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  • Semileptonic and nonleptonic decays of $D$ into tensor mesons with light-cone sum rule
    Phys.Rev. D99 (2019) 013001

    by: Momeni, S. (Isfahan Tech. U.) et al.

    Form factors of D decays into JPC=2++ tensor mesons are calculated in the light-cone sum rules approach up to twist-4 distribution amplitudes of the tensor meson. The masses of the tensor mesons are comparable to that of the charm quark mass mc; therefore, all terms including powers of mT/mc are kept out in the expansion of the two-particle distribution amplitude ⟨T|q¯1α(x)q2δ(0)|0⟩. Branching ratios of the semileptonic D→Tμν¯μ decays and nonleptonic D→TP(P=K,π) decays are taken into consideration. A comparison is also made between our results and predictions of other methods and the existing experimental values for the nonleptonic case. The semileptonic branching ratios are typically of the order of 10-5, and the nonleptonic ones show better agreement with the experimental data in comparison to the Isgur-Scora-Grinstein-Wise predictions.

  • Neutral-current weak pion production off the nucleon in covariant chiral perturbation theory

    by: Yao, De-Liang
    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.

  • Spin-flavor oscillations of Dirac neutrinos in matter under the influence of a plane electromagnetic wave

    by: Dvornikov, Maxim
    We study oscillations of Dirac neutrinos in background matter and a plane electromagnetic wave. We find the new exact solution of the Dirac-Pauli equation for a massive neutrino with the anomalous magnetic moment electroweakly interacting with matter under the influence of a plane electromagnetic wave with the circular polarization. We use this result to describe neutrino spin oscillations in the external fields in question. Then we consider several neutrino flavors and study neutrino spin-flavor oscillations in this system. For this purpose we formulate the initial condition problem and solve it accounting for the considered external fields. We derive the analytical expressions for the transition probabilities for spin-flavor oscillations for different types of neutrino magnetic moments. These analytical expressions are compared with the numerical solutions of the effective Schrodinger equation and with the findings of other authors. Finally, we briefly discuss some possible astrophysical applications.

  • Fully Constrained Mass Matrix: Can Symmetries alone determine the Flavon Vacuum Alignments?

    by: Krishnan, R.
    A set of fully constrained Majorana neutrino mass matrices consistent with the experimental data was proposed in 2012. In the framework of the representation theory of finite groups, it was recently shown that a fully constrained mass matrix can be conveniently mapped into a sextet of $\Sigma(72\times 3)$. In this paper, we expand on this work and introduce a formalism to incorporate additional symmetries onto $\Sigma(72\times 3)$, so that the vacuum alignment of the sextet is entirely determined by the flavour symmetries alone. The complete flavour group is $\Sigma(72\times3)\times X_{24}\times X_{24}$ where $X_{24}$ is a finite group specifically constructed with the required symmetries. Here, we define several flavons which transform as multiplets under $\Sigma(72\times 3)$ as well as $X_{24}$. Our construction ensures that the vacuum alignment of each of these flavons is a simultaneous invariant eigenstate of specific elements of the groups $\Sigma(72\times 3)$ and $X_{24}$, i.e. the vacuum alignment is fully determined by its symmetries. The flavons couple together uniquely to reproduce the fully constrained sextet of $\Sigma(72\times 3)$.

  • Exotic Leptonic solutions to observed anomalies in lepton universality observables and more

    by: Dhargyal, Lobsang
    In this talk I will present the work that we did in \cite{1}\cite{2}\cite{3}\cite{4}\cite{5} related to observed lepton universality violation by Babar, Belle and LHCb in R($D^{(*)}$) and $R_{K^{(*)}}$ as well as the reported deviation in muon (g-2) by BNL. We had shown that all these anomalies as well as Baryon-genesis, Dark-matter and small neutrino masses could be explained by introducing new exotic scalars, leptons and scalar-leptoquarks only. It turn out that some of these models have very peculiar signatures such as prediction of existence of heavy stable charged particle \cite{1}\cite{2}, vector like fourth generation leptons \cite{3} or even scalar Baryonic DM candidates etc. Some of these models turn out to have very unique collider signatures as well such as $ee/pp \rightarrow \mu\mu(\tau\tau)\ +\ missing\ energy\ (ME)$, see \cite{1}\cite{2}\cite{4}. This is interesting in the sense that such peculiar signatures of these new particles can be searched in the upcoming HL-LHC or with even better chance of observing these signatures are in the upcoming precision machines such as ILC, CEPC etc.

  • Double-beta decay and its potential to explore beyond standard model physics
    Int.J.Mod.Phys. A33 (2018) 1845012

    by: Stoica, Sabin (Bucharest, IFIN-HH)

    Double-beta decay (DBD) is a rare nuclear process of great interest due to its potential to provide information about physics beyond the Standard Model (BSM). For example, the discovery of the neutrinoless double-beta (0νββ) decay mode could give information about important issues such as possible violations of Lorentz symmetry and lepton number, nature of neutrinos (are they Dirac- or Majorana-like particles?), neutrino absolute masses, neutrino mass hierarchy, existence of heavy (sterile) neutrinos, etc. In the theoretical study of DBD, one needs a precise calculation of the nuclear matrix elements (NMEs) and phase space factors (PSFs) entering the half-lives formulas, for different decay modes, transitions and mechanisms of occurrence. Reliable computations of these quantities may result in reliable predictions of DBD half-lives and constrains of the BSM parameters related to the possible mechanisms that can contribute to the 0νββ decay. In this paper, I briefly review the theoretical challenges in the study of 0νββ decay. I describe the computation of the NMEs and PSFs and present results for a number of selected nuclei. Then, I show the broader potential of this process to provide information about BSM physics and present new upper limits for parameters associated with light neutrino, heavy neutrino and SUSY exchange mechanisms. Finally, I suggest a more consistent approach to calculate the NMEs and PSFs, namely to compute directly their product and discuss some possibilities to reduce the errors related to the uncertain value of the axial-vector constant.

  • Spinor-vector duality and sterile neutrinos in string derived models
    LTH 1192

    by: Faraggi, Alon E. (Liverpool U., Dept. Math.)

    The MiniBooNE collaboration found evidence for the existence of sterile neutrinos, at a mass scale comparable to the active left-handed neutrinos. While sterile neutrinos arise naturally in large volume string scenarios, they are more difficult to accommodate in heterotic-string derived models that reproduce the GUT embedding of the Standard Model particles. Sterile neutrinos in heterotic-string models imply the existence of an additional Abelian gauge symmetry at low scales, possibly within reach of contemporary colliders. I discuss the construction of string derived Z' models that utilise the spinor-vector duality to guarantee that the extra $U(1)_{Z^\prime}$ symmetry can remain unbroken down to low scales.

  • Low-scale Leptogenesis with Minimal Lepton Flavour Violation

    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)

    by: Babu, K.S.
    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 $(M_{\rm PQ}/M_{\rm GUT})^2$, which enables all SUSY particles to have masses of order TeV. With TeV scale SUSY spectrum, $p \rightarrow \overline{\nu} K^+$ decay rate is predicted to be in the observable range. Lepton flavor violating processes $\mu \rightarrow e\gamma$ decay and $\mu-e$ conversion in nuclei, induced by the Dirac neutrino Yukawa couplings, are found to be within reach of forthcoming experiments.

  • Neutrino, parity violaton, V-A: a historical survey

    by: Hadjiivanov, Ludmil (Sofiya, Inst. Nucl. Res.)

    A concise story of the rise of the four fermion theory of the universal weak interaction and its experimental confirmation, with a special emphasis on the problems related to parity violation.

  • Effects of Violation of Equivalence Principle on UHE Neutrinos at IceCube in 4 Flavour Scenario

    by: Pandey, Madhurima (Saha Inst.)

