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  • Possible Explanation of the Geograv Detector Signal during the Explosion of SN 1987A in Modified Gravity Models
    J.Exp.Theor.Phys. 128 (2019) 599-606

    by: Eroshenko, Yu.N. (Moscow, INR) et al.

    A change in the law of attraction in some regimes is predicted in the modified gravity models being actively developed at present. The set of up-to-date observational data leaves a wide range of admissible parameters for the theory. In this paper, we consider the possibility that the signal recorded by the Geograv resonant gravitational-wave detector in 1987 during the explosion of SN 1987A was produced by an abrupt change in the metric during the passage of a powerful neutrino flux through the detector. Such an impact on the detector is possible, in particular, in extended scalar–tensor theories in which the local matter density gradient affects the gravitational force. The first short neutrino pulse emitted at the initial stage of stellar core collapse before the onset of neutrino opacity could exert a major influence on the detector, because it could produce the detector response at the first resonance frequency. In contrast, the influence of the subsequent broad pulse (with a duration of several seconds) in the resonant detector is exponentially suppressed, despite the fact that the second pulse carries an order-of-magnitude more neutrino energy, and it could generate a signal in the LSD neutrino detector. This explains the time delay of 1.4 s between the Geograv and LSD signals. The consequences of this effect of modified gravity for future LIGO/Virgo observations are discussed.

  • Determination of CP violation in the lepton sector
    AIP Conf.Proc. 2109 (2019) 110004

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

    Determination of leptonic CP violation is one of the open and most challenging problems in particle physics. Observation of neutrino oscillation, in particular, a non-zero value of the third neutrino mixing angle, has facilitated the possibility of determination of the parameter characterizing CP violation. In this paper we introduce CP violation and discuss the possibility of measuring the CP violation parameter from current and future neutrino oscillation experiments. We include some recent results obtained in this direction.

  • Strongly Interacting Neutrino Portal Dark Matter

    by: Lamprea, J.M.
    We present a realistic, simple and natural model of strongly-interacting dark matter based on the neutrino-portal paradigm. The strong interactions at small velocities are generated by the exchange of dark photons, and produce the observed core-like DM distribution in galactic centers; this effect could be spoiled by the formation of DM bound states (also due to dark-photon effects), which we avoid by requiring the DM candidates to be light, with masses below O(10 GeV). The mixing of the dark photon with the Z and ordinary photon is strongly suppressed by introducing a softly-broken discrete symmetry similar to charge conjugation, which also ensures that the dark photon life-time is short enough to avoid restrictions derived form big-bang nucleosynthesis and large-scale structure formation. Other constraints are accommodated without the need of fine tuning, in particular nucleon scattering occurs only at one loop, so direct detection cross sections are naturally suppressed. Neutrino masses are generated through the inverse see saw.

  • Magnetic field effects on neutrino oscillations

    by: Erdas, Andrea
    Using the exact propagators in a constant magnetic field, the neutrino self-energy has been calculated to all orders in the field strength $B$ within the minimal extension of the Weinberg-Salam model with massive Dirac neutrinos. A neutrino dispersion relation, effective potential and effective mass have been obtained that depend on $B$. The consequences of this effective potential on neutrino oscillations have been explored, and resonance conditions have been obtained for magnetic fields $0
  • Multiple modular symmetries as the origin of flavour

    by: de Medeiros Varzielas, Ivo
    We develop a general formalism for multiple moduli and their associated modular symmetries. We apply this formalism to an example based on three moduli with finite modular symmetries $S_4^A$, $S_4^B$ and $S_4^C$, associated with two right-handed neutrinos and the charged lepton sector, respectively. The symmetry is broken by two bi-triplet scalars to the diagonal $S_4$ subgroup. The low energy effective theory involves the three independent moduli fields $\tau_A$, $\tau_B$ and $\tau_C$, which preserve the residual modular subgroups $Z_3^A$, $Z_2^B$ and $Z_3^C$, in their respective sectors, leading to trimaximal TM$_1$ lepton mixing, consistent with current data, without flavons.

  • Nuclear Effects and CP Sensitivity at DUNE

    by: Nagu, Srishti
    The precise measurement of neutrino oscillation parameters is one of the highest priorities in neutrino oscillation physics. To achieve the desired precision, it is necessary to reduce the systematic uncertainties related to neutrino energy reconstruction. An error in energy reconstruction is propagated to all the oscillation parameters, hence a careful estimation of neutrino energy is required. To increase the statistics, neutrino oscillation experiments use heavy nuclear targets like Argon(Z=18). The use of these nuclear targets introduces nuclear effects that severely impact the neutrino energy reconstruction which in turn poses influence in the determination of neutrino oscillation parameters. In this work, we have tried to quantify nuclear effects on the determination of CP phase at DUNE using final state interactions.

  • A near-minimal leptoquark model for reconciling flavour anomalies and generating radiative neutrino masses

    by: Bigaran, Innes
    We introduce two scalar leptoquarks, the SU$(2)_L$ isosinglet denoted $\phi\sim(\mathbf{3}, \mathbf{1}, -1/3)$ and the isotriplet $\varphi\sim(\mathbf{3}, \mathbf{3}, -1/3)$, to explain observed deviations from the standard model in semi-leptonic $B$-meson decays. We explore the regions of parameter space in which this model accommodates the persistent tensions in the decay observables $R_{D^{(*)}}$, $R_{K^{(*)}}$, and angular observables in $b\to s \mu\mu$ transitions. Additionally, we exploit the role of these exotics in existing models for one-loop neutrino mass generation derived from $\Delta L=2$ effective operators. Introducing the vector-like quark $\chi \sim (\mathbf{3}, \mathbf{2}, -5/6)$ necessary for lepton-number violation, we consider the contribution of both leptoquarks to the generation of radiative neutrino mass. We find that constraints permit simultaneously accommodating the flavour anomalies while also explaining the relative smallness of neutrino mass without the need for cancellation between leptoquark contributions. A characteristic prediction of our model is a rate of muon--electron conversion in nuclei fixed by the anomalies in $b \to s \mu \mu$ and neutrino mass; the COMET experiment will thus test and potentially falsify our scenario. The model also predicts signatures that will be tested at the LHC and Belle II.

  • Signatures of Supersymmetry in Neutrino Telescopes

    by: Dev, P.S. Bhupal
    We review the prospects of probing $R$-parity violating Supersymmetry (RPV SUSY) at neutrino telescopes using some of the highest energy particles given to us by Nature. The presence of RPV interactions involving ultra-high energy neutrinos with Earth-matter can lead to resonant production of TeV-scale SUSY partners of the SM quarks and leptons (squarks and sleptons), thereby giving rise to potentially anomalous behavior in the event spectrum observed by large-volume neutrino detectors, such as IceCube, as well as balloon-borne cosmic ray experiments, such as ANITA. Using the ultra-high energy neutrino events observed recently at IceCube, with the fact that for a given power-law flux of astrophysical neutrinos, there is no statistically significant deviation in the current data from the Standard Model expectations, we derive robust upper limits on the RPV couplings as a function of the resonantly-produced squark mass, independent of the other unknown model parameters, as long as the squarks decay dominantly to two-body final states involving leptons and quarks through the RPV couplings. Also, we discuss RPV SUSY interpretations of the recent anomalous, upward-going EeV air showers observed at ANITA, in terms of long-lived charged or neutral next-to-lightest SUSY particles.

  • Searches for magnetic monopoles and others stable massive particles

    by: Spurio, Maurizio
    The Standard Model (SM) of the microcosm provides an excellent description of the phenomena of the microcosm, with the triumph of the discovery of the Higgs boson. There are many reasons, however, to believe that the SM is incomplete and represents a valid theory at relatively low energies only. Of particular interest are the models based on complete symmetries, such as those attempting a true unification between leptons and quarks in terms of a single symmetry group (Grand Unified Theories, GUTs) and those attempting unification between fermions and bosons, such as the supersymmetry. This chapter is devoted to the description of stable and massive particles not predicted within the SM, their energy loss mechanisms and their searches in the cosmic radiation. The stability of these particles means that if they were produced at any time in the thermal history of the Universe, they would still be present as relic particles. Examples of stable massive particles discussed in this chapter include magnetic monopoles, strange quark matter and supersymmetric particles. In particular, we focus on the status of searches for magnetic monopoles (also inducing proton-decay processes), nuclearites and Q-balls in neutrino telescopes.

  • Neutrino oscillations in a trapping potential

    by: Johns, Lucas
    A number of derivations of the standard neutrino oscillation formula are known, each one providing its own unique insights. Common to all treatments is the assumption that neutrinos propagate freely between source and detector, as indeed they do in all experiments thus far conducted. Here we consider how neutrinos oscillate when, contrary to the usual set-up, they are bound in a potential well. The focus in particular is on nonrelativistic neutrinos with quasi-degenerate masses, for which oscillations in free space are described by the same formula, to lowest order, as relativistic neutrinos. Trapping these particles engenders corrections to their oscillation frequencies because the interference terms are between discrete energy levels rather than continuous spectra. Especially novel is the frequency shift that occurs due to the dependence of the energy levels on the mass of the neutrino: this part of the correction is nonvanishing even in the extremely nonrelativistic limit, reflecting the fact that the neutrino mass states have different zero-point energies in the well. Building an apparatus that can trap neutrinos is a futuristic prospect to say the least, but these calculations nonetheless shine a light on certain basic aspects of the flavor-oscillation phenomenon.

  • Icecube/DeepCore tests for novel explanations of the MiniBooNE anomaly

    by: Coloma, Pilar
    While the low-energy excess observed at MiniBooNE remains unchallenged, it has become increasingly difficult to reconcile it with the results from other sterile neutrino searches and cosmology. Recently, it has been shown that non-minimal models with new particles in a hidden sector could provide a better fit to the data. As their main ingredients they require a GeV-scale $Z'$, kinetically mixed with the photon, and an unstable heavy neutrino with a mass in the 150 MeV range that mixes with the light neutrinos. In this letter we point out that atmospheric neutrino experiments (and, in particular, IceCube/DeepCore) could probe a significant fraction of the parameter space of such models by looking for an excess of "double-bang" events at low energies, as proposed in our previous work (arXiv:1707.08573). Such a search would probe exactly the same production and decay mechanisms required to explain the anomaly.

  • Transition Probabilities in the Two-Level System with PT-Symmetric Non-Hermitian Hamiltonians

    by: Ohlsson, Tommy (Royal Inst. Tech., Stockholm) et al.

