extended with the presence of massive Dirac or Majorana neutrinos, we briefly summarize current experimental knowledge about the flavor parameters of quarks and leptons. Various ways of describing flavor mixing and CP violation are discussed, the renormalization-group evolution of flavor parameters is illuminated, and the matter effects on neutrino oscillations are interpreted. Taking account of possible extra neutrino species, we propose a standard parametrization of the $6\times 6$ flavor mixing matrix and comment on the phenomenological aspects of heavy, keV-scale and light sterile neutrinos. We pay particular attention to those novel and essentially model-independent ideas or approaches regarding how to determine the Yukawa textures of Dirac fermions and the effective mass matrix of Majorana neutrinos, including simple discrete and continuous flavor symmetries. An outlook to the future development in unravelling the mysteries of flavor structures is also given.

  • Implications of the Dark LMA solution and Fourth Sterile Neutrino for Neutrino-less Double Beta Decay

    by: Deepthi, K.N. (Unlisted, IN) et al.

    We analyze the effect of the Dark-large mixing angle (DLMA) solution on the effective Majorana mass ($m_{\beta\beta}$) governing neutrino-less double beta decay ($0\nu\beta\beta$) in the presence of a sterile neutrino. We consider the 3+1 picture, comprising of one additional sterile neutrino. We have checked that the MSW resonance in the sun can take place in the DLMA parameter space in this scenario. Next we investigate how the values of the solar mixing angle $\theta_{12}$ corresponding to the DLMA region alter the predictions of $m_{\beta\beta}$ including a sterile neutrino in the analysis. We also compare our results with three generation cases for both standard large mixing angle (LMA) and DLMA. Additionally, we evaluate the discovery sensitivity of the future ${}^{136}Xe$ experiments in this context.

  • Reevaluating Reactor Antineutrino Anomalies with Updated Flux Predictions

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

    Hints for the existence of a sterile neutrino at nuclear reactors are reexamined using two updated predictions for the fluxes of antineutrinos produced in fissions. These new predictions diverge in their preference for the rate deficit anomaly, relative to previous analyses, but the anomaly in the ratios of measured antineutrino spectra persists. We comment on upcoming experiments and their ability to probe the preferred region of the sterile-neutrino parameter space in the electron neutrino disappearance channel.

  • Low scale seesaw models for low scale $U(1)_{L_\mu-L_\tau}$ symmetry

    by: Araki, Takeshi (Tokyo U.) et al.

    We propose models for neutrino masses and mixing in the framework of low scale $U(1)_{L_\mu-L_\tau}$ gauge extension of the standard model. The models are designed to spontaneously break $U(1)_{L_\mu-L_\tau}$ so that the $U(1)_{L_\mu-L_\tau}$ gauge boson acquires an MeV scale mass, which is required to solve the long-standing problem of muon anomalous magnetic moment. Tiny neutrino masses are obtained by simultaneously invoking the linear and the inverse seesaw mechanism, and we succeed in realizing two types of one-zero textures in the active neutrino mass matrix. Both of the obtained textures favor inverted neutrino mass ordering and are testable in next generation experiments of neutrinoless double beta decay. We also show that some of extra scalar bosons can have MeV scale masses and would have significant impacts on observations of high energy cosmic neutrinos.

  • Comment on "An improved upper limit on the neutrino mass from a direct kinematic method by KATRIN"

    by: Chodos, Alan (Texas U., Arlington)

    We note that the central value of the KATRIN measurement has negative mass squared, and wonder why the statistical analysis excludes such values a priori.

  • Efficient Cosmological Analysis of the SDSS/BOSS data from the Effective Field Theory of Large-Scale Structure

    by: Colas, Thomas (Stanford U., ITP) et al.

    The precision of the cosmological data allows us to accurately approximate the predictions for cosmological observables by Taylor expanding up to a low order the dependence on the cosmological parameters around a reference cosmology. By applying this observation to the redshift-space one-loop galaxy power spectrum of the Effective Field Theory of Large-Scale Structure, we analyze the BOSS DR12 data by scanning over all the parameters of $\Lambda$CDM cosmology with massive neutrinos. We impose several sets of priors, the widest of which is a Big Bang Nucleosynthesis prior on the current fractional energy density of baryons, $\Omega_b h^2$, and a 20\% flat prior on $n_s$. In this case we measure the primordial amplitude of the power spectrum, $A_s$, the abundance of matter, $\Omega_m$, and the Hubble parameter, $H_0$, to about $15\%$, $5.0\%$ and $1.9\%$ respectively, obtaining $\ln ( 10^{10} A_s) = 2.87\pm 0.15$, $\Omega_m=0.316\pm 0.016$, $H_0=69.0\pm 1.3$ km/(s Mpc) at 68\% confidence level. A public code is released with this preprint.

  • Type-I thermal leptogenesis in $Z_3$-symmetric three Higgs doublet model

    by: Chakraborty, Indrani (Indian Inst. Tech., Kanpur) et al.

    Our present work explores the possibility of neutrino mass generation through {\em Type-I see-saw} mechanism and provides an explanation of the baryon asymmetry of the Universe via thermal leptogenesis in the framework of $Z_3$-symmetric three Higgs doublet model (3HDM) augmented with three right-handed neutrinos. Here the thermal leptogenesis is initiated by the out-of-equilibrium decay of the lightest heavy neutrino $N_1$. The constraints arising out of the scalar sector put strong bound on the model parameter $\tan \beta$, which in turn takes part in the computation of the lepton asymmetry $\epsilon$. Lepton asymmetry being converted partially into the baryon asymmetry by electroweak sphelaron processes, will account for the required baryon asymmetry satisfying the current data. We therefore analyse the parameter space consistent with the constraints arising from neutrino oscillation, lepton asymmetry and baryon asymmetry together, last one being the most stringent one.