    If weak equivalence principle is violated then different types of neutrinos would couple differently with gravity and that may produce a gravity induced oscillation for the neutrinos of different flavour. We explore here the possibility that very small violation of the principle of weak equivalence (VEP) can be probed by ultra high energy neutrinos from distant astrophysical sources. The very long baseline length and the ultra high energies of such neutrinos could be helpful to probe very small VEP. We consider a 4-flavour neutrino scenario (3 active + 1 sterile) with both mass-flavour and gravity induced oscillations and compare the detection signatures for these neutrinos (muon tracks and shower events) with and without gravity induced oscillations at a kilometer scale detector such as IceCube. We find that the muon track to shower ratios vary considerably (by a factor of $\sim 3.6$) when compared the estimation without any gravity induced oscillation (no VEP case).

  • Prompt atmospheric neutrinos in the quark-gluon string model
    Preprint of JINR P2-2018-4

    by: Sinegovsky, S.I. (Dubna, JINR) et al.

    We calculate the atmospheric flux of prompt neutrinos, produced in decays of the charmed particles at energies beyond 1 TeV. Cross sections of the D-mesons and ${\Lambda}^{+}_{c}$ baryons production in pA and $\pi$A collisions are calculated in the phenomenological quark-gluon string model (QGSM) which is updated with use of the recent measurements of cross sections of the charmed meson production in the LHC experiments. A new estimate of the prompt atmospheric neutrino flux is obtained and compared with the limit of the IceCube experiment as well as with predictions of other charm production models.

  • Trimaximal Neutrino Mixing from Modular A$_4$ Invariance with Residual Symmetries
    SISSA 57/2018/FISI

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

    We construct phenomenologically viable models of lepton masses and mixing based on modular $A_4$ invariance broken to residual symmetries $\mathbb{Z}^{T}_3$ or $\mathbb{Z}^{ST}_3$ and $\mathbb{Z}^S_2$ 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 $\theta_{23}$ and $\theta_{13}$, 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 $\theta_{12}$ and the angle $\theta_{13}$ (which determines $\theta_{12}$), ii) the values of the Dirac CPV phase $\delta$ and of the angles $\theta_{23}$ and $\theta_{13}$, iii) the sum of the neutrino masses and $\theta_{23}$, and iv) between the two Majorana phases.

  • Super-weak force and neutrino masses

    by: Trócsányi, Zoltán (Eotvos U.)

    We consider an anomaly free extension of the standard model gauge group GSM by an abelian group to GSM x U (1)Z . The condition of anomaly cancellation is known to fix the Z-charges of the particles, but two. We fix one remaining charge by allowing for all possible Yukawa interactions of the known left handed neutrinos and new right-handed ones that obtain their masses through interaction with a new scalar field with spontaneously broken vacuum. We discuss some of the possible consequences of the model. Assuming that the new interaction is responsible for the observed differences between the standard model prediction for the anomalous magnetic moment of the muon or anti-muon and their measured values, we predict the size of the vacuum expectation value of the new scalar field.

  • Probing the seesaw mechanism at the 250 GeV ILC

    by: Das, Arindam
    We consider a gauged U(1)$_{B-L}$ (Baryon-minus-Lepton number) extension of the Standard Model (SM), which is anomaly-free in the presence of three Right-Handed Neutrinos (RHNs). Associated with the U(1)$_{B-L}$ symmetry breaking the RHNs acquire their Majorana masses and then play the crucial role to generate the neutrino mass matrix by the seesaw mechanism. Towards the experimental confirmation of the seesaw mechanism, we investigate a RHN pair production through the U(1)$_{B-L}$ gauge boson ($Z^\prime$) at the 250 GeV International Linear Collider (ILC). The $Z^\prime$ gauge boson has been searched at the Large Hadron Collider (LHC) Run-2 and its production cross section is already severely constrained. The constraint will become more stringent by the future experiments with the High-Luminosity upgrade of the LHC (HL-LHC). We find a possibility that even after a null $Z^\prime$ boson search result at the HL-LHC, the 250 GeV ILC can search for the RHN pair production through the final state with same-sign dileptons plus jets, which is a `smoking-gun' signature from the Majorana nature of RHNs. In addition, some of RHNs are long-lived and leave a clean signature with a displaced vertex. Therefore, the 250 GeV ILC can operate as not only a Higgs Factory but also a RHN discovery machine to explore the origin of the Majorana neutrino mass generation, namely the seesaw mechanism.

  • The third family of neutrinos

    by: Blondel, Alain
    This paper retraces the 24 years starting with the appearance of the symbol "$\nu_{\tau}$" in 1977, until the observation of tau neutrino interactions with matter in 2000. The fact that the neutral particle present in tau decays was a neutrino was demonstrated by 1979; its existence as the third neutrino $\nu_{\tau}$, iso-spin partner of the tau lepton, was definitely established in 1981-1986; it was demonstrated that the number of light active neutrinos is closed with the known ones ($\nu_e, \nu_{\mu},\nu_{\tau}$) in 1989; before 2000 the $\nu_{\tau}$ properties had been precisely determined in $e^+e^-$ and $p\bar{p}$ collider experiments.

  • Resonant leptogenesis at TeV-scale and neutrinoless double beta decay

    by: Asaka, Takehiko
    We investigate a resonant leptogenesis scenario by quasi-degenerate right-handed neutrinos which have TeV-scale masses. Especially, we consider the case when two right-handed neutrinos are responsible to leptogenesis and the seesaw mechanism for active neutrino masses, and assume that the CP violation occurs only in the mixing matrix of active neutrinos. In this case the sign of the baryon asymmetry depends on the Dirac and Majorana CP phases as well as the mixing angle of the right-handed neutrinos. It is shown how the yield of the baryon asymmetry correlates with these parameters. In addition, we find that the effective neutrino mass in the neutrinoless double beta decay receives an additional constraint in order to account the observed baryon asymmetry.

  • Finite modular subgroups for fermion mass matrices and baryon/lepton number violation

    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.

  • Detecting a Secondary Cosmic Neutrino Background from Majoron Decays in Neutrino Capture Experiments

    by: Chacko, Zackaria (Maryland U.) et al.

    We consider theories in which the generation of neutrino masses is associated with the breaking of an approximate global lepton number symmetry. In such a scenario the spectrum of light states includes the Majoron, the pseudo-Nambu Goldstone boson associated with the breaking of the global symmetry. For a broad range of parameters, the Majoron decays to neutrinos at late times, after the cosmic neutrinos have decoupled from the thermal bath, resulting in a secondary contribution to the cosmic neutrino background. We determine the current bounds on this scenario, and explore the possibility of directly detecting this secondary cosmic neutrino background in experiments based on neutrino capture on nuclei. For Majoron masses in the eV range or below, the neutrino flux from these decays can be comparable to that from the primary cosmic neutrino background, making it a promising target for direct detection experiments. The neutrinos from Majoron decay are redshifted by the cosmic expansion, and exhibit a characteristic energy spectrum that depends on both the Majoron mass and its lifetime. For Majoron lifetimes of order the age of the universe or larger, there is also a monochromatic contribution to the neutrino flux from Majoron decays in the Milky Way that can be comparable to the diffuse extragalactic flux. We find that for Majoron masses in the eV range, direct detection experiments based on neutrino capture on tritium, such as PTOLEMY, will be sensitive to this scenario with 100 gram-years of data. In the event of a signal, the galactic and extragalactic components can be distinguished on the basis of their distinct energy distributions, and also by using directional information obtained by polarizing the target nuclei.