    In this work, we investigate how to define in a consistent way the probabilities of the transitions between the "flavor" states of the two-level quantum system, which is described by a non-Hermitian but parity and time-reversal (PT) symmetric Hamiltonian. Explicit calculations are carried out to demonstrate the conservation of probability if a proper definition of the final state is adopted. Finally, this formalism is applied to two-flavor neutrino oscillations $\nu^{}_\mu \to \nu^{}_\mu$ and $\nu^{}_\mu \to \nu^{}_\tau$ in vacuum, where the exact PT symmetry requires the vacuum mixing angle to be maximal, which is compatible with current neutrino oscillation experiments. A possible generalization to the three-flavor case is briefly discussed.

  • A low scale type I seesaw model for lepton masses and mixings

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

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

  • CP violating effects in coherent elastic neutrino-nucleus scattering processes

    by: Aristizabal Sierra, D. (Santa Maria U., Valparaiso) et al.

    The presence of new neutrino-quark interactions can enhance, deplete or distort the coherent elastic neutrino-nucleus scattering (CEvNS) event rate. The new interactions may involve CP violating phases that can potentially affect these features. Assuming light vector mediators, we study the effects of CP violation on the CEvNS process in the COHERENT sodium-iodine, liquid argon and germanium detectors. We identify a region in parameter space for which the event rate always involves a dip and another one for which this is never the case. We show that the presence of a dip in the event rate spectrum can be used to constraint CP violating effects, in such a way that the larger the detector volume the tighter the constraints. Furthermore, it allows the reconstruction of the effective coupling responsible for the signal with an uncertainty determined by recoil energy resolution. In the region where no dip is present, we find that CP violating parameters can mimic the Standard Model CEvNS prediction or spectra induced by real parameters. We point out that the interpretation of CEvNS data in terms of a light vector mediator should take into account possible CP violating effects. Finally, we stress that our results are qualitatively applicable for CEvNS induced by solar or reactor neutrinos. Thus, the CP violating effects discussed here and their consequences should be taken into account as well in the analysis of data from multi-ton dark matter detectors or experiments such as CONUS, $\nu$-cleus or CONNIE.

  • Where Are We With Light Sterile Neutrinos?

    by: Diaz, A. (MIT) et al.

    We review the status of searches for sterile neutrinos in the $\sim 1$ eV range, with an emphasis on the latest results from short baseline oscillation experiments and how they fit within sterile neutrino oscillation models. We present global fit results to a three-active-flavor plus one-sterile-flavor model (3+1), where we find an improvement of $\Delta \chi^2=35$ for 3 additional parameters compared to a model with no sterile neutrino. This is a 5$\sigma$ improvement, indicating that an effect that is like that of a sterile neutrino is highly preferred by the data. However we note that separate fits to the appearance and disappearance oscillation data sets within a 3+1 model do not show the expected overlapping allowed regions in parameter space. This ``tension'' leads us to explore two options: 3+2, where a second additional mass state is introduced, and a 3+1+decay model, where the $\nu_4$ state can decay to invisible particles. The 3+1+decay model, which is also motivated by improving compatibility with cosmological observations, yields the larger improvement, with a $\Delta \chi^2=8$ for 1 additional parameter beyond the 3+1 model, which is a $2.6\sigma$ improvement. Moreover the tension between appearance and disappearance experiments is reduced compared to 3+1, although disagreement remains. In these studies, we use a frequentist approach and also a Bayesean method of finding credible regions. With respect to this tension, we review possible problems with the global fitting method. We note multiple issues, including problems with reproducing the experimental results, especially in the case of experiments that do not provide data releases. We discuss an unexpected 5 MeV excess, observed in the reactor flux energy spectrum, that may be affecting the oscillation interpretation of the short baseline reactor data. We emphasize the care that must be taken in mapping to the true neutrino energy in the case of oscillation experiments that are subject to multiple interaction modes and nuclear effects. We point to problems with the ``Parameter-Goodness-of-Fit test'' that is used to quantify the tension. Lastly, we point out that analyses presenting limits often receive less scrutiny that signals. While we provide a snapshot of the status of sterile neutrino searches today and global fits to their interpretation, we emphasize that this is a fast-moving field. We briefly review experiments that are expected to report new data in the immediate future. Lastly, we consider the 5-year horizon, where we propose that decay-at-rest neutrino sources are the best method of finally resolving the confusing situation.

  • Effect of extended $\nu$ production region on collective oscillations in supernovae

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

    In supernovae neutrinos are emitted from a region with a width $r_{\rm eff}$ of a few kilometres (rather than from a surface of infinitesimal width). We study the effect of integration (averaging) over such an extended emission region on collective oscillations. The averaging leads to additional suppression of the correlation (off-diagonal element of the density matrix) by a factor $\sim 1/r_{\rm eff} V_e \sim 10^{-10}$ where $V_e$ is the matter potential. This factor enters the initial condition for further collective oscillations and, consequently, leads to a delay of the strong flavour transitions. We justify and quantify this picture using a simple example of collective effects in two intersecting fluxes. We have derived the evolution equation for the density matrix elements integrated over the emission region and solved it both numerically and analytically. For the analytic solution we have used linearised equations. We show that the delay of the development of the instability and the collective oscillations depends on the suppression factor due to the averaging (integration) logarithmically. If the instability develops inside the production region, the integration leads not only to a delay but also to a modification of the exponential grow.

  • Towards unification of quark and lepton flavors in $A_4$ modular invariance
    APCTP Pre2019-011

    by: Okada, Hiroshi (APCTP, Pohang) et al.

    We study quark and lepton mass matrices in the $A_4$ modular invariance towards the unification of the quark and lepton flavors. We adopt modular forms of weights $2$ and $6$ for the quarks and charged leptons while we use modular forms of weight $4$ for the neutrino mass matrix generated by the Weinberg operator. The modulus $\tau$ is common in both quark and lepton mass matrices. We obtain the successful quark mass matrices, in which the down-type quark mass matrix is constructed by modular forms of weight $2$, but the up-type quark mass matrix is constructed by modular forms of weight $6$. Inputting observed masses and flavor mixing of quarks and leptons, model parameters are almost fixed as well as the value of modulus $\tau$. Supposing that the charged lepton mass matrix is constructed by modular forms of weight $2$, $\sin^2\theta_{23}$ is predicted around $0.46$--$0.47$ for the normal hierarchy of neutrino masses. The CP violating Dirac phase is also predicted as $\delta_{CP}^\ell=100^\circ$--$ 120^\circ $ or $240^\circ$--$260^\circ$, which is mainly originated from the modulus $\tau$. The effective neutrino mass of the $0\nu\beta\beta$ decay is $\langle m_{ee}\rangle=4$--$18$meV and the sum of neutrino masses is $90$meV. The inverted hierarchy of neutrino masses is excluded in our scheme of the $A_4$ modular invariance. These predictions will be tested in the near future neutrino experiments.

  • Probing the Majorana Nature in Radiative Neutrino mass models with the same-sign dilepton final states at future colliders

    by: Soualah, Rachik (KUSTAR, Sharjah) et al.

    Neutrinos in the Standard Model (SM) are considered to be massless which is in contradiction with the evidence from the neutrino oscillation data. These experiments established that at least two SM neutrinos have non-zero masses and that individual lepton numbers are violated. This is strong evidence of new physics beyond the SM that should be responsible for generating non zero mass for the neutrinos. In this work, we study the collider phenomenology of an extension of the SM where neutrinos are generated radiatively at three-loop. We show that the production of same-sign dilepton at lepton colliders (such as FCC-ee and ILC) can be used to probe the Majorana nature of neutrinos in this class of models.

  • Exact solution of quantum many-body collective neutrino flavor oscillations

    by: Rrapaj, Ermal (UC, Berkeley)

    I study the flavor evolution of a dense neutrino gas by considering vacuum contributions, matter effects and neutrino self-interactions. Assuming a system of two flavors in a uniform matter background, the time evolution of the many-body system in discretized momentum space is computed. Here neutrino-neutrino interactions are treated exactly and compared to both the single-angle approximation and mean field calculations. The mono-energetic two neutrino beam scenario is solved analytically which allows for direct comparison among these methods. I find fast collective oscillations that develop when neutrinos of each flavor are present in comparable amounts. This is not seen in the mean field treatment. The difference can be ascribed to non-negligible flavor polarization correlations being present. I proceed to solve flavor oscillations for mono-energetic cubic lattices and quadratic lattices of two energy levels. Fast collective oscillations develop even when neutrinos of different energies interact provided both flavors are present. In agreement with the two beam scenario, the mean field treatment shows no collective oscillations. In future work, I intend to include anti-neutrinos and use larger lattices.

  • Impact of Cross-Sectional Uncertainties on DUNE Sensitivity due to Nuclear Effects

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

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

  • Type-I Seesaw as the Common Origin of Neutrino Mass, Baryon Asymmetry, and the Electroweak Scale

    by: Brdar, Vedran (Heidelberg, Max Planck Inst.) et al.

    The type-I seesaw represents one of the most popular extensions of the Standard Model. Previous studies of this model have mostly focused on its ability to explain neutrino oscillations as well as on the generation of the baryon asymmetry via leptogenesis. Recently, it has been pointed out that the type-I seesaw can also account for the origin of the electroweak scale due to heavy-neutrino threshold corrections to the Higgs potential. In this paper, we show for the first time that all of these features of the type-I seesaw are compatible with each other. Integrating out a set of heavy Majorana neutrinos results in small masses for the Standard Model neutrinos; baryogenesis is accomplished by resonant leptogenesis; and the Higgs mass is entirely induced by heavy-neutrino one-loop diagrams, provided that the tree-level Higgs potential satisfies scale-invariant boundary conditions in the ultraviolet. The viable parameter space is characterized by a heavy-neutrino mass scale roughly in the range $10^{6.5\cdots7.0}$ GeV and a mass splitting among the nearly degenerate heavy-neutrino states up to a few TeV. Our findings have interesting implications for high-energy flavor models and low-energy neutrino observables. We conclude that the type-I seesaw sector might be the root cause behind the masses and cosmological abundances of all known particles. This statement might even extend to dark matter in the presence of a keV-scale sterile neutrino.

  • Leptogenesis in the Neutrino Option

    by: Brivio, I. (Heidelberg U.) et al.

    We examine the compatibility between the Neutrino Option, in which the electroweak scale is generated by PeV mass type I seesaw Majorana neutrinos, and leptogenesis. We find the Neutrino Option is consistent with resonant leptogenesis. Working within the minimal seesaw scenario with two heavy Majorana neutrinos $N_{1,2}$, which form a pseudo-Dirac pair, we explore the viable parameter space. We find that the Neutrino Option and successful leptogenesis are compatible in the cases of a neutrino mass spectrum with normal (inverted) ordering for $1.2 \times 10^6 < M \text{ (GeV)} < 8.8 \times 10^6$ ($2.4 \times 10^6 < M \text{ (GeV)} < 7.4 \times 10^6$), with $M = (M_1 + M_2)/2$ and $M_{1,2}$ the masses of $N_{1,2}$. Successful leptogenesis requires that $\Delta M/M \equiv (M_2 - M_1)/M \sim 10^{-8}$. We further show that leptogenesis can produce the baryon asymmetry of the Universe within the Neutrino Option scenario when the requisite CP violation in leptogenesis is provided exclusively by the Dirac or Majorana low energy CP violation phases of the PMNS matrix.