  • The 2-Neutrino-Exchange Potential with Mixing: A New Arena for Neutrino Mixing and CP-Violation

    by: Le Thien, Q. (Wabash Coll.) et al.

    The 2-neutrino exchange potential (2NEP) is a Standard Model (SM) weak potential due to the exchange of virtual neutrino-antineutrino pairs. Consequently, many aspects of neutrino physics, such as the number of flavors, their masses, fermionic nature (Dirac or Majorana), low-energy neutrino physics and CP-violation, can be examined via the 2NEP. We present a new approach for calculating the 2NEP taking into account the phenomenon of neutrino mixing and CP-violation which arises from the structure of the SM weak interaction Lagrangian. Lastly, we explore implications of our result in various physical contexts.

  • Wolfenstein potentials for neutrinos induced by ultra-light mediators

    by: Smirnov, Alexei Yu (Heidelberg, Max Planck Inst.) et al.

    New physics can emerge at low energy scales, involving very light and very weakly interacting new particles. These particles can mediate interactions between neutrinos and usual matter and contribute to the Wolfenstein potential relevant for neutrino oscillations. We compute the Wolfenstein potential in the presence of ultra-light scalar and vector mediators and study the dependence of the potential on the mediator mass $m_A$, taking the finite size of matter distribution (Earth, Sun, supernovae) into consideration. For ultra-light mediators with $m_{A}^{-1}$ comparable to the size of the medium ($R$), the usual $m_{A}^{-2}$ dependence of the potential is modified. In particular, when $m_{A}^{-1}\gg R$, the potential does not depend on $m_{A}$. Taking into account existing bounds on light mediators, we find that for the scalar case significant effects on neutrino propagation are not possible, while for the vector case large matter effects are allowed for $m_{A} \in [2\times10^{-17}$, $4\times10^{-14}]$ eV and the gauge coupling $g\sim 10^{-25}$.

  • Charged lepton flavour change and Non-Standard neutrino Interactions

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

    Non-Standard 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 $m_W$ that does not induce (charged) Lepton Flavour Violation (LFV) at tree level, and show that LFV is generated at one loop in most cases. The current constraints on charged Lepton Flavour Violation therefore suggest that mu <---> e flavour-changing NSI are unobservable and tau <---> l flavour-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.

  • Doubly Charged Scalar at the High-Luminosity and High-Energy LHC
    Int.J.Mod.Phys. A34 (2019) 1950157

    by: de Melo, Tessio B. (IIP, Brazil) et al.

    Doubly charged scalars are common figures in several beyond the Standard Model studies, especially those related to neutrino masses. In this work, we estimate the High-Luminosity (HL-LHC) and High-Energy LHC (HE-LHC) sensitivity to doubly charged scalars assuming they decay promptly and exclusively into charged leptons. Our study focuses on the fit to the same-sign dilepton mass spectra and it is based on proton-proton collisions at $13$ TeV, $14$ TeV and $27$ TeV with integrated luminosity of $\mathcal{L}=139 fb^{-1}, 3 $ab$^{-1}$ and $15$ab$^{-1}$. We find that HL-LHC may probe doubly charged scalars masses up to $2.3$ TeV, whereas HE-LHC can impressively probe masses up to $3$ TeV, conclusively constituting a complementary and important probe to signs of doubly charged scalars in lepton flavor violation decays and lepton-lepton colliders.

  • Neutrino oscillation analysis of 217 live-days of Daya Bay and 500 live-days of RENO

    by: Acero, Mario A. (U. Atlantico, Barranquilla) et al.

    We present a neutrino oscillation analysis of two particular data sets from the Daya Bay and RENO reactor neutrino experiments aiming to study the increase in precision in the oscillation parameters $\sin^2{2\theta}_{13}$ and the effective mass splitting $\Delta m^2_{ee}$ gained by combining two relatively simple to reproduce analyses available in the literature. For Daya Bay the data from 217 days between December 2011 and July 2012 were used. For RENO we used the data from 500 live days between August 2011 and January 2012. We reproduce reasonably well the results of the individual analyses, both, rate-only and spectral, defining a suitable $\chi^2$ statistic for each case. Finally, we performed a combined spectral analysis and extract tighter constraints on the parameters, with an improved precision between 30-40\% with respect of the individual analyses considered.

  • Search for Dark Matter Annihilation to Neutrinos from the Sun
    ICRC 2019: Review Sign-up ICRC 2019: Review Sign-up 100% 11 PoS-ICRC2019-527 Screen reader support enabled. PoS-ICRC2019-527 3 collaborators have joined the document

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

    Weakly interacting massive particles (WIMPs) can be gravitationally captured by the Sun and trapped in its core. The annihilation of those WIMPs into Standard Model particles produces a spectrum of neutrinos whose energy distribution is related to the dark matter mass. In this work, we present the theoretical framework for relating an observed neutrino flux to the WIMP-nucleon cross section and summarize a previous solar WIMP search carried out by IceCube. We then outline an ongoing updated solar WIMP search, focusing on improvements over the previous search.

  • Entanglement and collective flavor oscillations in a dense neutrino gas
    Phys.Rev. D100 (2019) 083001

    by: Cervia, Michael J. (Wisconsin U., Madison) et al.