  • Singlet-doublet fermion and triplet scalar dark matter with radiative neutrino masses

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

    We present a detailed study of a combined singlet-doublet fermion and triplet scalar model for dark matter. These models have only been studied separately in the past. Together, they form a simple extension of the Standard Model that can account for dark matter and explain the existence of neutrino masses, which are generated radiatively. However, this also implies the existence of lepton flavour violating processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new $\mathbb{Z}_2$ symmetry to stabilise the dark matter candidate. We analyse the dark matter, neutrino mass and lepton flavour violation aspects both separately and in conjunction, exploring the viable parameter space of the model. This is done using a numerical random scan imposing successively the neutrino mass and mixing, relic density, Higgs mass, direct detection, collider and lepton flavour violation constraints. We find that dark matter in this model is fermionic for masses below about 1 TeV and scalar above. The narrow mass regions found previously for the two separate models are enlarged by their coupling. While coannihilations of the weak isospin partners are sizeable, this is not the case for fermions and scalars despite their often similar masses due to the relatively small coupling of the two sectors, imposed by the small neutrino masses. We observe a high degree of complementarity between direct detection and lepton flavour violation experiments, which should soon allow to fully probe the fermionic dark matter sector and at least partially the scalar dark matter sector.

  • On flavor-mass majorization uncertainty relations and their links to the mixing matrix

    by: Rastegin, Alexey E. (Irkutsk State U.)

    We consider uncertainties in the case of flavor and mass eigenstates of neutrinos from the viewpoint of majorization uncertainty relations. Nontrivial lower bounds are a reflection of the fact that neutrinos cannot be simultaneously in a flavor and mass eigenstate. As quantitative measures of uncertainties, both the R\'{e}nyi and Tsallis entropies are utilized. In a certain sense, majorization uncertainty relations are directly connected to measurement statistics. On the other hand, magnitudes of elements of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix are not known exactly. Hence, some conditions on applications of majorization uncertainty relations follow. We also discuss the case with detection inefficiencies, since it can naturally be incorporated into the entropic framework. Finally, some comments on applications of entropic uncertainty relations with quantum memory are given. The latter may be used in entanglement-assisted studying parameters of three-flavor neutrino oscillations.

  • On $\theta_{23}$ Octant Measurement in $3+1$ Neutrino Oscillations in T2HKK

    by: Haba, Naoyuki (Shimane U.) et al.

    It has been pointed out that the mixing of an eV-scale sterile neutrino with active flavors can lead to loss of sensitivity to $\theta_{23}$ octant (sign of $\sin^2\theta_{23}-1/2$) in long baseline experiments, because the main oscillation probability $P_0=4\sin^2\theta_{23}\sin^2\theta_{13}\sin^2\Delta_{13}$ can be degenerate with the sum of the interferences with the solar oscillation amplitude and an active-sterile oscillation amplitude in both neutrino and antineutrino oscillations, depending on CP phases. In this paper, we show that the above degeneracy is resolved by measuring the same beam at different baseline lengths. We demonstrate that Tokai-to-Hyper-Kamiokande-to-Korea (T2HKK) experiment (one 187~kton fiducial volume water Cerenkov detector is placed at Kamioka, $L=295$~km, and another detector is put in Korea, $L\sim1000$~km) exhibits a better sensitivity to $\theta_{23}$ octant in those parameter regions where the experiment with two detectors at Kamioka is insensitive to it. Therefore, if a hint of sterile-active mixings is discovered in short baseline experiments, T2HKK is a better option than the plan of placing two detectors at Kamioka. We also consider an alternative case where one detector is placed at Kamioka and a different detector is at Oki Islands, $L=653$~km, and show that this configuration also leads to a better sensitivity to $\theta_{23}$ octant.

  • Implementing the inverse type-II seesaw mechanism into the 3-3-1 model

    by: de Sousa Pires, Carlos Antônio (Paraiba U.) et al.

    After the LHC is turning on and accumulating more data, the TeV scale seesaw mechanisms for small neutrino masses are gaining more attention. One of the most popular realization of such mechanisms is the inverse seesaw mechanism. In this scenario, the lepton number is supposed to be explicitly violated at very low energy scale. As a result, it naturally provides neutrino masses at sub-eV scale and its signature can be probed at the LHC. Inverse seesaw mechanisms come in three different ways. Here we restrict our investigation to the inverse type II seesaw case where we implement it into the framework of the 3-3-1 model with right-handed neutrinos. Interestingly, we propose the mechanism which provides small masses to both the standard neutrinos as well as to the right-handed ones. The best signature is the doubly charged scalars which are the sextet. We investigate their production at the LHC through the process $\sigma (p\,p \rightarrow Z^*, \gamma^* ,Z^{\prime} \rightarrow \Delta^{++}\,\Delta^{--})$ and the signal through four leptons final state decay channel.

  • Testing of quasi-elastic neutrino charged-current and two-body meson exchange current models with the MiniBooNE neutrino data and analysis of these processes at energies available at the NOvA experiment

    by: Butkevich, A.V.
    The charged-current quasi-elastic (CCQE) scattering of muon neutrinos on a carbon target is analyzed using the relativistic distorted-wave impulse approximation (RDWIA) taking into account the contribution of the two-particle and two-hole meson exchange current ($2p-2h$ MEC) to the weak response functions. A fit the RDWIA+MEC model to the MiniBooNE neutrino data is performed and the best fit value of nucleon axial mass $M_A=1.2 \pm 0.06$ GeV is obtained. We also extract the values of the axial form factor $F_A(Q^2)$ as a function of the squared momentum transfer $Q^2$ from the measured $d\sigma/dQ^2$ cross section. The flux-integrated CCQE-like differential cross sections for neutrino scattering at energies of the NOvA experiment are estimated within the RDWIA+MEC approach.

  • Two simple textures of the magic neutrino mass matrix
    J.Phys. G46 (2019) 015001

    by: Channey, Kanwaljeet S. (Delhi U.) et al.

    The Tri-Bimaximal (TBM) mixing predicts a vanishing $\theta_{13}$. This can be attributed to the inherited $\mu-\tau$ symmetry of TBM mixing. We break its $\mu-\tau$ symmetry by adding a complex magic matrix with one variable to TBM neutrino mass matrix with one vanishing eigenvalue. We present two such textures and study their phenomenological implications.

  • Neutrino elastic scattering on polarized electrons as tool for probing neutrino nature

    by: Błaut, A. (Wroclaw U.) et al.

    Possibility of using the polarized electron target (PET) for testing the neutrino nature is considered. One assumes that the incoming electron neutrino ($\nu_e$) beam is the superposition of left chiral states with right chiral ones. Consequently the non--vanishing transversal components of $\nu_e$ spin polarization may appear, both T-even and T-odd. $\nu_e$s are produced by the low energy monochromatic (un)polarized emitter located at a near distance from the hypothetical detector which is able to measure both the azimuthal angle and polar angle of the recoil electrons, and/or also the energy of the outgoing electrons with a high resolution. A detection process is the elastic scattering of $\nu_e$s (Dirac or Majorana) on the polarized electrons. Left chiral (LC) $\nu_e$s interact mainly by the standard $V - A$ interaction, while right chiral (RC) ones participate only in the non-standard $V + A$, scalar $S_R$, pseudoscalar $P_R$ and tensor $T_R$ interactions. We show that a distinction between the Dirac and Majorana $\nu_e$s is possible both for the purely left chiral states and in the case of left-right superposition. We analyze the various types of azimuthal asymmetries of recoil electrons, the spectrum and the polar distribution of scattered electrons as tools for probing the $\nu_e$ nature and the effects of time reversal violation in the leptonic processes. The basic difference between the Dirac and Majorana $\nu_e$s arises from the absence of T and V interactions in the Majorana scenario. Moreover, in the Majorana case the cross section contains the non-vanishing interference between $V-A$ and $V+A$ interactions, proportional to the T-even longitudinal $\nu_e$ polarization. Our model-independent study is carried out for the flavor $\nu_e$ eigenstates in the relativistic $\nu_e$ limit.