  • Confronting Tri-direct CP-symmetry models to neutrino oscillation experiments

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

    Tri-direct CP symmetry is an economical neutrino model building paradigm, and it allows to describe neutrino masses, mixing angles and CP violation phases in terms of four free parameters. Viability of a class of tri-direct CP models is examined with a comprehensive simulation of current and future neutrino oscillation experiments. Two benchmark models as well as the full parameter space are carefully scanned, and the parameter degeneracy problem is observed from the constraint of one group of neutrino oscillation experiments. Complementary roles from the accelerator neutrino experiments (e.g., T2HK and DUNE) and reactor neutrino experiments (e.g., JUNO) are crucial to break the degeneracy and nail down fundamental neutrino mixing parameters of the underlying theory.

  • Higgs Parity Grand Unification

    by: Hall, Lawrence J. (UC, Berkeley) et al.

    The vanishing of the Higgs quartic coupling of the Standard Model at high energies may be explained by spontaneous breaking of Higgs Parity. Taking Higgs Parity to originate from the Left-Right symmetry of the $SO(10)$ gauge group, leads to a new scheme for precision gauge coupling unification that is consistent with proton decay. We compute the relevant running of couplings and threshold corrections to allow a precise correlation among Standard Model parameters. The scheme has a built-in solution for obtaining a realistic value for $m_b/m_\tau$, which further improves the precision from gauge coupling unification, allowing the QCD coupling constant to be predicted to the level of 1 % or, alternatively, the top quark mass to 0.2 %. Future measurements of these parameters may significantly constrain the detailed structure of the theory. We also study an $SO(10)$ embedding of quark and lepton masses, showing how large neutrino mixing is compatible with small quark mixing, and predict a normal neutrino mass hierarchy. The strong CP problem may be explained by combining Higgs Parity with space-time parity.

  • CP Symmetries as Guiding Posts: revamping tri-bi-maximal Mixing. Part II

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

    In this follow up of arXiv:1812.04663 we analyze the generalized CP symmetries of the charged lepton mass matrix compatible with the complex version of the Tri-Bi-Maximal (TBM) lepton mixing pattern. These symmetries are used to `revamp' the simplest TBM \textit{Ansatz} in a systematic way. Our generalized patterns share some of the attractive features of the original TBM matrix and are consistent with current oscillation experiments. We also discuss their phenomenological implications both for upcoming neutrino oscillation and neutrinoless double beta decay experiments.

  • Two component dark matter with inert Higgs doublet: neutrino mass, high scale validity and collider searches

    by: Bhattacharya, Subhaditya (Indian Inst. Tech., Guwahati) et al.

    The idea of this work is to investigate the constraints on the dark matter (DM) allowed parameter space from high scale validity (absolute stability of Higgs vacuum and perturbativity) in presence of multi particle dark sector and heavy right handed neutrinos to address correct neutrino mass. We illustrate a simple dark sector, consisting of one inert $SU(2)_L$ scalar doublet and a scalar singlet, both stabilised by additional $\mathcal{Z}_2 \times \mathcal{Z}^{'}_2$ symmetry, which aid to vacuum stability. We demonstrate DM-DM interaction helps achieving a large allowed paramete space for both the DM components by evading direct search bound. But, high scale validity puts further constraints on the model, for example, on the mass splitting between the charged and neutral component of inert doublet, which has important implication to its leptonic signature(s) at the Large Hadron Collider (LHC).

  • Dark matter and baryon-number generation in quintessential inflation via hierarchical right-handed neutrinos

    by: Hashiba, Soichiro (Tokyo U.) et al.

    Incorporating three generations of right-handed Majorana neutrinos to quintessential inflation, we construct a model which simultaneously explains inflation, dark energy, dark matter and baryogenesis. These neutrinos have hierarchical masses $M_3 \sim 10^{13}$GeV, $M_2 \sim 10^{11}$GeV, $M_1 \sim 10$keV and are produced by gravitational particle production in the kination regime after inflation. The heaviest, the intermediate, and the lightest account for reheating, CP violation of leptogenesis, and dark matter, respectively. This model can be tested in various ways with forthcoming observations.

  • Data-Driven Modeling of Electron Recoil Nucleation in PICO C$_3$F$_8$ Bubble Chambers

    by: Amole, C. (Queen's U., Kingston) et al.

    The primary advantage of moderately superheated bubble chamber detectors is their simultaneous sensitivity to nuclear recoils from WIMP dark matter and insensitivity to electron recoil backgrounds. A comprehensive analysis of PICO gamma calibration data demonstrates for the first time that electron recoils in C$_3$F$_8$ scale in accordance with a new nucleation mechanism, rather than one driven by a hot-spike as previously supposed. Using this semi-empirical model, bubble chamber nucleation thresholds may be tuned to be sensitive to lower energy nuclear recoils while maintaining excellent electron recoil rejection. The PICO-40L detector will exploit this model to achieve thermodynamic thresholds as low as 2.8 keV while being dominated by single-scatter events from coherent elastic neutrino-nucleus scattering of solar neutrinos. In one year of operation, PICO-40L can improve existing leading limits from PICO on spin-dependent WIMP-proton coupling by nearly an order of magnitude for WIMP masses greater than 3 GeV c$^{-2}$ and will have the ability to surpass all existing non-xenon bounds on spin-independent WIMP-nucleon coupling for WIMP masses from 3 to 40 GeV c$^{-2}$.

  • Heavy neutrino production via $Z'$ at the lifetime frontier

    by: Deppisch, Frank (University Coll. London) et al.

    We investigate the pair production of right-handed neutrinos from the decay of an additional neutral $Z^{\prime}$ boson in the gauged $B-L$ model. Taking into account current constraints on the $Z^{\prime}$ mass and the associated gauge coupling $g_{1}^{\prime}$, we analyse the sensitivity of proposed experiments at the lifetime frontier, FASER 2, CODEX-b, MATHUSLA as well as a hypothetical version of the MAPP detector to a long lived heavy neutrino $N$ originating in the decays of the $Z^{\prime}$. We further complement this study with determining the reach of LHCb and a CMS-type detector for the high-luminosity LHC run. We demonstrate that in a background free scenario with $g_1^\prime = 10^{-3}$ near the current limit, FASER 2 is sensitive to the active-sterile neutrino mixing down to $V_{\mu N} \approx 10^{-4}$, while a reach of $V_{\mu N} \approx 10^{-5}$ can be obtained for CODEX-b and LHCb, in a mass regime of $m_N \approx 5-20$ GeV and $m_{Z^{\prime}} \approx 20-70$ GeV. Finally, MATHUSLA can probe $V_{\mu N} \approx 10^{-7}$ and cover the mixing regime expected in a canonical seesaw scenario of light neutrino mass generation.

  • Hidden relations in three generation seesaw model with Dirac mass matrix of four-zero texture

    by: Morozumi, Takuya (Hiroshima U.) et al.

    We present predictions for CP violating phases of the Type-I seesaw model with four-zero textures on the Dirac mass matrix. For the four-zero textures, the effective low energy Majorana mass matrix is parametrized with seven parameters. They are three mass-dimensional parameters, two angles and two CP violating sources. The number of these parameters is less than that of the general description of the Majorana mass matrix with three neutrino masses, three mixing angles and three CP violating phases. In particular, only two independent CP violating sources give rise to three CP violating phases. The efficient and comprehensive method is proposed in this paper to investigate four-zero textures in Type-I seesaw. We numerically show the possible range of CP violating phases in the plane of a Dirac CP violating phase and one of Majorana phases. Some cases show the strong correlations among two phases. These correlations can be explained by hidden relations among the elements of Majorana matrix with the four-zero textures. The hidden relations are classified according to the position of one vanishing off-diagonal element of Majorana mass matrix. The Majorana mass matrix all of whose elements are non-vanishing also produces other hidden relations particularly in the case of four-zero textures. By applying the hidden relations, we describe the concrete correlations among CP violating phases.

  • Zee Model with Flavor Dependent Global $U(1)$ Symmetry
    OU-HET 1013

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

    We study a simple extension of the Zee model, in which a discrete $Z_2$ symmetry imposed in the original model is replaced by a global $U(1)$ symmetry retaining the same particle content. Due to the $U(1)$ symmetry with flavor dependent charge assignments, the lepton sector has an additional source of flavor violating Yukawa interactions with a controllable structure, while the quark sector does not at tree level. We show that current neutrino oscillation data can be explained under constraints from lepton flavor violating decays of charged leptons in a successful charge assignment of the $U(1)$ symmetry. In such scenario, we find a characteristic pattern of lepton flavor violating decays of additional Higgs bosons, which can be a smoking gun signature at collider experiments.

  • Novel Flavon Stabilization with Trimaximal Neutrino Mixing

    by: Chigusa, So (Tokyo U.) et al.

    We construct a supersymmetric $S_4$ flavor symmetry model with one of the trimaximal neutrino mixing patterns, the so-called TM$_1$, by using the novel way to stabilize flavons, which we proposed recently. The flavons are assumed to have tachyonic supersymmetry breaking mass terms and stabilized by higher-dimensional terms in the potential. We can obtain the desired alignment structure of the flavon vacuum expectation values to realize neutrino masses and mixings consistent with the current observations. This mechanism naturally avoids the appearance of dangerous cosmological domain walls.

  • Thermalisation of sterile neutrinos in the early Universe in the 3+1 scheme with full mixing matrix

    by: Gariazzo, S. (U. Valencia (main)) et al.

    In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full $4\times4$ mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, $N_{\rm eff}$, and its dependence on the three additional mixing angles ($\theta_{14}$, $\theta_{24}$, $\theta_{34}$) and on the squared mass difference $\Delta m^2_{41}$ is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised ($N_{\rm eff}\simeq 4$).

  • Scalar neutrino dark matter in $U(1)_X$SSM

    by: Zhao, Shu-Min (Hebei U.) et al.

    $U(1)_X$SSM is the extension of the minimal supersymmetric standard model(MSSM) and its local gauge group is $SU(3)_C\times SU(2)_L \times U(1)_Y \times U(1)_X$. Compared with MSSM, it has three singlet new Higgs superfields and right handed neutrinos. In the framework of $U(1)_X$SSM, we study the Higgs mass and suppose the lightest CP-even sneutrino as cold dark matter candidate. For the lightest CP-even sneutrino, the relic density and the cross section with nucleon are both researched. In our chosen parameter space, the numerical results show that considering the lightest CP-even sneutrino as cold dark matter the obtained results satisfy the constraints from the relic density and the scattering off nucleon.