    We investigate the importance of going beyond the mean-field approximation in the dynamics of collective neutrino oscillations. To expand our understanding of the coherent neutrino oscillation problem, we apply concepts from many-body physics and quantum information theory. Specifically, we use measures of nontrivial correlations (otherwise known as “entanglement”) between the constituent neutrinos of the many-body system, such as the entanglement entropy and the Bloch vector of the reduced density matrix. The relevance of going beyond the mean field is demonstrated by comparisons between the evolution of the neutrino state in the many-body picture vs the mean-field limit, for different initial conditions.

  • Reduced uncertainty of the axial $\gamma Z$-box correction to the proton's weak charge
    Phys.Rev. D100 (2019) 053007

    by: Erler, Jens (U. Mainz, PRISMA) et al.

    We present the fully up-to-date calculation of the γZ-box correction which needs to be taken into account to determine the weak mixing angle at low energies from parity-violating electron proton scattering. We make use of neutrino and antineutrino inclusive scattering data to predict the parity-violating structure function F3γZ by isospin symmetry. Our new analysis confirms previous results for the axial contribution to the γZ-box graph and reduces the uncertainty by a factor of 2. In addition, we note that the presence of parity-violating photon-hadron interactions induces an additional contribution via F3γγ. Using experimental and theoretical constraints on the nucleon anapole moment we are able to estimate the uncertainty associated with this contribution. We point out that future measurements are expected to significantly reduce this latter uncertainty.

  • Anomalous ANITA air shower events and tau decays
    Phys.Rev. D100 (2019) 063011

    by: Chipman, Shoshana (Chicago U., Astron. Astrophys. Ctr.) et al.

    Two unusual neutrino events in the Antarctic Impulse Transient Antenna (ANITA) appear to have been generated by air showers from a particle emerging from the Earth at angle ∼25°–35° above the horizon. We evaluate the effective aperture for ANITA with a simplified detection model to illustrate the features of the angular dependence of expected events for incident standard model tau neutrinos and for sterile neutrinos that mix with tau neutrinos. We apply our sterile neutrino aperture results to a dark matter scenario with long-lived supermassive dark matter that decay to sterile neutrinolike particles. We find that for upgoing air showers from tau decays, from isotropic fluxes of standard model, sterile neutrinos, or other particles that couple to the tau through suppressed weak interaction cross sections cannot be responsible for the unusual events.

  • Pati-Salam unification with a spontaneous CP violation
    Phys.Rev. D100 (2019) 055019

    by: Suematsu, Daijiro (Kanazawa U., Inst. Theor. Phys.)

    Recent neutrino oscillation experiments suggest that the Pontecorvo-Maki-Nakagawa-Sakata matrix in the lepton sector has a CP violating phase like the Cabibbo-Kobayashi-Maskawa matrix in the quark sector. However, the origins of these phases in both matrices are not clarified by now. Although complex Yukawa couplings could induce these phases, the phases remain as free parameters of the model even in that case. If the CP symmetry is considered to be spontaneously broken, they are expected to be determined by some physics at a much lower energy scale than the Planck scale. We study such a possibility in a framework of Pati-Salam-type unification. We also discuss other phenomenological issues in it.

  • Multi-Messenger Astrophysics
    Nature Rev.Phys. 1 (2019) 585-599

    by: Mészáros, Péter (Penn State U., Astron. Astrophys.) et al.

    Multi-messenger astrophysics, a long-anticipated extension to traditional multiwavelength astronomy, has emerged over the past decade as a distinct discipline providing unique and valuable insights into the properties and processes of the physical Universe. These insights arise from the inherently complementary information carried by photons, gravitational waves, neutrinos and cosmic rays about individual cosmic sources and source populations. This complementarity is the reason why multi-messenger astrophysics is much more than just the sum of the parts. In this Review article, we survey the current status of multi-messenger astrophysics, highlighting some exciting results, and discussing the major follow-up questions they have raised. Key recent achievements include the measurement of the spectrum of ultrahigh-energy cosmic rays out to the highest observable energies, the discovery of the diffuse high-energy neutrino background, the first direct detections of gravitational waves and the use of gravitational waves to characterize merging black holes and neutron stars in strong-field gravity, and the identification of the first joint electromagnetic plus gravitational wave and electromagnetic plus high-energy neutrino multi-messenger sources. We discuss the rationales for the next generation of multi-messenger observatories, and outline a vision of the most likely future directions for this exciting and rapidly growing field.

  • $B$ anomalies in the nonminimal universal extra dimension model
    Phys.Rev. D100 (2019) 075005

    by: Lee, Jong-Phil (Konkuk U.)

    We investigate B anomalies in the framework of the nonminimal universal extra dimension model. Newly measured polarization parameters in B→D(*)τν, Pτ(D(*)), and FL(D*) as well as the ratios R(D(*)) are considered altogether. The Kaluza-Klein modes of the W boson and charged scalar contributes to the new physics effects. We find that the model parameters fit the global data very well with the minimum χ2/d.o.f. near unity, rendering Bc→τν branching ratios to be a few percent. The best-fit values of R(D) and R(D*) are still far from (≳2σ) the standard model predictions.

  • Confronting tridirect CP -symmetry models with neutrino oscillation experiments
    Phys.Rev. D100 (2019) 055022

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

    Tridirect CP symmetry is an economical neutrino model building paradigm, and it allows for the description of neutrino masses, mixing angles, and CP violation phases in terms of four free parameters. The viability of a class of tridirect CP models is examined with a comprehensive simulation of current and future neutrino oscillation experiments. The full parameter space of four independent parameters is carefully scanned, and the problem of parameter degeneracy appears for the constraints from one group of neutrino oscillation experiments. Two benchmark models which are promising from a model building point of view are also examined. Complementary roles from accelerator neutrino experiments (e.g., T2HK and DUNE) and reactor neutrino experiments (e.g., JUNO) are crucial to break the degeneracy and nail down the fundamental neutrino mixing parameters of the underlying theory.