  • Neutrino oscillations in accelerated frames
    EPL 124 (2018) 51001

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

    We discuss neutrino oscillations in vacuum from the point of view of a uniformly accelerated observer. A covariant definition of quantum phase is introduced with the aim of generalizing the standard expression of the oscillation amplitude to the accelerating frame. By way of illustration, we address a simplified two-flavor model with relativistic neutrinos, showing that inertial effects on the usual Pontecorvo formula are intimately related to the energy redshift. Phenomenological aspects are preliminarily analyzed in the context of atmospheric neutrinos. Finally, we discuss a gedanken experiment in order to investigate our formalism in regime of extreme acceleration.

  • Baryogenesis, Dark Matter, and Flavor Structure in Non-thermal Moduli Cosmology

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

    The appearance of scalar/moduli fields in the early universe, as motivated by string theory, naturally leads to non-thermal "moduli cosmology". Such cosmology provides a consistent framework where the generation of radiation, baryons, and dark matter can occur while maintaining successful Big Bang Nucleosynthesis and avoiding the cosmological moduli problem. We present a relatively economical construction with moduli cosmology, building on a variety of string-inspired components (e.g. supersymmetry, discrete symmetries, Green-Schwarz anomaly cancellation). We address a range of outstanding problems of particle physics and cosmology simultaneously, including the fermion mass hierarchy and flavor puzzle, the smallness of neutrino masses, baryogenesis and dark matter. Our setup, based on discrete $\mathrm{Z}_{12}^{R}$ symmetry and anomalous $\mathrm{U}(1)_A$, is void of the usual issues plaguing the Minimal Supersymmetric Standard Model, i.e. the $\mu$-problem and the overly-rapid proton decay due to dimension-4,-5 operators. The model is compatible with $\mathrm{SU}(5)$ Grand Unification. The smallness of Dirac neutrino masses is automatically established by requiring the cancellation of mixed gravitational-gauge anomalies. The decay of the moduli field provides a common origin for the baryon number and dark matter abundance, explaining the observed cosmic coincidences, $\Omega_{B} \sim \Omega_{DM}$.

  • Foraging for dark matter in large volume liquid scintillator neutrino detectors with multiscatter events

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

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

  • Correlations and degeneracies among the NSI parameters with tunable beams at DUNE

    by: Masud, Mehedi (Valencia U., IFIC) et al.

    The Deep Underground Neutrino Experiment (DUNE) is a leading experiment in neutrino physics which is presently under construction. DUNE aims to measure the yet unknown parameters in the three flavour oscillation scenario which includes discovery of leptonic CP violation, determination of the mass hierarchy and determination of the octant of $\theta_{23}$. Additionally, the ancillary goals of DUNE include probing the sub-dominant effects induced by new physics. A widely studied new physics scenario is that of nonstandard neutrino interactions (NSI) in propagation which impacts the oscillations of neutrinos. We consider some of the essential NSI parameters impacting the oscillation signals at DUNE and explore the space of NSI parameters as well as study their correlations among themselves and with the yet unknown CP violating phase, $\delta$ appearing in the standard paradigm. The experiment utilizes a wide band beam and provides us with a unique opportunity to utilize different beam tunes at DUNE. We demonstrate that combining information from different beam tunes (low energy, LE and medium energy, ME) available at DUNE impacts the ability to probe some of these parameters and leads to altering the allowed regions in two-dimensional space of parameters considered.

  • Ultrahigh-energy cosmic-ray nuclei and neutrinos from engine-driven supernovae

    by: Zhang, B. Theodore (Peking U., Beijing) et al.

    Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahigh-energy cosmic rays (UHECRs). We investigate acceleration and survival of UHECR nuclei in the external reverse shock scenario. With composition models used in Zhang et al. (2018), we calculate spectra of escaping cosmic rays and secondary neutrinos. If their local rate is $\sim1$% of the core-collapse supernova rate, the observed UHECR spectrum and composition can be explained with the total cosmic-ray energy ${\mathcal E}_{\rm cr}\sim10^{51}$ erg. The maximum energy of UHECR nuclei can reach $\sim 10^{20}-{10}^{21}\rm eV$. The diffuse flux of source neutrinos is predicted to be $\sim10^{-10}~{\rm GeV}~{\rm cm}^{-2}~{\rm s}^{-1}~{\rm sr}^{-1}$ in the 0.1-1 EeV range, satisfying nucleus-survival bounds. The associated cosmogenic neutrino flux is calculated, and shown to be comparable to the source neutrino flux. These ultrahigh-energy neutrinos can be detected by ultimate detectors such as the Giant Radio Askaryan Neutrino Detector and Probe Of Extreme Multi-Messenger Astrophysics.

  • Linear seesaw model with hidden $SU(2)_H \times U(1)_X$ gauge symmetry
    APCTP Pre2018 - 018

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

    We propose a linear seesaw model with a hidden gauge symmetry $SU(2)_H \times U(1)_X$ where two types of standard model singlet fermions in realizing a linear seesaw mechanism are unified into $SU(2)_H$ doublet. Then we formulate scalar and gauge sector, neutrino mass matrix and lepton flavor violations. In our gauge sector, $Z$-$Z'$ mixing appears after spontaneous symmetry breaking and we investigate constraint from $\rho$-parameter. In addition we discuss $Z'$ production at the large hadron collider via $Z$-$Z'$ mixing, where $Z'$ tends to dominantly decay into heavy neutrinos.

  • Testing New Physics Explanations of MiniBooNE Anomaly at Neutrino Scattering Experiments

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

    Testable neutrino mass generation models have recently been proposed as a solution to the MiniBooNE excess. In this article, we show how neutrino scattering experiments, such as MINER$\nu$A and CHARM-II, can probe this class of models. We argue that by using sideband measurements of neutrino-electron scattering, we can significantly explore the parameter space motivated by the MiniBooNE results. Our new constraints show that a simultaneous explanation of the angular and energy distributions of the excess is in tension with neutrino-electron scattering data. We also provide an outlook of upcoming measurements that could further probe the new physics models of interest. In the context of those future measurements, we highlight the importance of control samples and improved theoretical understanding of neutrino-nucleus cross sections in the search for new physics in neutrino experiments.

  • Neutrino spin oscillations in polarized matter

    by: Grigoriev, A. (Moscow, MIPT) et al.

    We study the neutrino spin oscillations, i.e. neutrino spin precession, caused by the neutrino interaction with matter polarized by external magnetic field (or, equivalently, by the interaction of the induced magnetic moment of a neutrino with the magnetic field). In the analysis, we consider realistic conditions inside supernovae and discuss both the Dirac and Majorana cases. We show that due to the interaction with the polarized matter a neutrino flux from a supernova suffers additional attenuation at low neutrino energies. We also show that when taken together the effects of conventional magnetic moment and polarized matter can cancel each other so that under certain condition the oscillations disappear. Consequently, we note that this can lead to the appearance of a characteristic maximum in the spectrum of electron neutrinos from supernovae.

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

    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.

  • Assessing the sensitivity of PINGU to effective dark matter-nucleon interactions

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

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

  • Natural Seesaw and Leptogenesis from Hybrid of High-Scale Type I and TeV-Scale Inverse

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

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

  • Symmetry Breaking and Reheating after Inflation in No-Scale Flipped SU(5)

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

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

  • Measuring the atmospheric neutrino oscillation parameters and constraining the $3+1$ neutrino model with ten years of ANTARES data

    by: Albert, A. (Strasbourg, IPHC) et al.

    The ANTARES neutrino telescope has an energy threshold of a few tens of GeV. This allows to study the phenomenon of atmospheric muon neutrino disappearance due to neutrino oscillations. In a similar way, constraints on the 3+1 neutrino model, which foresees the existence of one sterile neutrino, can be inferred. Using data collected by the ANTARES neutrino telescope from 2007 to 2016, a new measurement of $\Delta m^2_{32}$ and $\theta_{23}$ has been performed - which is consistent with world best-fit values - and constraints on the 3+1 neutrino model have been derived.