  • The 2-Neutrino Exchange Potential with Mixing: A Probe of Neutrino Physics and CP Violation

    by: Krause, D.E. (Wabash Coll.) et al.

    The 2-neutrino exchange potential is a Standard Model weak potential arising from the exchange of virtual neutrino-antineutrino pairs which must include all neutrino properties, including the number of flavors, their masses, fermionic nature (Dirac or Majorana), and CP violation. We describe a new approach for calculating the spin-independent 2-neutrino exchange potential, including the mixing of three neutrino mass states and CP violation.

  • Probes of the Standard Model effective field theory extended with a right-handed neutrino

    by: Alcaide, Julien (Valencia U.) et al.

    If neutrinos are Dirac particles and, as suggested by the so far null LHC results, any new physics lies at energies well above the electroweak scale, the Standard Model effective field theory has to be extended with operators involving the right-handed neutrinos. In this paper, we study this effective field theory and set constraints on the different dimension-six interactions. To that aim, we use LHC searches for associated production of light (and tau) leptons with missing energy, monojet searches, as well as pion and tau decays. Our bounds are generally above the TeV for order one couplings. One particular exception is given by operators involving top quarks. These provide new signals in top decays not yet studied at colliders. Thus, we also design an LHC analysis to explore these signatures in the $t\overline{t}$ production. Our results are also valid if the right-handed neutrinos are Majorana and long-lived.

  • The Lifetime Frontier: Search for New Physics with Long-Lived Particles

    by: Hung, P.Q. (Virginia U.)

    The search for new physics with long-lived particles is an ongoing and thriving effort in the High Energy Physics community which necessitates new search strategies such as novel algorithms, novel detectors, etc...For these reasons, one could perhaps add another frontier, the Lifetime Frontier, to the standard three (Energy, Intensity and Cosmic). In this talk, I will describe a BSM physics model whose characteristic signatures are decays of new (mirror) fermions at displaced vertices, a domain belonging to the Lifetime Frontier. It is a model of {\em non-sterile} right-handed neutrinos whose masses are proportional to the electroweak scale $\Lambda_{EW} \sim 246 \, GeV$. The model proposed a solution to the strong CP problem with a surprising connection between the sizes of the neutrino masses and the $\theta$-angle which contributes to the neutron electric dipole moment.

  • Long Lived Particles Searches in Heavy Ion Collisions at the LHC

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

    We show that heavy ion collisions at the LHC provide a promising environment to search for new long lived particles. A main advantage lies in the possibility to operate the main detectors with lower triggers, which can increase the number of observable events by orders of magnitude if the long lived particles are produced with low transverse momentum. If the LHC is operated with Pb nuclei this is insufficient to overcome the suppression due to the lower instantaneous luminosity compared to proton runs, but for lighter nuclei a higher sensitivity per running time can be achieved than in proton collisions. We illustrate this explicitly for heavy neutrino searches in the Minimal Neutrino Standard Model. In less minimal models with complicated event topology the absence of pile-up provides another key advantage of heavy ion collisions because it avoids the problem of vertex mis-identification. This provides strong motivation to further explore the possibility to search for New Physics in heavy ion collisions.

  • C$\nu$B detection through angular correlations in inverse $\beta$-decay

    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 $\beta$-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 $\beta$-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 C$\nu$B 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 $\beta$-particles and can be operative even if this resolution exceeds the largest neutrino mass.

  • Constraint on the Solar $\Delta m^2$ from combined Daya Bay & RENO data

    by: Hernandez-Cabezudo, Alvaro (KIT, Karlsruhe) et al.

    There is a well known 2$\sigma$ tension in the measurements of the solar $\Delta m^2$ between KamLAND and SNO/Super-K. Precise determination of the solar $\Delta m^2$ is especially important in connection with current and future long baseline CP violation measurements. Reference~\cite{Seo:2018rrb} points out that currently running short baseline reactor neutrino experiments, Daya Bay and RENO, can also constrain solar $\Delta m^2$ value as demonstrated by a GLoBES simulation with a limited systematic uncertainty consideration. In this work, the publicly available data, from Daya Bay (1,958 days) and RENO (2,200 days) are used to constrain the solar $\Delta m^2$. Verification of our method through $\Delta m^2_{ee}$ and $\sin^2 \theta_{13}$ measurements is discussed in Appendix A. Using this verified method, reasonable constraints on the solar $\Delta m^2$ are obtained using the current publicly available Daya Bay and RENO data, both individually and combined. We find that the combined data of Daya Bay and RENO set an upper limit on the Solar $\Delta m^2$ of 17 $\times 10^{-5}$ eV$^2$ at the 95\% C.L., including both systematic and statistical uncertainties. This constraint is slightly more than twice the KamLAND value. As this combined result is still statistics limited, even though driven by Daya Bay data, the constraint will improve with the additional running of this experiment.

  • Pre-Supernova Neutrinos in Large Dark Matter Direct Detection Experiments

    by: Raj, Nirmal (TRIUMF) et al.

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

  • Wave Packets Losing Their Covariance

    by: Mohammed, Hosam (Beijing, GUCAS) et al.

    In neutrino physics, it is sometimes assumed that all wave packets must transform covariantly as Lorentz vectors. We show in a simple example that even if the initial conditions of a wave packet are covariant, then evolution in a relativistic interacting theory followed by a measurement of entangled particles can lead to a wave packet which is no longer covariant.

  • Sensitivity to neutrino-antineutrino transitions for boron neutrinos
    Nucl.Phys. B944 (2019) 114661

    by: Li, S.J. (Zhongshan U.) et al.

    Neutrino-antineutrino conversion is an important new physics process. The observation of this phenomenon could indicate total lepton number violation and potential CPT-violation. Searching for the appearance of electron antineutrinos from solar neutrinos from $\rm^8B$ decay allows us to hunt for this rare process, although it can also be explained by other mechanisms or hypotheses. This analysis examines the capabilities of observing neutrino-antineutrino transition from $\rm^8B$ unoscillated solar neutrinos using different liquid scintillator detector configurations. High energy reactor neutrinos and atmospheric neutrinos are the two dominant background sources. Large volume liquid scintillator detectors with deep underground shielding, placed far away from reactors and with capabilities of pulse shaped discrimination will significantly increase the search sensitivity. It is demonstrated that for the next generation of large liquid scintillator detectors being planned or under construction, the sensitivity to the average probability of neutrino-antineutrino transitions can reach $10^{-6}$, which is an order of magnitude better than the current best experimental limits.

  • On the Determination of Leptonic CP Violation and Neutrino Mass Ordering in Presence of Non-Standard Interactions: Present Status
    JHEP 1906 (2019) 055

    by: Esteban, Ivan (Barcelona U., ECM) et al.

    We perform a global analysis of neutrino data in the framework of three massive neutrinos with non-standard neutrino interactions which affect their evolution in the matter background. We focus on the effect of NSI in the present observables sensitive to leptonic CP violation and to the mass ordering. We consider complex neutral current neutrino interactions with quarks whose lepton-flavor structure is independent of the quark type. We quantify the status of the "hints" for CP violation, the mass-ordering and non-maximality of $\theta_{23}$ in these scenarios. We also present a parametrization-invariant formalism for leptonic CP violation in presence of a generalized matter potential induced by NSI.

  • Generalized Parton Distributions from charged current meson production
    Phys.Rev. D99 (2019) 116005

    by: Siddikov, Marat (Santa Maria U., Valparaiso) et al.

    In this paper we prove that the simultaneous study of both $\rho$- and $\pi$-meson production by charged currents in Bjorken kinematics allows for a very clean extraction of the leading twist Generalized Parton Distributions of the target, with inherent control of the contribution of higher-twist corrections. Also, it might provide target-independent constraints on the distribution amplitudes of the produced mesons. We expect that such processes might be studied either in neutrino-induced or in electron-induced processes. According to our numerical estimates, the cross-sections of these processes are within the reach of JLab and EIC experiments.

  • Gravitational waves from the minimal gauged $U(1)_{B-L}$ model
    Phys.Rev. D99 (2019) 095039

    by: Hasegawa, Taiki (Hokkaido U.) et al.

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

  • Update on decaying and annihilating heavy dark matter with the 6-year IceCube HESE data
    JCAP 1905 (2019) 051

    by: Bhattacharya, Atri (Liege U.) et al.

    In view of the IceCube's 6-year high-energy starting events (HESE) sample, we revisit the possibility that the updated data may be better explained by a combination of neutrino fluxes from dark matter decay and an isotropic astrophysical power-law than purely by the latter. We find that the combined two-component flux qualitatively improves the fit to the observed data over a purely astrophysical one, and discuss how these updated fits compare against a similar analysis done with the 4-year HESE data. We also update fits involving dark matter decay via multiple channels, without any contribution from the astrophysical flux. We find that a DM-only explanation is not excluded by neutrino data alone. Finally, we also consider the possibility of a signal from dark matter annihilations and perform analogous analyses to the case of decays, commenting on its implications.

  • Reconciling dark matter, $R_{K^{(*)}}$ anomalies and $(g-2)_{\mu}$ in an ${L_{\mu}-L_{\tau}}$ scenario
    JHEP 1905 (2019) 165

    by: Biswas, Anirban (IACS, Kolkata) et al.

    We propose an anomaly free unified scenario by invocation of an extra local ${\rm U(1)}_{L_{\mu}-L_{\tau}}$ gauge symmetry. This scenario simultaneously resolves the $R_{K^{(*)}}$ anomalies, the dark matter puzzle and the long-standing discrepancy in muon's anomalous magnetic moment. A complex scalar ($\eta$) having nonzero ${L_{\mu}-L_{\tau}}$ charge has been introduced to break this new U(1) symmetry spontaneously. Moreover, for the purpose of studying dark matter phenomenology and $R_{K^{(*)}}$ anomalies in a correlated manner, we introduce an inert ${\rm SU(2)}_L$ scalar doublet ($\Phi$), a $\mathbb{Z}_2$-odd real singlet scalar ($S$) and a $\mathbb{Z}_2$-odd coloured fermion ($\chi$) which transforms vectorially under the ${\rm U(1)}_{L_{\mu}-L_{\tau}}$ symmetry. This extra gauge symmetry provides a new gauge boson $Z_{\mu\tau}$ which not only gives additional contribution to both $b\to s \ell\ell$ transition and $(g-2)_{\mu}$ but also provides a crucial annihilation channel for dark matter candidate $\rho_1$ of the present scenario. This $\rho_1$ is an admixture of CP-even neutral component of $\Phi$ and $S$. Our analysis shows that the low mass dark matter regime ($M_{\rho_1}\lesssim 60$ GeV) is still allowed by the experiments like XENON1T, LHC (via Higgs invisible branching) and Fermi-LAT, making the dark matter phenomenology drastically different from the standard Inert Doublet and the Scalar Singlet models. Furthermore, the present model is also fairly consistent with the observed branching ratio of $B\to X_s\gamma$ in $3\sigma$ range and is quite capable of explaining neutrino masses and mixings via Type-I seesaw mechanism if we add three right handed neutrinos in the particle spectrum. Finally, we use the latest ATLAS data of non-observation of a resonant $\ell^+\ell^-$ signal at the 13 TeV LHC to constrain the mass-coupling plane of $Z_{\mu\tau}$.