  • Relic neutrino detection through angular correlations in inverse $\beta$-decay
    JCAP 1909 (2019) 031

    by: Akhmedov, Evgeny (Heidelberg, Max Planck Inst.)

    Neutrino capture on beta-decaying nuclei is currently the only known potentially viable method of detection of cosmic background neutrinos. It is based on the idea of separation of the spectra of electrons or positrons produced in captures of relic neutrinos on unstable nuclei from those from the usual β-decay and requires very high energy resolution of the detector, comparable to the neutrino mass. In this paper we suggest an alternative method of discrimination between neutrino capture and β-decay, based on periodic variations of angular correlations in inverse beta decay transitions induced by relic neutrino capture. The time variations are expected to arise due to the peculiar motion of the Sun with respect to the CνB rest frame and the rotation of the Earth about its axis and can be observed in experiments with both polarized and unpolarized nuclear targets. The main advantage of the suggested method is that it does not depend crucially on the energy resolution of detection of the produced β-particles and can be operative even if this resolution exceeds the largest neutrino mass.

  • Neutrino event generators: foundation, status and future
    J.Phys. G46 (2019) 113001

    by: Mosel, Ulrich (Giessen U.)

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

  • Neutrino nature, total and geometric phase
    J.Phys.Conf.Ser. 1275 (2019) 012053

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

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

  • Type I + II Seesaw in a Two Higgs Doublet Model
    Phys.Lett. B797 (2019) 134813

    by: Cogollo, D. (Campina Grande Federal U.) et al.

    Two Higgs Doublet Models (2HDM) are popular extensions of the Standard Model for several reasons, but do not explain neutrino masses. In this work, we investigate how one can incorporate neutrino masses within the framework of the 2HDM-U(1), where U(1) is an abelian gauge symmetry used to nicely address the absence of flavor changing neutral currents in 2HDM. In particular, we explore realizations of the type I and type II seesaw since they are mechanisms that we dote on for being able to generate elegantly small active neutrino masses. We show that one can build several models featuring type I, type II and type I+II seesaw mechanism with different phenomenological implications.

  • Improved Constraints on Sterile Neutrinos in the MeV to GeV Mass Range
    UBC-TRIUMF-Stony Brook preprint (YITP-SB-2019-2)
    Phys.Rev. D100 (2019) 053006

    by: Bryman, D.A. (British Columbia U.) et al.

    Improved upper bounds are presented on the coupling $|U_{e4}|^2$ of an electron to a sterile neutrino $\nu_4$ from analyses of data on nuclear and particle decays, including superallowed nuclear beta decays, the ratios $R^{(\pi)}_{e/\mu}=BR(\pi^+ \to e^+ \nu_e)/BR(\pi^+ \to \mu^+ \nu_\mu)$, $R^{(K)}_{e/\mu}$, $R^{(D_s)}_{e/\tau}$, and $B^+_{e 2}$ decay, covering the mass range from MeV to GeV.

  • Minimal two-component scalar doublet dark matter with radiative neutrino mass
    Phys.Rev. D100 (2019) 055027

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

    We propose a minimal extension of the Standard Model to accommodate two-component dark matter (DM) and light neutrino mass. The symmetry of the Standard Model is enhanced by an unbroken Z2×Z2′ such that being odd under each Z2, there exists one right-handed neutrino and one inert scalar doublet. Therefore, each of the Z2 sectors contribute to (i) light neutrino masses radiatively similar to the scotogenic models while (ii) the two neutral CP even scalars present in two additional inert doublets play the role of dark matters. Focusing on the intermediate range of inert scalar doublet DM scenario: MW≤MDM≲500  GeV, where one scalar doublet DM cannot satisfy correct relic, we show that this entire range becomes allowed within this two-component scalar doublet DM, thanks to the interconversion between the two DM candidates in the presence of neutrino Yukawa couplings with dark sector.

  • A modular $A_4$ symmetric model of dark matter and neutrino
    APCTP Pre2019 - 007
    Phys.Lett. B797 (2019) 134799

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

    We propose a model based on modular A4 symmetry containing a dark matter candidate, realizing radiatively induced neutrino mass at one-loop level. One finds that stability of dark matter candidate can be assured by nonzero value of modular weight and heavy neutral fermion mass hierarchies, which include dark matter under the A4 triplet, are uniquely determined; MX≪M2
  • Exploring neutrino mass and mass hierarchy in interacting dark energy models
    Sci.China Phys.Mech.Astron. 63 (2020) 220401

    by: Feng, Lu (Shenyang Normal U.) et al.

    We investigate how the dark energy properties impact the constraints on the total neutrino mass in interacting dark energy (IDE) models. In this study, we focus on two typical interacting dynamical dark energy models, i.e., the interacting $w$ cold dark matter (I$w$CDM) model and the interacting holographic dark energy (IHDE) model. To avoid the large-scale instability problem in IDE models, we apply the parameterized post-Friedmann approach to calculate the perturbation of dark energy. We employ the Planck 2015 cosmic microwave background temperature and polarization data, combined with low-redshift measurements on baryon acoustic oscillation distance scales, type Ia supernovae, and the Hubble constant, to constrain the cosmological parameters. We find that the dark energy properties could influence the constraint limits on the total neutrino mass. Once dynamical dark energy is considered in the IDE models, the upper bounds of $\sum m_\nu$ will be changed. By considering the values of $\chi^2_{\rm min}$, we find that in these IDE models the normal hierarchy case is slightly preferred over the inverted hierarchy case; for example, $\Delta\chi^2=2.720$ is given in the IHDE+$\sum m_\nu$ model. In addition, we also find that in the I$w$CDM+$\sum m_\nu$ model $\beta=0$ is consistent with current observational data inside the 1$\sigma$ range, and in the IHDE+$\sum m_\nu$ model $\beta>0$ is favored at more than 2$\sigma$ level.