  • Scalar Non-Standard Interactions in Neutrino Oscillation

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

    Scalar nonstandard interactions (NSI) can introduce a matter effect for neutrinos propagating through medium and modify the behavior of neutrino oscillations. In contrast to the conventional one induced by the nonstandard interactions with vector mediator, the scalar NSI contributes as correction to the neutrino mass matrix rather than potential. Consequently, the effect of scalar NSI is energy independent while the one of vector NSI scales linearly with neutrino energy. This leads to significantly different phenomenological consequences in reactor, solar, atmospheric, and accelerator neutrino oscillation experiments. Especially the recent Borexino data prefers a nonzero scalar NSI $\eta_{ee} = - 0.16$. A synergy of different types of experiments, especially those with matter density variation, can identify the scalar NSI and help to guarantee the measurement of CP violation at accelerator experiments.

  • Cosmic neutrino background search experiments as decaying dark matter detectors

    by: McKeen, David (TRIUMF)

    We investigate the possibility that particles that are long-lived on cosmological scales, making up part or all of the dark matter, decay to neutrinos that have present day energies around an eV. The neutrinos from these decays can potentially be visible at experiments that hope to directly observe the cosmic neutrino background through neutrino capture on tritium, such as PTOLEMY. In the context of a simple model that can realize such decays, we discuss the allowed signatures at a PTOLEMY-like experiment given current cosmological constraints.

  • One-loop neutrino mass model with $SU(2)_L$ multiplet fields
    APCTP Pre2018 - 017

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

    We propose a one-loop neutrino mass model with several $SU(2)_L$ multiplet fermions and scalar fields in which the inert feature of a scalar to realize the one-loop neutrino mass can be achieved by the cancellation among Higgs couplings thanks to nontrivial terms in the Higgs potential. Then we discuss our typical cut-off scale by computing renormalization group equation for $SU(2)_L$ gauge coupling, lepton flavor violations, muon anomalous magnetic moment, possibility of dark matter candidate, neutrino mass matrix satisfying the neutrino oscillation data. Finally, we search for our allowed parameter region to satisfy all the constraints, and discuss a possibility of detecting new charged particles at large hadron collider.

  • Beyond the Standard Model Physics at the HL-LHC and HE-LHC

    by: Cid Vidal , X. (Santiago de Compostela U., IGFAE) et al.

    This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as $3$ ab$^{-1}$ of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as $15$ ab$^{-1}$ of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by $20-50\%$ on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will, generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics.

  • Machine learning classification: case of Higgs boson CP state in H to tau tau$ decay at LHC

    by: Lasocha, K. (Jagiellonian U.) et al.

    The Machine Learning (ML) techniques are rapidly finding their place as standard methods of the data analysis in High Energy Physics. In this paper we continue discussion on their application to measurement of the CP state of the Higgs boson discovered by Large Hadron Collider experiments at CERN laboratory in 2012. We consider measurement in the $H \to \tau \tau$ decay channel and use ML techniques to discriminate between models based on variables defined in the multi-dimensional phase-space. We discuss and quantify possible improvements for the two most sensitive decay modes: $\tau^\pm \to \rho^\pm \nu$ with $\rho^\pm \to \pi^\pm \pi^0$ and $\tau^\pm \to a_1^\pm \nu$ with $a_1^\pm \to \rho^0 \pi^\pm \to 3 \pi^\pm$. In previous publications information on the hadronic decay products of the $\tau$ leptons was used. Discriminating between Higgs boson CP state was studied as binary classification problem. Now we show how approximate constraints on the outgoing neutrinos momenta, not accessible in a direct way, can help to improve classification performance. Added to the ML clasification features significantly enhance the sensitivity for Higgs boson CP state. In principle all information is provided with 4-momenta of the final state particles present in the events. As we have observed in the past, not all of such information is straightforward to be identified in ML training. We investigate how optimised high-level features, like some angles of neutrino orientation, may improve ML results. This can be understood as an intermediate step toward choice of better classifiers where expert variables will not be necessary. For the performance comparison, in parallel to {\it Deep Learning Neural Network}, we use other ML methods: {\it Boosted Trees}, {\it Random Forest} and {\it Support Vector Machine}.

  • Representing seesaw neutrino models and their motion in lepton flavour space

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

    We discuss how seesaw neutrino models can be graphically represented in lepton flavour space. In particular we examine various popular models and show how this representation helps understanding their properties and connection with experimental data. We also introduce a new matrix, the bridging matrix, that brings from the light to the heavy neutrino mass flavour basis, showing how this is related to the orthogonal matrix and how different quantities are easily expressed through it. We then show how, using the Haar measure, one can randomly generate orthogonal and the leptonic mixing matrices uniformly covering all flavour space in an unbiased way. Using the isomorphism between the group of complex rotations and the Lorentz group we introduce the concept of Lorentz boost in flavour space for a seesaw model and how this has an insightful physical interpretation. Finally, as an application we consider $N_2$-leptogenesis. Using current experimental values of low energy neutrino parameters, we show that the probability that at least one flavoured decay parameter of the lightest right-handed neutrino is smaller than unity is about $23\%$ (to be compared with the tiny probability that the total decay parameter is smaller than unity, $P(K_{\rm I}< 1)\sim 0.1 \%$, confirming the crucial role played by flavour effects). On the other hand when $m_1 \gtrsim 0.1\,{\rm eV}$ this probability reduces to less than $5\%$, showing how also $N_2$ leptogenesis requires hierarchical light neutrinos.

  • The effective neutrino approximation

    by: Alikhanov, I. (Moscow, INR)

    We propose to exploit the concept of effective (equivalent) particle in studies of neutrino interactions. A charged lepton is able to manifest itself, with a certain probability, as the corresponding neutrino. We derive the distributions of the effective neutrinos in the leptons. This is analogous to the parton densities in hadrons introduced in order to investigate dynamical properties of quarks and gluons unavailable in free states. The effective neutrino approximation may provide a framework for probing neutrino-induced reactions at $e^+e^-$ and $ep$ colliders as well as at other lepton colliding facilities. We give two examples of its application to electron--positron collisions.

  • Angular and CP-violation analyses of $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays at hadron collider experiments

    by: Marangotto, Daniele (INFN, Milan)

    The $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ branching fraction ratio $R(D^{*})$ has shown intriguing discrepancies between the Standard Model prediction and measurements performed at BaBar, Belle and LHCb experiments, a possible sign of beyond the Standard Model physics. Theoretical studies prove how observables related to the $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ differential decay distribution can be used to further constrain New Physics contributions, but their experimental measurements is lacking to date. This article presents the attainable precision on the measurement of $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ angular and CP-violating observables by exploiting approximate reconstruction algorithms using information from detectable final-state particles only, a case of special interest for hadron collider experiments. The resolution on the phase space variables is studied using $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays simulated in a forward detector geometry like LHCb. A novel method to correct the observable values for the reconstruction inaccuracies based on detector simulation is successfully tested on simulated data and the decrease in precision with respect to a perfect reconstruction is evaluated. The $D^{*+}$ longitudinal polarization fraction and one of the CP-violating observables can be measured losing a factor 2 and 5 in precision, respectively. The extraction of phase space distributions from the template fit selecting $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays and associated systematic uncertainties are also discussed.

  • Heavy neutral leptons and high-intensity observables
    LPT-Orsay-18-86 Phys. 6 (2018) 142

    by: Abada, Asmaa (Orsay, LPT) et al.