  • Probing nonstandard lepton number violating interactions in neutrino oscillations
    Phys.Rev. D99 (2019) 115011

    by: Bolton, Patrick D. (University Coll. London) et al.

    We discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_{\nu}/E_{\nu})^{2}$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mass suppression while also factorising the oscillation probability from the total rate. Such interactions arise from dimension-six operators in the low energy effective field theory of the Standard Model. We derive general and simplified expressions for the lepton number violating oscillation probabilities and use limits from MINOS and KamLAND to place bounds on the interaction strength in interplay with the unknown Majorana phases in neutrino mixing. We compare the bounds with those from neutrinoless double beta decay and other microscopic lepton number violating processes and outline the requirements for future short- and long-baseline neutrino oscillation experiments to improve on the existing bounds.

  • Deviations to Tri-Bi-Maximal mixing in the limit of $\mu − \tau$ symmetry
    Phys.Lett. B794 (2019) 89-95

    by: Rivera-Agudelo, Diana C. (Santiago de Cali U.) et al.

    In the limit of an approximate $\mu-\tau$ symmetry in the neutrino mass matrix, we explore deviations to the Tri-Bi-Maximal mixing pattern in the neutrino sector. We consider two different ansatzes for the corrected pattern to predict the current values of neutrino mixing parameters. We show that it is possible to constrain the Majorana $CP$ phases by studying their correlation to the mixing parameters and we study their effects on neutrinoless double beta decay observables. These predictions are sharp for the quasi-degenerate ordering and can be tested in upcoming experiments.

  • A model-independent approach to the reconstruction of multi-flavor supernova neutrino energy spectra
    Phys.Rev. D99 (2019) 123009

    by: Li, Hui-Ling (Beijing, Inst. High Energy Phys.) et al.

    The model-independent reconstruction of the energy spectra of $\overline{\nu}^{}_e$, $\nu^{}_e$ and $\nu^{}_x$ (i.e., $\nu^{}_\mu$, $\nu^{}_\tau$ and their antiparticles) from the future observation of a galactic core-collapse supernova (SN) is of crucial importance to understand the microscopic physics of SN explosions. To this end, we propose a practically useful method to combine the multi-channel detection of SN neutrinos in a large liquid-scintillator detector (e.g., JUNO), namely, the inverse beta decay $\overline{\nu}^{}_e + p \to e^+ + n$, the elastic neutrino-proton scattering $\nu + p \to \nu + p$ and the elastic neutrino-electron scattering $\nu + e^- \to \nu + e^-$, and reconstruct the energy spectra of $\overline{\nu}^{}_e$, $\nu^{}_e$ and $\nu^{}_x$ by making the best use of the observational data in those three channels. In addition, the neutrino energy spectra from the numerical simulations of the delayed neutrino-driven SN explosions are implemented to demonstrate the robustness of our method. Taking the ordinary matter effects into account, we also show how to extract the initial neutrino energy spectra in the presence of neutrino flavor conversions.

  • New Weinberg operator for neutrino mass and its seesaw origin
    JHEP 1905 (2019) 169

    by: Hernandez-Garcia, Josu (INFN, Trieste) et al.

    We consider a new Weinberg operator for neutrino mass of the form $H_u\tilde{H_d}L_iL_j$ involving two different Higgs doublets $H_u, H_d$ with opposite hypercharge, where $\tilde{H_d}$ is the charge conjugated doublet. It may arise from a model where the two Higgs doublets carry the same charge under a $U(1)'$ gauge group which forbids the usual Weinberg operator but allows the mixed one. The new Weinberg operator may be generated via two right-handed neutrinos oppositely charged under the $U(1)'$, which may be identified as components of a fourth vector-like family in a complete model. Such a version of the type I seesaw model, which we refer to as type Ib to distinguish it from the usual type Ia seesaw mechanism which yields the usual Weinberg operator, allows the possibility of having potentially large violations of unitarity of the leptonic mixing matrix whose bounds we explore. We also consider the relaxation of the unitarity bounds due to the further addition of a single right-handed neutrino, neutral under $U(1)'$, yielding a usual type Ia seesaw contribution.

  • Doubly-charged Higgs Boson at Future Electron-Proton Collider
    Phys.Rev. D99 (2019) 115015

    by: Dev, P.S. Bhupal (McDonnell Ctr. Space Sci.) et al.

    We explore the discovery prospect of the doubly-charged component of an $SU(2)_L$-triplet scalar at the future $e^- p$ collider FCC-eh, proposed to operate with an electron beam energy of 60 GeV and a proton beam energy of 50 TeV. We consider the associated production of the doubly-charged Higgs boson along with leptons and jet(s), and its subsequent prompt decay to same-sign lepton pair. This occurs for ${\cal O}(1)$ Yukawa coupling of the scalar triplet with charged leptons, which is expected for reasonably small vacuum expectation values of the neutral component of the triplet field that governs the neutrino mass generation in the type-II seesaw. We present our analysis for two different final states, $3l+\ge1j$ and an inclusive $\ge2l+\ge1j$ channel. Considering its decay to electrons only, we find that the doubly-charged Higgs with mass around a TeV could be observed at $3\sigma$ confidence level with $\mathcal{O}(200)\, \rm{fb}^{-1}$ of integrated luminosity, while masses up to 2 TeV could be probed within a few years of data accumulation. The signal proposed here becomes essentially background-free, if it is triggered in the $\mu\mu$ mode and a $5\sigma$ discovery is achievable in this channel for a TeV-scale doubly-charged Higgs with an integrated luminosity as low as $\mathcal{O} (50)\, \rm{fb}^{-1}$. We also highlight the sensitivity of FCC-eh to the Yukawa coupling responsible for production of the doubly-charged Higgs boson as a function of its mass in both the $ee$ and $\mu\mu$ channels.

  • On the Origin of Two-Loop Neutrino Mass from SU(5) Grand Unification
    Phys.Rev. D99 (2019) 115016

    by: Saad, Shaikh (Oklahoma State U.)

    In this work we propose a renormalizable model based on the SU(5) gauge group where neutrino mass originates at the two-loop level without extending the fermionic content of the Standard Model (SM). Unlike the conventional SU(5) models, in this proposed scenario, neutrino mass is intertwined with the charged fermion masses. In addition to correctly reproducing the SM charged fermion masses and mixings, neutrino mass is generated at the quantum level, hence naturally explains the smallness of neutrino masses. In this setup, we provide examples of gauge coupling unification that simultaneously satisfy the proton decay constraints. This model has the potential to be tested experimentally by measuring the proton decay in the future experiments. Scalar leptoquarks that are naturally contained within this framework can accommodate the recent B-physics anomalies.

  • The flavor composition of astrophysical neutrinos after 8 years of IceCube: an indication of neutron decay scenario?
    Eur.Phys.J. C79 (2019) 500

    by: Palladino, Andrea (DESY)

    In this work we present an updated study of the flavor composition suggested by astrophysical neutrinos observed by IceCube. The main novelties compared to previous studies are the following: 1) we use the most recent measurements, namely 8 years of throughgoing muons and 7.5 years of High Energy Starting Events (HESE); 2) we consider a broken power law spectrum, in order to be consistent with the observations between 30 TeV and few PeV; 3) we use the throughgoing muon flux to predict the number of astrophysical HESE tracks. We show that accounting for the three previous elements, the result favors surprisingly the hypothesis of neutrinos produced by neutron decay, disfavoring the standard picture of neutrinos from pion decay at 2.0$\sigma$ and the damped muons regime at $2.6 \sigma$, once the atmospheric background is considered. Although the conventional scenario is not yet completely ruled out in the statistically and alternative interpretations are also plausible, such as an energy spectrum characterized by a non trivial shape, this intriguing result may suggest new directions for both theoretical interpretation and experimental search strategies.

  • Making dark matter out of light: freeze-in from plasma effects
    Phys.Rev. D99 (2019) 115009

    by: Dvorkin, Cora (Harvard U.) et al.

    Dark matter (DM) could couple to particles in the Standard Model (SM) through a light vector mediator. In the limit of small coupling, this portal could be responsible for producing the observed DM abundance through a mechanism known as freeze-in. Furthermore, the requisite DM-SM couplings provide a concrete benchmark for direct and indirect searches for DM. In this paper, we present updated calculations of the relic abundance for DM produced by freeze-in through a light vector mediator. We identify an additional production channel: the decay of photons that acquire an in-medium plasma mass. These plasmon decays are a dominant channel for DM production for sub-MeV DM masses, and including this channel leads to a significant reduction in the predicted signal strength for DM searches. Accounting for production from both plasmon decays and annihilations of SM fermions, the DM acquires a highly non-thermal phase space distribution which impacts the cosmology at later times; these cosmological effects will be explored in a companion paper.

  • Simplest Radiative Dirac Neutrino Mass Models
    Nucl.Phys. B943 (2019) 114636

    by: Saad, Shaikh (Oklahoma State U.)

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

  • Revisiting the LHC reach in the displaced region of the minimal left-right symmetric model
    Phys.Rev. D99 (2019) 115013

    by: Cottin, Giovanna (Taiwan, Natl. Taiwan U.) et al.

    We revisit discovery prospects for a long-lived sterile neutrino $N$ at the Large Hadron Collider (LHC) in the context of left-right symmetric theories. We focus on a displaced vertex search strategy sensitive to $\mathcal{O}$(GeV) neutrino masses produced via a right-handed $W_{R}$ boson. Both on-shell and off-shell Drell-Yan production of $W_{R}$ are considered. We estimate the reach as a function of $m_{N}$ and $m_{W_{R}}$. With $\sqrt{s}=13$ TeV and 300/fb of integrated luminosity, the LHC can probe neutrino masses as high as $\sim 30$ GeV and $m_{W_{R}}$ around 6 TeV. The reach goes up to 11.5 TeV with 3000/fb and $m_{N}\sim 45$ GeV. This represents an improvement of a factor of 2 in sensitivity with respect to earlier work.