  • Quantum correlations in neutrino oscillations in curved spacetime
    Phys.Rev. D100 (2019) 055021

    by: Dixit, Khushboo (IIT, Jodhpur) et al.

    Gravity induced neutrino-antineutrino oscillations are studied in the context of one- and two-flavor scenarios. This allows one to investigate the particle-antiparticle correlations in two and four level systems, respectively. Flavor entropy is used to probe the entanglement in the system. The well known witnesses of nonclassicality such as Mermin and Svetlichny inequalities are investigated. Since the extent of neutrino-antineutrino oscillation is governed by the strength of the gravitational field, the behavior of nonclassicality shows interesting features as one varies the strength of the gravitational field. Specifically, the suppression of the entanglement with the increase of the gravitational field is observed which is witnessed in the form of decrease in the flavor entropy of the system. The features of the Mermin and the Svetlichny inequalities allow one to make statements about the degeneracy of neutrino mass eigenstates.

  • Discovery potential of multiton xenon detectors in neutrino electromagnetic properties
    Phys.Rev. D100 (2019) 073001

    by: Hsieh, Chung-Chun (Taiwan, Natl. Taiwan U.) et al.

    Next-generation xenon detectors with multiton-year exposure are powerful direct probes of dark matter candidates, in particular the favorite weakly interacting massive particles. Coupled with the features of low thresholds and backgrounds, they are also excellent telescopes of solar neutrinos. In this paper, we study the discovery potential of ton-scale xenon detectors in electromagnetic moments of solar neutrinos. Relevant neutrino-atom scattering processes are calculated by applying a state-of-the-art atomic many-body method—relativistic random phase approximation. Limits on these moments are derived from existing data and estimated with future experiment specifications. With one ton-year exposure, XENON-1T can improve the effective millicharge constraint by a factor of 2. With LZ and DARWIN, the projected improvement on the solar neutrino effective millicharge (magnetic moment) is around 7 (2) times smaller than the current bound. If LZ can keep the same background level and push the electron recoil threshold to 0.5 keV, the projected improvement on the millicharge (magnetic moment) is about 10 (3) times smaller than the current bound. An unconventional setup of placing a strong Cr51 neutrino source by a ton-scale xenon detector is also considered.

  • Heavy neutrino searches at future $Z$-factories
    Eur.Phys.J. C79 (2019) 766

    by: Ding, Jian-Nan (Lanzhou U.) et al.

    We analyze the capacity of future Z-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos N are considered to be produced via the process $e^+e^-\rightarrow Z\rightarrow \nu N$ and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $\sigma (e^+e^-\rightarrow \nu N\rightarrow \nu \ell jj)$ given by the Z-factories with integrated luminosities of 0.1, 1 and 10 $\hbox {ab}^{-1}$ if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.

  • Flavor neutrino states for pedestrians
    J.Phys.Conf.Ser. 1275 (2019) 012023

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

    In this paper we discuss the ontology of flavor states of oscillating neutrinos. While an heuristic approach to this subject, experimentally successful in the high energy regime, is generally adopted, a logically consistent definition of flavor states describing neutrinos produced and detected in weak processes is still desirable and essential from a theoretical perspective. Here we briefly review basic facts and present some arguments which suggest that the definition of flavor states as eigenstates of flavor charges is the most reasonable one.

  • Cosmic tau neutrino detection via Cherenkov signals from air showers from Earth-emerging taus
    Phys.Rev. D100 (2019) 063010

    by: Reno, Mary Hall (Iowa U.) et al.

    We perform a new, detailed calculation of the flux and energy spectrum of Earth-emerging τ-leptons generated from the interactions of tau neutrinos and antineutrinos in the Earth. A layered model of the Earth is used to describe the variable density profile of the Earth. Different assumptions regarding the neutrino charged- and neutral-current cross sections as well as the τ-lepton energy loss models are used to quantify their contributions to the systematic uncertainty. A baseline simulation is then used to generate the optical Cherenkov signal from upward-moving extensive air showers generated by the τ-lepton decay in the atmosphere, applicable to a range of space-based instruments. We use this simulation to determine the neutrino sensitivity for Eν≳10  PeV for a space-based experiment with performance similar to that for the Probe of Extreme MultiMessenger Astrophysics (POEMMA) mission currently under study.

  • Nonuniversal $U(1)_{X}$ extension to the MSSM with three families
    Phys.Rev. D100 (2019) 055037

    by: Alvarado, J.S. (Colombia, U. Natl.) et al.