    New Physics models in which the Standard Model particle content is enlarged via the addition of sterile fermions remain among the most minimal and yet most appealing constructions, particularly since these states are present as building blocks of numerous mechanisms of neutrino mass generation. Should the new sterile states have non-negligible mixings to the active (light) neutrinos, and if they are not excessively heavy, one expects important contributions to numerous high-intensity observables, among them charged lepton flavour violating muon decays and transitions, and lepton electric dipole moments. We briefly review the prospects of these minimal SM extensions to several of the latter observables, considering both simple extensions and complete models of neutrino mass generation. We emphasise the existing synergy between different observables at the Intensity Frontier, which will be crucial in unveiling the new model at work.

  • Dark matter imprint on $^8$B neutrino spectrum
    Phys.Rev. D99 (2019) 023008

    by: Lopes, Ilídio (Lisbon, CENTRA) et al.

    The next generation of solar neutrino detectors will provide a precision measure of the $^8$B electron-neutrino spectrum in the energy range from 1-15 MeV. Although the neutrino spectrum emitted by $^8$B $\beta$-decay reactions in the Sun's core is identical to the neutrino spectrum measured in the laboratory, due to vacuum and matter flavour oscillations, this spectrum will be very different from that measured on Earth by the different solar neutrino experiments. We study how the presence of dark matter (DM) in the Sun's core changes the shape of the $^8$B electron-neutrino spectrum. These modifications are caused by local variations of the electronic density and the $^8$B neutrino source, induced by local changes of the temperature, density and chemical composition. Particularly relevant are the shape changes at low and medium energy range ($E_\nu\le 10 {\; \rm MeV}$), for which the experimental noise level is expected to be quite small. If such a distortion in the $^8$B$\nu_e$ spectrum were to be observed, this would strongly hint in favor of the existence of DM in the Sun's core. The $^8$B electron-neutrino spectrum provides a complementary method to helioseismology and total neutrino fluxes for constraining the DM properties. In particular, we study the impact of light asymmetric DM on solar neutrino spectra. Accurate neutrino spectra measurements could help to determine whether light asymmetric DM exists in the Sun's core, since it has been recently advocated that this type of DM might resolve the solar abundance problem.

  • Lepton masses and mixings in a $T'$ flavoured 3-3-1 model with type I and II seesaw mechanisms
    Mod.Phys.Lett. A34 (2019) 1950005

    by: Vien, V.V. (Duy Tan U.) et al.

    We propose a renormalizable $T'$ flavor model based on the $SU(3)_C\times SU(3)_L\times U(1)_X\times U(1)_{\mathcal{L}}$ gauge symmetry, consistent with the observed pattern of lepton masses and mixings. The small masses of the light active neutrinos are produced from an interplay of type I and type II seesaw mechanisms, which are induced by three heavy right-handed Majorana neutrinos and three $SU(3)_L$ scalar antisextets, respectively. Our model is only viable for the scenario of normal neutrino mass hierarchy, where the obtained physical observables of the lepton sector are highly consistent with the current neutrino oscillation experimental data. In addition, our model also predicts an effective Majorana neutrino mass parameter of $m_{\beta} \sim 1.41541\times 10^{-2}$ eV, a Jarlskog invariant of the order of $J_{CP}\sim -0.032$ and a leptonic Dirac CP violating phase of $\de = 238^\circ$, which is inside the $1\sigma$ experimentally allowed range.

  • Model independent study for the anomalous quartic $WW\gamma\gamma$ couplings at Future Electron-Proton Colliders

    by: Ari, V. (Ankara U.) et al.

    The Large Hadron Electron Collider and the Future Circular Collider-hadron electron with high center-of-mass energy and luminosity allow to better understand the Standard Model and to examine new physics beyond the Standard Model in the electroweak sector. Multi-boson processes permit for a measurement of the gauge boson self-interactions of the Standard Model that can be used to determine the anomalous gauge boson couplings. For this purpose, we present a study of the process $ep \rightarrow \nu_{e} \gamma \gamma j$ at the Large Hadron Electron Collider with center-of-mass energies of 1.30, 1.98 TeV and at the Future Circular Collider-hadron electron with center-of-mass energies of 7.07, 10 TeV to interpret the anomalous quartic $WW\gamma\gamma$ gauge couplings using a model independent way in the framework of effective field theory. We obtain the sensitivity limits at $95\%$ Confidence Level on 13 different anomalous couplings arising from dimension-8 operators.

  • Neutrinoless Double Beta Decay and Light Sterile Neutrino
    J.Korean Phys.Soc. 73 (2018) 1625-1630

    by: Jang, C.H. (Chung-Ang U.) et al.

    Recent neutrino experiment results show a preference for the normal neutrino mass ordering. The global efforts to search for neutrinoless double beta decays undergo a broad gap with the approach to the prediction in the three-neutrino framework based on the normal ordering. This research is intended to show that it is possible to find a neutrinoless double beta decay signal even with normal ordered neutrino masses. We propose the existence of a light sterile neutrino as a solution to the higher effective mass of the electron neutrino expected by the current experiments. A few short-baseline oscillation experiments gave rise to a limit on the mass of the sterile neutrino and its mixing with the lightest neutrino. We demonstrate that the results of neutrinoless double beta decays can also narrow down the range of the mass and the mixing angle of the light sterile neutrino.

  • Effect of Siegert's Theorem on Low-Energy Neutrino-Nucleus Interactions
    Phys.Rev. C98 (2018) 065505

    by: Hayes, A.C.
    We examine the importance of conserving the vector current in calculating low-energy neutrino-nucleus interactions by implicitly invoking Siegert's Theorem in describing the vector transverse electric current. We find that at low neutrino energies (E? <50 MeV), Siegert's Theorem can change neutrino cross sections for normal-parity non-spin-flip excitations by about a factor of two.The same is true of muon capture rates. At higher neutrino energies the effect of Siegert's Theorem diminishes, and by about 100 MeV the effect is very small.

  • Confronting SUSY SO(10) with updated Lattice and Neutrino Data
    JHEP 1901 (2019) 005

    by: Deppisch, Thomas (KIT, Karlsruhe, TTP) et al.

    We present an updated fit of supersymmetric SO(10) models to quark and lepton masses and mixing parameters. Including latest results from lattice QCD determinations of quark masses and neutrino oscillation data, we show that fits neglecting supersymmetric threshold corrections are strongly disfavoured in our setup. Only when we include these corrections we find good fit points. We present χ$^{2}$-profiles for the threshold parameters, which show that in our setup the thresholds related to the third generation of fermions exhibit two rather narrow minima.

  • Generalized Pauli–Gursey transformation and Majorana neutrinos
    Phys.Lett. B789 (2019) 76-81

    by: Fujikawa, Kazuo (Wako, RIKEN)

    We discuss a generalization of the Pauli-Gursey transformation, which is motivated by the Autonne-Takagi factorization, to an arbitrary $n$ number of generations of neutrinos using $U(2n)$ that defines general canonical transformations and diagonalizes symmetric complex Majorana mass matrices in special cases. The Pauli-Gursey transformation mixes particles and antiparticles and thus changes the definition of the vacuum and C. We define C, P and CP symmetries at each Pauli frame specified by a generalized Pauli-Gursey transformation. The Majorana neutrinos in the C and P violating seesaw model are then naturally defined by a suitable choice of the Pauli frame, where only Dirac-type fermions appear with well-defined C, P and CP, and thus the C symmetry for Majorana neutrinos agrees with the C symmetry for Dirac-type fermions. This fully symmetric setting corresponds to the idea of Majorana neutrinos as Bogoliubov quasi-particles. In contrast, the conventional direct construction of Majorana neutrinos in the seesaw model, where CP is well-defined but C and P are violated, encounters the mismatch of C symmetry for Majorana neutrinos and C symmetry for chiral fermions; this mismatch is recognized as the inevitable appearance of the singlet (trivial) representation of C symmetry for chiral fermions.

  • Time-varying neutrino mass from a supercooled phase transition: current cosmological constraints and impact on the $\Omega_m$-$\sigma_8$ plane
    Phys.Rev. D99 (2019) 023501

    by: Lorenz, Christiane S. (Oxford U.) et al.