  • Entangled Neutrino States in a Toy Model QFT
    Eur.Phys.J. C79 (2019) 491

    by: Evslin, Jarah (Lanzhou, Inst. Modern Phys.) et al.

    It has been claimed that wave packets must be covariant and also that decohered neutrino oscillations are always revived during measurement. These conjectures are supported by general arguments which are not specific to the electroweak theory, and so if they are true for neutrinos they will also be true for simplified models. In this paper we produce such a simplified model in which the neutrino wave function, including its entanglement with the source particle and the environment, can be calculated explicitly in quantum field theory. It exhibits neutrino oscillation, which is reduced at late times by decoherence due to interactions of the source with the environment. One simple lesson from this model is that only the difference between the environmental interactions before and after neutrino emission can reduce the amplitude of neutrino oscillations. The model will be used to test the conjectures in a companion paper.

  • Enhancing the hierarchy and octant sensitivity of ESS$\nu$SB in conjunction with T2K, NO$\nu$A and ICAL@INO
    JHEP 1905 (2019) 137

    by: Chakraborty, Kaustav (Ahmedabad, Phys. Res. Lab) et al.

    The main aim of the ESS$\nu$SB proposal is the discovery of the leptonic CP phase $\delta_{CP}$ with a high significance ($5\sigma$ for 50% values of $\delta_{CP}$) by utilizing the physics at the second oscillation maxima of the $P_{\mu e}$ channel. It can achieve $3\sigma$ sensitivity to hierarchy for all values of $\delta_{CP}$. In this work, we concentrate on the hierarchy and octant sensitivity of the ESS$\nu$SB experiment. We show that combining the ESS$\nu$SB experiment with the atmospheric neutrino data from the proposed India-based Neutrino Observatory(INO) experiment can result in an increased sensitivity to mass hierarchy. In addition, we also combine the results from the ongoing experiments T2K and NO$\nu$A assuming their full runtime and present the combined sensitivity of ESS$\nu$SB + ICAL@INO + T2K + NO$\nu$A. We show that while by itself ESS$\nu$SB can have up to $3\sigma$ hierarchy sensitivity, the combination of all the experiments can give up to $5\sigma$ sensitivity depending on the true hierarchy-octant combination. The octant sensitivity of ESS$\nu$SB is low by itself. However the combined sensitivity of all the above experiments can give up to $3\sigma$ sensitivity depending on the choice of true hierarchy and octant. We discuss the various degeneracies and the synergies that lead to the enhanced sensitivity when combining different experimental data.

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

    by: Ma, Ernest (UC, Riverside)

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

  • Littlest mu-tau seesaw
    JHEP 1905 (2019) 217

    by: King, Stephen F. (Southampton U.) et al.

    We propose a $\mu-\tau$ reflection symmetric Littlest Seesaw ($\mu\tau$-LSS) model. In this model the two mass parameters of the LSS model are fixed to be in a special ratio by symmetry, so that the resulting neutrino mass matrix in the flavour basis (after the seesaw mechanism has been applied) satisfies $\mu-\tau$ reflection symmetry and has only one free adjustable parameter, namely an overall free mass scale. However the physical low energy predictions of the neutrino masses and lepton mixing angles and CP phases are subject to renormalisation group (RG) corrections, which introduces further parameters. Although the high energy model is rather complicated, involving $(S_4\times U(1))^2$ and supersymmetry, with many flavons and driving fields, the low energy neutrino mass matrix has ultimate simplicity.

  • Spin-Independent Two-Neutrino Exchange Potential with Mixing and $CP$-Violation
    Phys.Rev. D99 (2019) 116006

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

    We develop a new approach for calculating the spin-independent 2-neutrino exchange potential (2-NEP) between non-relativistic fermions which places emphasis on the neutrino vacuum state, an area of theoretical interest in recent years. The 2-NEP is a natural probe of fundamental issues of neutrino physics such as neutrino masses, flavor mixing, the number of neutrino flavors, neutrino nature (Dirac or Majorana), $CP$-violation, and the neutrino vacuum state. We explore the dependence of the 2-NEP on the mixing of neutrino mass states assuming normal and inverted mass ordering for nucleon-nucleon, nucleon-lepton, and lepton-lepton interactions, and the $CP$-violation phase in the neutrino mixing matrix.

  • Reactor neutrino oscillations as constraints on Effective Field Theory
    LPT Orsay 19-02
    CERN-TH-2019-002 LPT Orsay 19-02
    JHEP 1905 (2019) 173

    by: Falkowski, Adam (Orsay, LPT) et al.

    We study constraints on the Standard Model Effective Field Theory (SMEFT) from neutrino oscillations in short-baseline reactor experiments. We calculate the survival probability of reactor antineutrinos at the leading order in the SMEFT expansion, that is including linear effects of dimension-6 operators. It is shown that, at this order, reactor experiments alone cannot probe charged-current contact interactions between leptons and quarks that are of the (pseudo)vector (V±A) or pseudo-scalar type. We also note that flavor-diagonal (pseudo)vector coefficients do not have observable effects in oscillation experiments. In this we reach novel or different conclusions than prior analyses of non-standard neutrino interactions. On the other hand, reactor experiments offer a unique opportunity to probe tensor and scalar SMEFT operators that are off-diagonal in the lepton-flavor space. We derive constraints on the corresponding SMEFT parameters using the most recent data from the Daya Bay and RENO experiments.

  • Lepton Flavor Violation and Neutrino Masses from $A_5$ and CP in the Non-Universal MSSM
    JHEP 1906 (2019) 047

    by: López-Ibáñez, M.L. (Rome III U.) et al.

    We analyze the phenomenological consequences of embedding a flavor symmetry based on the groups $A_5$ and CP in a supersymmetric framework. We concentrate on the leptonic sector, where two different residual symmetries are assumed to be conserved at LO for charged and neutral leptons. All possible realizations to generate neutrino masses at tree level are investigated. Sizable flavor violating effects in the charged lepton sector are unavoidable due to the non-universality of soft-breaking terms determined by the symmetry. We derive testable predictions for the neutrino spectrum, lepton mixing and flavor changing processes with non-trivial relations among observables.

  • New sensitivity goal for neutrinoless double beta decay experiments
    Phys.Rev. D99 (2019) 095038

    by: Vishnudath, K.N. (Ahmedabad, Phys. Res. Lab) et al.

    We study the implications of the Dark-LMA (DLMA) solution to the solar neutrino problem for neutrinoless double beta decay (0νββ). We show that, while the predictions for the effective mass governing 0νββ remain unchanged for the inverted mass scheme, that for normal ordering becomes higher for the DLMA parameter space and moves into the “desert region” between the two. This sets a new goal for the sensitivity reach for the next-generation experiments if no signal is found for the inverted ordering by the future search programs.

  • Sequentially loop-generated quark and lepton mass hierarchies in an extended Inert Higgs Doublet model
    JHEP 1906 (2019) 056

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

    Extended scalar and fermion sectors offer new opportunities for generating the observed strong hierarchies in the fermion mass and mixing patterns of the Standard Model (SM). In this work, we elaborate on the prospects of a particular extension of the Inert Higgs doublet model where the SM hierarchies are generated sequentially by radiative virtual corrections in a fully renormalisable way, i.e. without adding any non-renormalisable Yukawa terms or soft-breaking operators to the scalar potential. Our model has a potential to explain the recently observed $R_{K}$ and $R_{K^{\ast }}$ anomalies, thanks to the non universal $U_{1X}$ assignments of the fermionic fields that yield non universal $Z^{\prime}$ couplings to fermions. We explicitly demonstrate the power of this model for generating the realistic quark, lepton and neutrino mass spectra. In particular, we show that due to the presence of both continuous and discrete family symmetries in the considered framework, the top quark acquires a tree-level mass, lighter quarks and leptons get their masses at one- and two-loop order, while neutrino masses are generated at three-loop level. The minimal field content, particle spectra and scalar potential of this model are discussed in detail.

  • Neutral-current weak pion production off the nucleon in covariant chiral perturbation theory
    Phys.Lett. B794 (2019) 109-113

    by: Yao, De-Liang (Lanzhou, Inst. Modern Phys.) et al.

    Neutral current single pion production induced by neutrinos and antineutrinos on nucleon targets has been investigated in manifestly relativistic baryon chiral perturbation theory with explicit $\Delta(1232)$ degrees of freedom up to $\mathcal{O}(p^3)$. At low energies, where chiral perturbation theory is applicable, the total cross sections for the different reaction channels exhibit a sizable non-resonant contribution, which is not present in event generators of broad use in neutrino oscillation and cross section experiments such as GENIE and NuWro.

  • Low-scale Leptogenesis with Minimal Lepton Flavour Violation
    Phys.Rev. D99 (2019) 123508

    by: Dolan, Matthew J. (ARC, CoEPP, Melbourne) et al.

    We analyse the feasibility of low-scale leptogenesis where the inverse seesaw (ISS) and linear seesaw (LSS) terms are not simultaneously present. In order to generate the necessary mass splittings, we adopt a Minimal Lepton Flavour Violation (MLFV) hypothesis where a sterile neutrino mass degeneracy is broken by flavour effects. We find that resonant leptogenesis is feasible in both scenarios. However, because of a flavour alignment issue, MLFV-ISS leptogenesis succeeds only with a highly tuned choice of Majorana masses. For MLFV-LSS, on the other hand, a large portion of parameter space is able to generate sufficient asymmetry. In both scenarios we find that the lightest neutrino mass must be of order $10^{-2}\text{ eV}$ or below for successful leptogenesis. We briefly explore implications for low-energy flavour violation experiments, in particular $\mu \rightarrow e\,\gamma$. We find that the future MEG-II experiment, while sensitive to MLFV in our setup, will not be sensitive to the specific regions required for resonant leptogenesis.

  • Peccei-Quinn Symmetry and Nucleon Decay in Renormalizable SUSY $SO$(10)
    JHEP 1906 (2019) 045

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

    We suggest simple ways of implementing Peccei-Quinn (PQ) symmetry to solve the strong CP problem in renormalizable SUSY SO(10) models with a minimal Yukawa sector. Realistic fermion mass generation requires that a second pair of Higgs doublets survive down to the PQ scale. We show how unification of gauge couplings can be achieved in this context. Higgsino mediated proton decay rate is strongly suppressed by a factor of (M$_{PQ}$/M$_{GUT}$)$^{2}$, which enables all SUSY particles to have masses of order TeV. With TeV scale SUSY spectrum, $ p\to \overline{v}{K}^{+} $ decay rate is expected to be in the observable range. Lepton flavor violating processes μ → eγ decay and μ − e conversion in nuclei, induced by the Dirac neutrino Yukawa couplings, are found to be within reach of forthcoming experiments.