    We propose a supersymmetric extension of the anomalyfree and three families nonuniversal U(1) model, with the inclusion of four Higgs doublets and four Higgs singlets. The quark sector is extended by adding three exotic quark singlets, while the lepton sector includes two exotic charged lepton singlets, three right-handed neutrinos and three sterile Majorana neutrinos to obtain the fermionic mass spectrum. By implementing an additional Z2 symmetry, the Yukawa coupling terms are suited in such a way that the fermion mass hierarchy is obtained without fine-tuning. The effective mass matrix for SM neutrinos is fitted to current neutrino oscillation data to check the consistency of the model with experimental evidence, obtaining that the normal-ordering scheme is preferred over the inverse ones. The electron and up, down and strange quarks are massless at tree level, but they get masses through radiative correction at one loop level coming from the sleptons and Higgsinos contributions. We show that the model predicts a like-Higgs SM mass at electroweak scale by using the VEV according to the symmetry breaking and fermion masses.

  • Neutron Skin in CsI and Low-Energy Effective Weak Mixing Angle from COHERENT Data
    Phys.Rev. D100 (2019) 071301

    by: Huang, Xu-Run (Shanghai Jiaotong U., INPAC) et al.

    Both the neutron skin thickness $\Delta R_{np}$ of atomic nuclei and the low-energy neutrino-nucleon ($\nu N$) interactions are of fundamental importance in nuclear and particle physics, astrophysics as well as new physics beyond the standard model (SM) but largely uncertain currently, and the coherent elastic neutrino-nucleus scattering (CE$\nu$NS) provides a clean way to extract their information. New physics beyond the SM may cause effectively a shift of the SM weak mixing angle $\theta_W$ in low-energy $\nu N$ interactions, leading to an effective weak mixing angle $\theta^*_W$. By analyzing the CE$\nu$NS data of the COHERENT experiment, we find that while a one-parameter fit to the COHERENT data by varying $\Delta R_{np}$ produces $\Delta R^{\rm{CsI}}_{np} \simeq 0.68^{+0.91}_{-1.13}$ fm for CsI with an unrealistically large central value by fixing $\sin^2 \theta^*_W$ at the low-energy SM value of $\sin^2\theta_W^{\rm{SM}} = 0.23857$, a two-dimensional fit by varying $\Delta R_{np}$ and $\sin^2 \theta^*_W$ leads to a strong positive correlation between $\Delta R_{np}$ and $\sin^2 \theta^*_W$ with significantly smaller central values of $\Delta R^{\rm {CsI}}_{np} \simeq 0.24_{-2.03}^{+2.30}$ fm and $\sin^2 \theta^*_W = 0.21_{-0.10}^{+0.13}$. Although the uncertainty is too large to claim a determination of $\Delta R^{\rm{CsI}}_{np}$ and $\sin^2 \theta^*_W$, the present study suggests that the multi-dimensional fit is important in future analyses of high-precision CE$\nu$NS data. The implication of the possible deviation of $\sin^2 \theta^*_W$ from $\sin^2\theta_W^{\rm{SM}}$ on new physics beyond the SM is also discussed.

  • An inverse seesaw model with global $U(1)_H$ symmetry
    APCTP Pre2019- 005
    Phys.Rev. D100 (2019) 075013

    by: Dey, Ujjal Kumar (APCTP, Pohang) et al.

    We propose an inverse seesaw model based on hidden global symmetry $U(1)_H$ in which we realize tiny neutrino masses with rather natural manner taking into account relevant experimental bounds. The small Majorana mass for inverse seesaw mechanism is induced via small vacuum expectation value of a triplet scalar field whose Yukawa interactions with standard model fermions are controlled by $U(1)_H$. We discuss the phenomenology of the exotic particles present in the model including the Goldstone boson coming from breaking of the global symmetry, and explore testability at the Large Hadron Collider experiments.

  • Common explanation to the $R_{K^{(*)}}$, $R_{D^{(*)}}$ and $\epsilon^\prime/\epsilon$ anomalies in a 3HDM+$\nu_R$ and connections to neutrino physics
    Phys.Rev. D100 (2019) 055031

    by: Marzo, Carlo (NICPB, Tallinn) et al.

    Scalar theories can account for the current RD(*) measurements through a vector operator c¯LγμbLτ¯LγμνL induced at the loop level. Once the vector contribution is considered on top of a subdominant tree-level scalar component, the predicted value of RD(*) falls within the 1σ region indicated by the experiments. We explicitly demonstrate this claim in the framework of a three Higgs doublet model extended with GeV-scale right-handed neutrinos by matching the anomalous signal for perturbative values of the involved couplings and respecting the bounds from complementary flavor physics measurements. Remarkably, we furthermore show that the proposed framework can be employed to also simultaneously explain the present RK(*) measurement, as well as the deviation in ε′/ε currently being debated in the literature. These results are obtained by considering the contribution of relatively light right-handed neutrinos which are fundamental in mediating the processes behind the anomalous signals. In this way, our findings reveal a new possible connection that links the flavor anomalies to the phenomenology of extended Higgs sector and neutrino physics.

  • Effects of the standing accretion-shock instability and the lepton-emission self-sustained asymmetry in the neutrino emission of rotating supernovae
    Phys.Rev. D100 (2019) 063018

    by: Walk, Laurie (Copenhagen U.) et al.

    The rotation of core-collapse supernovae affects the neutrino emission characteristics. By comparing the neutrino properties of three three-dimensional supernova (SN) simulations of a 15  M⊙ progenitor (one nonrotating model and two models rotating at different velocities), we investigate how the neutrino emission varies with the flow dynamics in the SN core depending on the different degrees of rotation. The large-amplitude sinusoidal modulations due to the standing accretion-shock instability are weaker in both the rotating models than in the nonrotating case. The SN progenitor rotation reduces the radial velocities and radial component of the kinetic energy associated with the convection interior to the protoneutron star. This effect seems to disfavor the growth of the hemispheric neutrino-emission asymmetries associated with the lepton-emission self-sustained asymmetry. An investigation of the multipole expansion of the neutrino luminosity and the electron neutrino lepton number flux shows a dominant quadrupolar mode in rotating SN models. Our findings highlight the power of using neutrinos as probes of SN hydrodynamics.