    In this paper we investigate a time-varying neutrino mass model, motivated by the mild tension between cosmic microwave background (CMB) measurements of the matter fluctuations and those obtained from low-redshift data. We modify the minimal case of the model proposed by [G. Dvali and L. Funcke, Phys. Rev. D 93, 113002 (2016)PRVDAQ2470-001010.1103/PhysRevD.93.113002] that predicts late neutrino mass generation in a postrecombination cosmic phase transition, by assuming that neutrino asymmetries allow for the presence of relic neutrinos in the late-time Universe. We show that, if the transition is supercooled, current cosmological data (including CMB temperature, polarization and lensing, baryon acoustic oscillations, and type Ia supernovae) prefer the scale factor as of the phase transition to be very large, peaking at as∼1, and therefore supporting a cosmological scenario in which neutrinos are almost massless until very recent times. We find that in this scenario the cosmological bound on the total sum of the neutrino masses today is significantly weakened compared to the standard case of constant-mass neutrinos, with ∑mν<4.8  eV at 95% confidence, and in agreement with the model predictions. The main reason for this weaker bound is a large correlation arising between the dark energy and neutrino components in the presence of false vacuum energy that converts into the nonzero neutrino masses after the transition. This result provides new targets for the coming KATRIN and PTOLEMY experiments. We also show that the time-varying neutrino mass model considered here does not provide a clear explanation of the existing cosmological Ωm-σ8 discrepancies.

  • Constraining the invisible neutrino decay with KM3NeT-ORCA
    Phys.Lett. B789 (2019) 472-479

    by: de Salas, P.F. (Valencia U., IFIC) et al.

    Several theories of particle physics beyond the Standard Model consider that neutrinos can decay. In this work we assume that the standard mechanism of neutrino oscillations is altered by the decay of the heaviest neutrino mass state into a sterile neutrino and, depending on the model, a scalar or a Majoron. We study the sensitivity of the forthcoming KM3NeT-ORCA experiment to this scenario and find that it could improve the current bounds coming from oscillation experiments, where three-neutrino oscillations have been considered, by roughly two orders of magnitude. We also study how the presence of this neutrino decay can affect the determination of the atmospheric oscillation parameters sin2⁡θ23 and Δm312 , as well as the sensitivity to the neutrino mass ordering.

  • The experimental status of direct searches for exotic physics beyond the standard model at the Large Hadron Collider
    Rev.Phys. (2018) 100027
    Rev.Phys. 4 (2019) 100027

    by: Rappoccio, Salvatore (SUNY, Buffalo)

    The standard model of particle physics is an extremely successful theory of fundamental interactions, but it has many known limitations. It is therefore widely believed to be an effective field theory that describes interactions near the TeV scale. A plethora of strategies exist to extend the standard model, many of which contain predictions of new particles or dynamics that could manifest in proton-proton collisions at the Large Hadron Collider (LHC). As of now, none have been observed, and much of the available phase space for natural solutions to outstanding problems is excluded. If new physics exists, it is therefore either heavy (i.e. above the reach of current searches) or hidden (i.e. currently indistinguishable from standard model backgrounds). We summarize the existing searches, and discuss future directions at the LHC.

  • Comment on "keV Neutrino Dark Matter in a Fast Expanding Universe" by Biswas et al
    Phys.Lett. B789 (2019) 603-604

    by: Fernandez, Nicolas (UC, Santa Cruz) et al.

    Biswas et al. found that the thermal relic density of a dark matter particle freezing out while the universe's energy density is dominated by a non-standard extra component $\phi$, whose energy density redshifts faster than radiation, can be greatly suppressed. Here we show that this result, which contradicts extensive previous literature, is incorrect: the mistake lies with the assumption that the (decoupled) extra component $\phi$ contributes to the entropic degrees of freedom relevant for dark matter freeze out. If this were the case, a completely different approach would be needed to calculate the dark matter relic abundance, with dramatically different results.

  • Neutrino Charge Radii from COHERENT Elastic Neutrino-Nucleus Scattering
    Phys.Rev. D98 (2018) 113010

    by: Cadeddu, M. (Cagliari U.) et al.

    Coherent elastic neutrino-nucleus scattering is a powerful probe of neutrino properties, in particular of the neutrino charge radii. We present the bounds on the neutrino charge radii obtained from the analysis of the data of the COHERENT experiment. We show that the time information of the COHERENT data allows us to restrict the allowed ranges of the neutrino charge radii, especially that of $\nu_{\mu}$. We also obtained for the first time bounds on the neutrino transition charge radii, which are quantities beyond the Standard Model.

  • Unitarity Bounds of Astrophysical Neutrinos
    Phys.Rev. D98 (2018) 123023

    by: Ahlers, Markus (Bohr Inst.) et al.

    The flavor composition of astrophysical neutrinos observed at neutrino telescopes is related to the initial composition at their sources via oscillation-averaged flavor transitions. If the time evolution of the neutrino flavor states is unitary, the probability of neutrinos changing flavor is solely determined by the unitary mixing matrix that relates the neutrino flavor and propagation eigenstates. In this paper we derive general bounds on the flavor composition of TeV-PeV astrophysical neutrinos based on unitarity constraints. These bounds are useful for studying the flavor composition of high-energy neutrinos, where energy-dependent non-standard flavor mixing can dominate over the standard mixing observed in accelerator, reactor, and atmospheric neutrino oscillations.

  • MiniBooNE, MINOS+ and IceCube data imply a baroque neutrino sector
    Phys.Rev. D99 (2019) 015016

    by: Liao, Jiajun (Hawaii U.) et al.

    The 4.8$\sigma$ anomaly in MiniBooNE data cannot be reconciled with MINOS+ and IceCube data within the vanilla framework of neutrino oscillations involving an eV-mass sterile neutrino. We show that an apparently consistent picture can be drawn if charged-current and neutral-current nonstandard neutrino interactions are at work in the 3+1 neutrino scheme. It appears that either the neutrino sector is more elaborate than usually envisioned, or one or more datasets needs revision.

  • Dark Tridents at Off-Axis Liquid Argon Neutrino Detectors
    JHEP 1901 (2019) 001

    by: de Gouvêa, André (Northwestern U.) et al.

    We present dark tridents, a new channel for exploring dark sectors in short-baseline neutrino experiments. Dark tridents are clean, distinct events where, like neutrino tridents, the scattering of a very weakly coupled particle leads to the production of a lepton--antilepton pair. Dark trident production occurs in models where long-lived dark-sector particles are produced along with the neutrinos in a beam-dump environment and interact with neutrino detectors downstream, producing an on-shell boson which decays into a pair of charged leptons. We focus on a simple model where the dark matter particle interacts with the standard model exclusively through a dark photon, and concentrate on the region of parameter space where the dark photon mass is smaller than twice that of the dark matter particle and hence decays exclusively into standard-model particles. We compute event rates and discuss search strategies for dark tridents from dark matter at the current and upcoming liquid argon detectors aligned with the Booster beam at Fermilab -- MicroBooNE, SBND, and ICARUS -- assuming the dark sector particles are produced off-axis in the higher energy NuMI beam. We find that MicroBooNE has already recorded enough data to be competitive with existing bounds on this dark sector model, and that new regions of parameter space will be probed with future data and experiments.

  • Review of Lepton Universality tests in $B$ decays
    J.Phys. G46 (2019) 023001

    by: Bifani, Simone (Birmingham U.) et al.

    Several measurements of tree- and loop-level b-hadron decays performed in the recent years hint at a possible violation of Lepton Universality. This article presents an experimental and theoretical overview of the current status of the field.

  • Potential for probing three-body decays of Long-Lived Particles with MATHUSLA
    Phys.Lett. B789 (2019) 127-131

    by: Ibarra, Alejandro (Munich, Tech. U.) et al.