  • Trimaximal Neutrino Mixing from Modular A4 Invariance with Residual Symmetries
    SISSA 57/2018/FISI
    Phys.Lett. B793 (2019) 247-258

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

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

  • Safe Trinification
    CP3-Origins-2018-47 DNRF90
    Phys.Rev. D99 (2019) 115017

    by: Wang, Zhi-Wei (Waterloo U.) et al.

    In this work, we provide a UV safe Trinification theory in which the Standard Model is embedded. Using recently developed large number-of-flavor techniques, safety is achieved by adding to the theory gauged vector-like fermions. We find that all gauge, scalar quartic, and Yukawa couplings achieve an interacting ultraviolet fixed point below the Planck scale. We find renormalization group flow solutions matching the Standard Model in the IR, indicating a truly UV completion of the Standard Model. Imposing constraints that realistic Higgs, top, bottom, tau and reasonable neutrino masses are recovered, we find the set of allowed solutions to be quite restrictive. Furthermore, the symmetry breaking scale is predicted to be around 10 TeV, making this model vulnerable to experiment.

  • Finite modular subgroups for fermion mass matrices and baryon/lepton number violation
    Phys.Lett. B794 (2019) 114-121

    by: Kobayashi, Tatsuo (Hokkaido U.) et al.

    We study a flavor model that the quark sector has the $S_3$ modular symmetry,while the lepton sector has the $A_4$ modular symmetry. Our model leads to characteristic quark mass matrices which are consistent with experimental data of quark masses, mixing angles and the CP violating phase. The lepton sector is also consistent with the experimental data of neutrino oscillations. We also study baryon and lepton number violations in our flavor model.

  • Heavy Neutrinos with Dynamic Jet Vetoes: Multilepton Searches at $\sqrt{s} = 14,~27,$ and $100$ TeV
    JHEP 1906 (2019) 049

    by: Pascoli, Silvia (Durham U., IPPP) et al.

    Heavy neutrinos $(N)$ remain one of most promising explanations for the origin of neutrinos' tiny masses and large mixing angles. In light of broad advances in understanding and modeling of hadron collisions at large momentum transfers, we revisit the long-standard search strategy for heavy $N$ decaying to multiple charged leptons $(\ell)$, $pp \to N\ell X \to 3\ell \nu X$. For electroweak and TeV-scale $N$, we propose a qualitatively new collider analysis premised on a dynamic jet veto and discriminating, on an event-by-event basis, according to the relative amount of hadronic and leptonic activity. We report that the sensitivity to heavy neutrinos at the CERN Large Hadron Collider (LHC) can be improved by roughly an order of magnitude over the collider's lifetime. At $\sqrt{s}=14$ TeV with $\mathcal{L}=3~{\rm ab}^{-1}$, we find active-sterile mixing as small as $\vert V_{\ell N}\vert^2 = 10^{-2} ~(10^{-3})$ can be probed for heavy Dirac neutrinos masses $m_N \lesssim 1200~(300)$ GeV. The improvement holds also for Majorana $N$ and is largely independent of whether charged lepton flavor is conserved or violated. The analysis, built almost exclusively from inclusive, transverse observables, is designed to be robust across increasing collider energies, and hence serves as a basis for searches at future colliders: With $\mathcal{L}=15~{\rm ab}^{-1}$ at $\sqrt{s}=27$ TeV, one can probe mixing below $\vert V_{\ell N}\vert^2 = 10^{-2} ~(10^{-3})$ for $m_N \lesssim 3500~(700)$ GeV. At a hypothetical 100 TeV $pp$ collider with $\mathcal{L}=30~{\rm ab}^{-1}$, one can probe mixing below $10^{-4}$ for $m_N \lesssim 200$ GeV, below $10^{-3}$ for $m_N \lesssim 4$ TeV, and below $10^{-2}$ for $m_N \lesssim 15$ TeV. We anticipate these results can be further improved with detector-specific tuning and application of multi-variant / machines learning techniques.

  • Scalar Non-Standard Interactions in Neutrino Oscillation
    Phys.Rev.Lett. 122 (2019) 211801

    by: Ge, Shao-Feng (Tokyo U., IPMU) et al.

    The scalar nonstandard interactions (NSI) can also introduce matter effect for neutrino oscillation in a medium. Especially the recent Borexino data prefer nonzero scalar NSI, ηee=-0.16. In contrast to the conventional vector NSI, the scalar type contributes as a correction to the neutrino mass matrix rather than the matter potential. Consequently, the scalar matter effect is energy independent while the vector one scales linearly with neutrino energy. This leads to significantly different phenomenological consequences in reactor, solar, atmospheric, and accelerator neutrino oscillations. A synergy of different types of experiments, especially those with matter density variation, is necessary to identify the scalar NSI and guarantee the measurement of CP violation at accelerator experiments.

  • Common origin of baryon asymmetry, dark matter and neutrino mass
    JHEP 1905 (2019) 193

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

    In this work, we explain three beyond standard model (BSM) phenomena, namely neutrino masses, the baryon asymmetry of the Universe and Dark Matter, within a single model and in each explanation the right handed (RH) neutrinos play the prime role. Indeed by just introducing two RH neutrinos we can generate the neutrino masses by the Type-I seesaw mechanism. The baryon asymmetry of the Universe can arise from thermal leptogenesis from the decay of lightest RH neutrino before the decoupling of the electroweak sphaleron transitions, which redistribute the B − L number into a baryon number. At the same time, the decay of the RH neutrino can produce the Dark Matter (DM) as an asymmetric Dark Matter component. The source of CP violation in the two sectors is exactly the same, related to the complex couplings of the neutrinos. By determining the comoving number density for different values of the CP violation in the DM sector, we obtain a particular value of the DM mass after satisfying the relic density bound. We also give prediction for the DM direct detection (DD) in the near future by different ongoing DD experiments.

  • Geoneutrinos in Large Direct Detection Experiments
    Phys.Rev. D99 (2019) 093009

    by: Gelmini, Graciela B. (UCLA) et al.

    Geoneutrinos can provide a unique insight into Earth’s interior, its central engine, and its formation history. We study the detection of geoneutrinos in large direct detection experiments, which has been considered nonfeasible. We compute the geoneutrino-induced electron and nuclear recoil spectra in different materials, under several optimistic assumptions. We identify germanium as the most promising target element due to the low nuclear recoil energy threshold that could be achieved. The minimum exposure required for detection would be O(10) ton-years. The realistic low thresholds achievable in germanium and silicon permit the detection of K40 geoneutrinos. These are particularly important to determining Earth’s formation history, but they are below the kinematic threshold of inverse beta decay, the detection process used in scintillator-based experiments.

  • Effective approach to lepton observables: the seesaw case
    Phys.Rev. D99 (2019) 095040

    by: Coy, Rupert (U. Montpellier, L2C) et al.

    In the absence of direct evidence of new physics, any ultraviolet theory can be reduced to its specific set of low-energy effective operators. As a case study, we derive the effective field theory for the seesaw extension of the Standard Model, with sterile neutrinos of mass M>mW. We systematically compute all Wilson coefficients generated at one loop. Hence, it becomes straightforward to (i) identify the seesaw parameters compatible with the smallness of neutrino masses, (ii) compute precision lepton observables, which may be sensitive to scales as large as M∼103  TeV, and (iii) establish sharp correlations among those observables. We find that the flavor-conserving Wilson coefficients set an upper bound on the flavor-violating ones. The low-energy limits on μ→e and τ→e,μ transitions suppress flavor violation in Z and Higgs decays, as well as electric dipole moments, far beyond the experimental reach. The precision measurements of GF, mW, and Z partial decay widths set more stringent bounds than present and future limits on τ→e,μ transitions. We also present a general spurion analysis, to compare the seesaw with different models, thus assessing the discriminating potential of the effective approach.

  • Neutrino flavor as a test of the explosion mechanism of core-collapse supernovae
    Phys.Rev. D99 (2019) 123004

    by: Bar, Nitsan (Weizmann Inst.) et al.

    We study the ratio of neutrino-proton elastic scattering to inverse beta decay event counts, measurable in a scintillation detector like JUNO, as a key observable for identifying the explosion mechanism of a galactic core-collapse supernova. If the supernova is not powered by the core but rather, e.g., by collapse-induced thermonuclear explosion, then a prolonged period of accretion-dominated neutrino luminosity is predicted. Using 1D numerical simulations, we show that the distinct resulting flavor composition of the neutrino burst can be tested in JUNO with high significance, overcoming theoretical uncertainties in the progenitor star profile and equation of state.

  • LHC constraints on a $B−L$ gauge model using Contur
    JHEP 1905 (2019) 154

    by: Amrith, S. (University Coll. London) et al.

    The large and growing library of measurements from the Large Hadron Collider has significant power to constrain extensions of the Standard Model. We consider such constraints on a well-motivated model involving a gauged and spontaneously-broken B − L symmetry, within the Contur framework. The model contains an extra Higgs boson, a gauge boson, and right-handed neutrinos with Majorana masses. This new particle content implies a varied phenomenology highly dependent on the parameters of the model, very well-suited to a general study of this kind. We find that existing LHC measurements significantly constrain the model in interesting regions of parameter space. Other regions remain open, some of which are within reach of future LHC data.

  • Heavy Majorana Neutrino Production at Future $ep$ Colliders
    Phys.Lett. B795 (2019) 49-55

    by: Li, Shi-Yuan (Shandong U.) et al.

    The heavy singlet Majorana neutrinos are introduced to generate the neutrino mass in the so-called phenomenological type-I seesaw mechanism. The phenomena induced by the heavy Majorana neutrinos are important to search for new physics. In this paper, we explore the heavy Majorana neutrino production and decay at future e−p colliders. The corresponding cross sections via W and photon fusion are predicted for different collider energies. Combined with the results of the heavy Majorana neutrino production via single W exchange, this work can provide helpful information to search for heavy Majorana neutrinos at future e−p colliders.

  • Electroweak Baryogenesis From Dark CP Violation
    Phys.Rev.Lett. 122 (2019) 201802

    by: Carena, Marcela (Fermilab) et al.

    We present a novel mechanism of electroweak baryogenesis where CP violation occurs in a dark sector, comprised of standard model gauge singlets, thereby evading the strong electric dipole moment constraints. In this framework, the background of the timelike component of a new gauge boson Zμ′, generated at electroweak temperatures, drives the electroweak sphaleron processes to create the required baryon asymmetry. We first discuss the crucial ingredients for this mechanism to work, and then show that all of them can be elegantly embedded in ultraviolet completions with a spontaneously broken gauged lepton number. The models under consideration have a rich phenomenology and can be experimentally probed in leptophilic Z′ searches, dark matter searches, heavy Majorana neutrino searches, as well as through hunting for new Higgs portal scalars in multilepton channels at colliders.