  • What can We Learn from Triple Top-Quark Production?
    Phys.Rev. D100 (2019) 055035

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

    Different from other multiple top-quark productions, triple top-quark production requires the presence of both flavor violating neutral interaction and flavor conserving neutral interaction. We describe the interaction of triple top-quarks and up-quark in terms of two dimension-6 operators; one can be induced by a new heavy vector resonance, the other by a scalar resonance. Combining same-sign top-quark pair production and four top-quark production, we explore the potential of the 13 TeV LHC on searching for the triple top-quark production.

  • Phenomenology of TeV-scale scalar Leptoquarks in the EFT
    Phys.Rev. D100 (2019) 055020

    by: Bar-Shalom, Shaouly (Technion) et al.

    We examine new aspects of leptoquark (LQ) phenomenology using effective field theory (EFT). We construct a complete set of leading effective operators involving SU(2) singlets scalar LQ and the Standard Model fields up to dimension six. We show that, while the renormalizable LQ-lepton-quark interaction Lagrangian can address the persistent hints for physics beyond the Standard Model in the B-decays B¯→D(*)τν¯, B¯→K¯ℓ+ℓ- and in the measured anomalous magnetic moment of the muon, the LQ higher dimensional effective operators may lead to new interesting effects associated with lepton number violation. These include the generation of one-loop and two-loops sub-eV Majorana neutrino masses, mediation of neutrinoless double-β decay and novel LQ collider signals. For the latter, we focus on third generation LQ (ϕ3) in a framework with an approximate Z3 generation symmetry and show that one class of the dimension five LQ operators may give rise to a striking asymmetric same-charge ϕ3ϕ3 pair-production signal, which leads to low background same-sign leptons signals at the LHC. For example, with Mϕ3∼1  TeV and a new physics scale of Λ∼5  TeV, we expect at the 13 TeV LHC with an integrated luminosity of 300  fb-1, about 5000 positively charged τ+τ+ events via pp→ϕ3ϕ3→τ+τ++2·jb (jb=b-jet), about 500 negatively charged τ-τ- events with a signature pp→ϕ3ϕ3→τ-τ-+4·j+2·jb (j=light jet) and about 50 positively charged ℓ+ℓ+ events via pp→ℓ+ℓ++2·jb+ET for any of the three charged leptons, ℓ+ℓ+=e+e+,μ+μ+,τ+τ+. It is interesting to note that, in the LQ EFT framework, the expected same-sign lepton signals have a rate which is several times larger than the QCD LQ-mediated opposite-sign leptons signals, gg,qq¯→ϕ3ϕ3*→ℓ+ℓ-+X. We also consider the same-sign charged lepton signals in the LQ EFT framework at higher energy hadron colliders such as a 27 TeV HE-LHC and a 100 TeV FCC-hh.

  • Dark matter and LHC phenomenology of a scale invariant scotogenic model
    Chin.Phys. C43 (2019) 103102

    by: Guo, Chao (Nankai U.) et al.

    We study the phenomenology of a model that addresses the neutrino mass, dark matter, and generation of the electroweak scale in a single framework. Electroweak symmetry breaking is realized via the Coleman-Weinberg mechanism in a classically scale invariant theory, while the neutrino mass is generated radiatively through interactions with dark matter in a typically scotogenic manner. The model introduces a scalar triplet and singlet and a vector-like fermion doublet that carry an odd parity of , and an even parity scalar singlet that helps preserve classical scale invariance. We sample over the parameter space by taking into account various experimental constraints from the dark matter relic density and direct detection, direct scalar searches, neutrino mass, and charged lepton flavor violating decays. We then examine by detailed simulations possible signatures at the LHC to find some benchmark points of the free parameters. We find that the future high-luminosity LHC will have a significant potential in detecting new physics signals in the dilepton channel.

  • The Giant Radio Array for Neutrino Detection (GRAND): Science and Design
    Sci.China Phys.Mech.Astron. 63 (2020) 219501

    by: Álvarez-Muñiz, Jaime (Santiago de Compostela U.) et al.

    The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 10^8 GeV. Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays. To do this, GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity. GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere. Its design is modular: 20 separate, independent sub-arrays, each of 10 000 radio antennas deployed over 10 000 km^2. A staged construction plan will validate key detection techniques while achieving important science goals early. Here we present the science goals, detection strategy, preliminary design, performance goals, and construction plans for GRAND.

  • Inflation, (P)reheating and Neutrino Anomalies: Production of Sterile Neutrinos with Secret Interactions
    Eur.Phys.J. C79 (2019) 818

    by: Paul, Arnab (Indian Statistical Inst., Calcutta) et al.

    A number of experimental anomalies involving neutrinos hint towards the existence of at least an extra (a very light) sterile neutrino. However, such a species, appreciably mixing with the active neutrinos, is disfavored by different cosmological observations like Big Bang Nucleosynthesis (BBN), Cosmic Microwave Background (CMB) and Large Scale Structure (LSS). Recently, it was shown that the presence of additional interactions in the sterile neutrino sector via light bosonic mediators can make the scenario cosmologically viable by suppressing the production of the sterile neutrinos from active neutrinos via matter-like effect caused by the mediator. This mechanism works assuming the initial population of this sterile sector to be negligible with respect to that of the Standard Model (SM) particles, before the production from active neutrinos. However, there is fair chance that such bosonic mediators may couple to the inflaton and can be copiously produced during (p)reheating epoch. Consequently, they may ruin this assumption of initial small density of the sterile sector. In this article we, starting from inflation, investigate the production of such a sterile sector during (p)reheating in a large field inflationary scenario and identify the parameter region that allows for a viable early Universe cosmology.