  • Developing the MeV potential of DUNE: Detailed considerations of muon-induced spallation and other backgrounds
    Phys.Rev. C99 (2019) 055810

    by: Zhu, Guanying (Ohio State U., CCAPP) et al.

    The Deep Underground Neutrino Experiment (DUNE) could be revolutionary for MeV neutrino astrophysics, because of its huge detector volume, unique event reconstruction capabilities, and excellent sensitivity to the νe flavor. However, its backgrounds are not yet known. A major background is expected due to muon spallation of argon, which produces unstable isotopes that later β decay. We present the first comprehensive study of MeV spallation backgrounds in argon, detailing isotope production mechanisms and decay properties, analyzing β energy and time distributions, and proposing experimental cuts. We show that above a nominal detection threshold of 5-MeV electron energy, the most important backgrounds are—surprisingly—due to low-A isotopes, such as Li, Be, and B, even though high-A isotopes near argon are abundantly produced. We show that spallation backgrounds can be powerfully rejected by simple cuts, with clear paths for improvements. We compare these background rates to rates of possible MeV astrophysical neutrino signals in DUNE, including solar neutrinos (detailed in a companion paper [Capozzi et al. arXiv:1808.08232 [hep-ph]], supernova burst neutrinos, and the diffuse supernova neutrino background. Further, to aid trigger strategies, in the Appendixes we quantify the rates of single and multiple MeV events due to spallation, radiogenic neutron capture, and other backgrounds, including through pileup. Our overall conclusion is that DUNE has high potential for MeV neutrino astrophysics, but reaching this potential requires new experimental initiatives.

  • Decays of Long-Lived Relics and Their Signatures at IceCube
    JHEP 1905 (2019) 145

    by: Berghaus, Kim V. (Johns Hopkins U.) et al.

    We consider long-lived relic particles as the source of the PeV-scale neutrinos detected at the IceCube observatory over the last six years. We derive the present day neutrino flux, including primary neutrinos from direct decays, secondary neutrinos from electroweak showering, and tertiary neutrinos from re-scatters off the relic neutrino background. We compare the high-energy neutrino flux prediction to the most recently available datasets and find qualitative differences to expected spectra from other astrophysical processes. We utilize electroweak corrections to constrain heavy decaying relic abundances, using measurements impacted by electromagnetic energy injection, such as light element abundances during Big Bang nucleosynthesis, cosmic microwave background anisotropies, and diffuse $\gamma$-ray spectra. We compare these abundances to those necessary to source the IceCube neutrinos and find two viable regions in parameter space, ultimately testable by future neutrino, $\gamma$-ray, and cosmic microwave background observatories.

  • Left-handed color-sextet diquark in the Kaon system
    Phys.Rev. D99 (2019) 115006

    by: Chen, Chuan-Hung (Taiwan, Natl. Cheng Kung U.) et al.

    We investigate whether a color-sextet scalar diquark (H6) coupling to the left-handed quarks contributes to the ΔS=2 process. It is found that the box diagrams mediated by W and H6 bosons have no contributions to ΔS=2 when the limit of mt=0 is used, and the flavor mixing matrices for diagonalizing quark mass matrices are introduced at the same time. When the heavy top-quark mass effects are taken into account, it is found that in addition to the W-H6 box diagrams significantly contributing to ΔS=2, their effects can be as large as those from the H6-H6 box diagrams. Using the parameters that are constrained by the K0-K¯0 mixing parameter ΔMK and the kaon indirect CP violation εK, we find that the left-handed color-sextet diquark can lead to the kaon direct CP violation being Re(ε′/ε)∼0.3×10-3. In the chosen scheme, although the diquark contribution to KL→π0νν¯ is small, the branching ratio of K+→π+νν¯ can reach the current experimental upper bound.

  • From $D_{s}^{\pm}$ production asymmetry at the LHC to prompt $\nu_{\tau}$ at IceCube
    Phys.Lett. B (2019)

    by: Goncalves, Victor P.
    The description of the heavy meson production at large energies and forward rapidities at the LHC is fundamental to derive realistic predictions of the prompt atmospheric neutrino flux at the IceCube Observatory. In particular, the prompt tau neutrino flux is determined by the decay of $D_s$ mesons produced in cosmic ray - air interactions at high energies and large values of the Feynman - $x_F$ variable. Recent data from the LHCb Collaboration indicate a production asymmetry for $D_s^+$ and $D_s^-$ mesons, which cannot be explained in terms of the standard modelling of the hadronization process. In this paper we demonstrate that this asymmetry can be described assuming an asymmetric strange sea ($s(x) \ne \bar s(x)$) in the proton wave function and taking into account of the charm and strange fragmentation into $D_s$ mesons. Moreover, we show that the strange quark fragmentation contribution is dominant at large - $x_F$ ($\ge 0.3$). The prompt $\nu_{\tau}$ flux is calculated and the enhancement associated to the strange quark fragmentation contribution, disregarded in previous calculations, is estimated.

  • Cosmogenic Neutrinos Through the GRAND Lens Unveil the Nature of Cosmic Accelerators
    JCAP 1905 (2019) 047

    by: Møller, Klaes (Bohr Inst.) et al.

    The sources of cosmic rays with energies above 55 EeV are still mysterious. A guaranteed associated flux of ultra high energy neutrinos known as the cosmogenic neutrino flux will be measured by next generation radio facilities, such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using the orthogonal information provided by the cosmogenic neutrino flux, we here determine the prospects of GRAND to constrain the source redshift evolution and the chemical composition of the cosmic ray sources. If the redshift evolution is known, independently on GRAND's energy resolution, GRAND with 200,000 antennas will constrain the proton/iron fraction to the $\sim5-10\%$ level after one year of data taking; on the other hand, if hints on the average source composition are given, GRAND will measure the redshift evolution of the sources to a $\sim 10\%$ uncertainty. However, the foreseen configuration of GRAND alone will not be able to break the degeneracy between redshift evolution of the sources and their composition. Our findings underline the discriminating potential of next generation radio array detectors and motivate further efforts in this direction.

  • Hadronic tau decays as New Physics probes in the LHC era
    Phys.Rev.Lett. 122 (2019) 221801

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

    We analyze the sensitivity of hadronic τ decays to nonstandard interactions within the model-independent framework of the standard model effective field theory. Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the τ→ππντ channel representing an unexpected powerful new physics probe. We find that the ratios of nonstandard couplings to the Fermi constant are bound at the subpercent level. These bounds are complementary to the ones from electroweak precision observables and pp→τντ measurements at the LHC. The combination of τ decay and LHC data puts tighter constraints on lepton universality violation in the gauge boson-lepton vertex corrections.

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

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

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

  • Thermal neutrino portal to sub-MeV dark matter
    Phys.Rev. D99 (2019) 095030

    by: Berlin, Asher (SLAC) et al.

    Thermal relics lighter than an MeV contribute to the energy density of the universe at the time of nucleosynthesis and recombination. Constraints on extra radiation degrees of freedom typically exclude even the simplest of such dark sectors. We explore the possibility that a sub-MeV dark sector entered equilibrium with the Standard Model after neutrino-photon decoupling, which significantly weakens these constraints and naturally arises in the context of neutrino mass generation through the spontaneous breaking of the lepton number. Acquiring an adequate dark matter abundance independently motivates the MeV scale in these models through the coincidence of gravitational, matter-radiation equality, and neutrino mass scales, (mPl/TMRE)1/4mν∼MeV. This class of scenarios will be decisively tested by future measurements of the cosmic microwave background and matter structure of the universe. While the dark sector dominantly interacts with Standard Model neutrinos, large couplings to nucleons are possible in principle, leading to observable signals at proposed low-threshold direct detection experiments.

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

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

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

  • Azimuthal correlation function of polarized top quark in noncommutative space–time
    Annals Phys. 406 (2019) 71-85

    by: Rezaei, Z. (Yazd U.) et al.

    The azimuthal correlation belongs to a class of polarization observables which vanishes at the Born term level in the standard model for the semileptonic rest frame decay of a polarized top quark t(↑)→bW+→bℓ+υℓ . In this frame, the azimuthal correlation is defined between the planes formed by the vectors (p→ℓ,p→Xb) and (p→ℓ,P→t) . We calculate the azimuthal correlation function of polarized top quark in the framework of the noncommutative standard model for the first time. We find that this observable is nonzero in the leading order of noncommutative space–time. Further the appearance of the oscillatory azimuthal distribution of decay rate provides a practical possibility to test the noncommutativity in particle colliders.

  • Neutrino mass and dark energy constraints from redshift-space distortions
    JCAP 1905 (2019) 041

    by: Upadhye, Amol (Wisconsin U., Madison)

    Cosmology in the near future promises a measurement of the sum of neutrino masses ∑ mν, a fundamental Standard Model parameter, as well as substantially-improved constraints on the dark energy. We use the shape of the BOSS redshift-space galaxy power spectrum, in combination with CMB and supernova data, to constrain the neutrino masses and the dark energy. Essential to this calculation are several recent advances in non-linear cosmological perturbation theory, including fast Fourier transform methods, redshift space distortions, and scale-dependent growth. Our 95% confidence upper bound ∑ mν < 180 meV degrades substantially to ∑ mν < 540 meV when the dark energy equation of state and its first derivative are also allowed to vary, representing a significant challenge to current constraints. We also study the impact of additional galaxy bias parameters, finding that a greater allowed range of scale-dependent bias only slightly shifts the preferred ∑ mν, weakens its upper bound by ≈ 20%, and has a negligible effect on the other cosmological parameters.

  • Impact of standard neutrino oscillations and systematics in proton lifetime measurements
    J.Phys. G46 (2019) 075006

    by: Gratieri, D.R. (Campinas State U.) et al.

    We use atmospheric neutrino phenomenology to obtain the expected background to proton decay in large underground neutrino detectors, like DUNE. We introduced, for the first time in this kind of analysis, the experimentally confirmed neutrino oscillations of the atmospheric neutrino observations which reduce by a factor of 40\% the corresponding background for nucleon decay channel $p\rightarrow \mu^{+}+\pi^{0}$. Furthermore, we infer the impact of four systematics on such background: the overall efficiency, the muon reconstruction energy resolution, the resonant neutral pion cross-section and the neutral pion angular resolution. Considering a 40 kton detector with efficiency 45\%, our analysis leads to an error band in the lower limit for the proton lifetime, from $7.9 \times 10^{33}$~years to {\bf $1.1 \times 10^{34}$}~years at $90\%$~C.L.. These numbers can be compared with the current mode dependent experimental limits $\tau > 10^{31}-10^{33}$~years at $90\%$~C.L.. Finally we investigate how this limit can be further improved with the enhancement of the efficiency of the experiment which can be obtained, for instance, with the implementation of the ARAPUCA device in DUNE.

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