  • DUNE as the Next-Generation Solar Neutrino Experiment
    Phys.Rev.Lett. 123 (2019) 131803

    by: Capozzi, Francesco (Ohio State U., CCAPP) et al.

    We show that the Deep Underground Neutrino Experiment (DUNE), with significant but feasible new efforts, has the potential to deliver world-leading results in solar neutrinos. With a 100  kton-yr exposure, DUNE could detect ≳105 signal events above 5 MeV electron energy. Separate precision measurements of neutrino-mixing parameters and the B8 flux could be made using two detection channels (νe+Ar40 and νe,μ,τ+e-) and the day-night effect (>10σ). New particle physics may be revealed through the comparison of solar neutrinos (with matter effects) and reactor neutrinos (without), which is discrepant by ∼2σ (and could become 5.6σ). New astrophysics may be revealed through the most precise measurement of the B8 flux (to 2.5%) and the first detection of the hep flux (to 11%). DUNE is required: No other experiment, even proposed, has been shown capable of fully realizing these discovery opportunities.

  • Long-Lived Particles at the Energy Frontier: The MATHUSLA Physics Case
    Rept.Prog.Phys. 82 (2019) 116201

    by: Curtin, David (Toronto U.) et al.

    We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of Standard Model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the $\mu$m scale up to the Big Bang Nucleosynthesis limit of $\sim 10^7$m. Neutral LLPs with lifetimes above $\sim$ 100m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging backgrounds, triggers, and small acceptances. MATHUSLA is a proposal for a minimally instrumented, large-volume surface detector near ATLAS or CMS. It would search for neutral LLPs produced in HL-LHC collisions by reconstructing displaced vertices (DVs) in a low-background environment, extending the sensitivity of the main detectors by orders of magnitude in the long-lifetime regime. In this white paper we study the LLP physics opportunities afforded by a MATHUSLA-like detector at the HL-LHC. We develop a model-independent approach to describe the sensitivity of MATHUSLA to BSM LLP signals, and compare it to DV and missing energy searches at ATLAS or CMS. We then explore the BSM motivations for LLPs in considerable detail, presenting a large number of new sensitivity studies. While our discussion is especially oriented towards the long-lifetime regime at MATHUSLA, this survey underlines the importance of a varied LLP search program at the LHC in general. By synthesizing these results into a general discussion of the top-down and bottom-up motivations for LLP searches, it is our aim to demonstrate the exceptional strength and breadth of the physics case for the construction of the MATHUSLA detector.

  • Quantum Decoherence Effects in Neutrino Oscillations at DUNE
    Phys.Rev. D100 (2019) 055023

    by: Balieiro Gomes, G. (Campinas State U.) et al.

    In this work, we analyze quantum decoherence in neutrino oscillations considering the open quantum system framework and oscillations through matter for three-neutrino families. Taking the Deep Underground Neutrino Experiment as a case study, we performed sensitivity analyses for two neutrino flux configurations, finding sensitivity limits for the decoherence parameters. We also offer a physical interpretation for a new peak which arises at the νe appearance probability with decoherence. The sensitivity limits found for the decoherence parameters are Γ21≤1.2×10-23  GeV and Γ32≤7.7×10-25  GeV at 90% C.L.

  • Flavour composition and entropy increase of cosmological neutrinos after decoherence
    Universe 5 (2019) 203

    by: Boriero, Daniel (Bielefeld U.) et al.

    We investigate the evolution of the flavour composition of the cosmic neutrino background from neutrino decoupling until today. The decoherence of neutrino mass states is described by means of Lindblad operators. Decoherence goes along with the increase of neutrino family entropy, which we obtain as a function of initial spectral distortions, mixing angles and CP-violation phase. We also present the expected flavour composition of the cosmic neutrino background after decoherence is completed. Decoherence is proposed to happen after the two heaviest neutrino mass states become non-relativistic. We discuss how the associated increase of entropy could be observed (in principle). The physics of two- or three-flavour oscillation of cosmological neutrinos resembles in many aspects two- or three-level systems in atomic clocks, which were recently proposed by Weinberg for the study of decoherence phenomena.

  • Lepton flavor violating processes in the minimal 3-3-1 model with singlet sterile neutrinos
    J.Phys. G46 (2019) 115005

    by: Machado, A.C.B. (Sao Paulo, IFT) et al.

    We consider the minimal 3-3-1 model with three sterile neutrinos transforming as singlet under the $SU(3)_L\otimes U(1)_X$ symmetry. This model, with or without sterile neutrinos, predicts flavor violating interactions in both quark and lepton sectors, since all the charged fermions mass matrices can not be assumed diagonal in any case. Here we accommodate the lepton masses and the Pontecorvo-Maki-Nakawaga-Sakata matrix at the same time, and as consequence the Yukawa couplings and the unitary matrices which diagonalize the mass matrices are not free parameters anymore. We study some phenomenological consequences, i.e., $l_i\to l_jl_k \bar{l}_k$ and $l_i\to l_j\gamma$ which are induced by neutral and doubly charged particles present in the model. In particular we find that if the decay $\mu\to ee\bar{e}$ is observed in the future, the only particle in the model that could explain this decay is the doubly charged vector bilepton.

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