    Several extensions of the Standard Model predict the existence of Long-Lived Neutral Particles (LLNPs) with masses in the multi-GeV range and decay lengths of O(100 m) or longer. These particles could be copiously produced at the LHC, but the decay products cannot be detected with the ATLAS or CMS detectors. MATHUSLA is a proposed large-volume surface detector installed near ATLAS or CMS aimed to probe scenarios with LLNPs which offers good prospects for disentangling the physics underlying two-body decays into visible particles. In this work we focus on LLNP decays into three particles with one of them being invisible, which are relevant for scenarios with low scale supersymmetry breaking, feebly interacting dark matter or sterile neutrinos, among others. We analyze the MATHUSLA prospects to discriminate between two- and three-body LLNP decays, as well as the prospects for reconstructing the underlying model parameters.

  • Addressing the Majorana vs. Dirac Question with Neutrino Decays
    Phys.Lett. B789 (2019) 488-495

    by: Balantekin, A. Baha (Wisconsin U., Madison) et al.

    The Majorana versus Dirac nature of neutrinos remains an open question. This is due, in part, to the fact that virtually all the experimentally accessible neutrinos are ultra-relativistic. Noting that Majorana neutrinos can behave quite differently from Dirac ones when they are non-relativistic, we show that, at leading order, the angular distribution of the daughters in the decay of a heavy neutrino into a lighter one and a self-conjugate boson is isotropic in the parent's rest frame if the neutrinos are Majorana, independent of the parent's polarization. If the neutrinos are Dirac fermions, this is, in general, not the case. This result follows from CPT invariance and is independent of the details of the physics responsible for the decay. We explore the feasibility of using these angular distributions -- or, equivalently, the energy distributions of the daughters in the laboratory frame -- in order to address the Majorana versus Dirac nature of neutrinos if a fourth, heavier neutrino mass eigenstate reveals itself in the current or next-generation of high-energy colliders, intense meson facilities, or neutrino beam experiments.

  • Model-Independent Prediction of $R(\eta_c)$
    JHEP 1812 (2018) 114

    by: Berns, Anson (Montgomery Blair High School) et al.

    We present a model-independent prediction for $R(\eta_c) \! \equiv \! \mathcal{BR} (B_c \rightarrow \eta_c \, \tau^+\nu_\tau)/ \mathcal{BR} (B_c \rightarrow \eta_c \, \mu^+\nu_\mu)$. This prediction is obtained from the form factors through a combination of dispersive relations, heavy-quark relations at zero-recoil, and the limited existing determinations from lattice QCD. The resulting prediction, $R(\eta_c)=0.29(5)$, agrees with the weighted average of previous model predictions, but with reduced uncertainties.

  • Baryon-Lepton Duplicity as the Progenitor of Long-Lived Dark Matter
    UCRHEP-T593 (Aug 2018)
    Phys.Lett. B788 (2019) 442-445

    by: Ma, Ernest (UC, Riverside)

    In an SU(2)R extension of the standard model, it is shown how the neutral fermion N in the doublet (N,e)R may be assigned baryon number B=1 , in contrast to its SU(2)L counterpart ν in the doublet (ν,e)L which has lepton number L=1 . This baryon-lepton duplicity allows a scalar σ which couples to NLNL to be long-lived dark matter.

  • Cosmic infrared background excess from axionlike particles and implications for multimessenger observations of blazars
    Phys.Rev. D99 (2019) 023002

    by: Kalashev, Oleg E. (Moscow, INR) et al.

    The first measurement of the diffuse background spectrum at 0.8-1.7 $\mu \rm{m}$ from the CIBER experiment has revealed a significant excess of the cosmic infrared background (CIB) radiation compared to the theoretically expected spectrum. We revisit the hypothesis that decays of axionlike particle (ALP) can explain this excess, extending previous analyses to the case of a warm relic population. We show that such a scenario is not excluded by anisotropy measurements nor by stellar cooling arguments. Moreover, we find that the increased extragalactic background light (EBL) does not contradict observations of blazar spectra. Furthermore, the increased EBL attenuates the diffuse TeV gamma-ray flux and alleviates the tension between the detected neutrino and gamma ray fluxes.

  • Neutrino scattering and B anomalies from hidden sector portals
    JHEP 1901 (2019) 091

    by: Datta, Alakabha (Mississippi U.) et al.

    We examine current constraints on and the future sensitivity to the strength of couplings between quarks and neutrinos in the presence of a form factor generated from loop effects of hidden sector particles that interact with quarks via new interactions. We consider models associated with either vector or scalar interactions of quarks and leptons generated by hidden sector dynamics. We study constraints on these models using data from coherent elastic neutrino-nucleus scattering and solar neutrino experiments and demonstrate how these new interactions may be discovered by utilizing the recoil spectra. We show that our framework can be naturally extended to explain the lepton universality violating neutral current B decay anomalies, and that in a model framework the constraints from neutrino scattering can have implications for these anomalies.

  • Neutrino spin and spin-flavour oscillations in transversal matter currents with standard and non-standard interactions
    Phys.Rev. D98 (2018) 113009

    by: Pustoshny, Pavel (Moscow State U.) et al.

    After a brief history of two known types of neutrino mixing and oscillations, including neutrino spin and spin-flavor oscillations in the transversal magnetic field, we perform a systematic study of a new phenomenon of neutrino spin and spin-flavor oscillations engendered by the transversal matter currents on the bases of the developed quantum treatment of the phenomenon. Possibilities for the resonance amplification of these new types of oscillations by the longitudinal matter currents and longitudinal magnetic fields are analyzed. Neutrino spin-flavor oscillations engendered by the transversal matter currents in the case of nonstandard interactions of neutrinos with background matter are also considered.

  • Simplest Scoto-Seesaw Mechanism
    Phys.Lett. B789 (2019) 132-136

    by: Rojas, Nicolás (Santa Maria U., Valparaiso) et al.

    By combining the simplest (3,1) version of the seesaw mechanism containing a single heavy "right-handed" neutrino with the minimal scotogenic approach to dark matter, we propose a theory for neutrino oscillations. The "atmospheric" mass scale arises at tree level from the seesaw, while the "solar" oscillation scale emerges radiatively, through a loop involving the "dark sector" exchange. Such simple setup gives a clear interpretation of the neutrino oscillation lengths, has a viable WIMP dark matter candidate, and implies a lower bound on the neutrinoless double beta decay rate.

  • Radiative neutrino mass via fermion kinetic mixing
    Phys.Rev. D98 (2018) 115025

    by: Kang, Sin Kyu (Seoul, Nat. U. Technol.) et al.

    We propose that the radiative generation of the neutrino mass can be achieved by incorporating the kinetic mixing of fermion fields which arises radiatively at one-loop level. As a demonstrative example of the application of the mechanism, we present the particular case of the Standard Model extension by $U(1)_D$ symmetry. As a result, we show how neutrino masses can be generated via a kinetic mixing portal instead of a mass matrix with residual symmetries responsible for the stability of multicomponent dark matter.

  • Sterile Neutrino Dark Matter
    Prog.Part.Nucl.Phys. 104 (2019) 1-45

    by: Boyarsky, A. (Leiden U.) et al.

    We review sterile neutrinos as possible Dark Matter candidates. After a short summary on the role of neutrinos in cosmology and particle physics, we give a comprehensive overview of the current status of the research on sterile neutrino Dark Matter. First we discuss the motivation and limits obtained through astrophysical observations. Second, we review different mechanisms of how sterile neutrino Dark Matter could have been produced in the early universe. Finally, we outline a selection of future laboratory searches for keV-scale sterile neutrinos, highlighting their experimental challenges and discovery potential.

  • Limits on Neutrino Lorentz Violation from Multimessenger Observations of TXS 0506+056
    Phys.Lett. B789 (2019) 352-355

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

    The observation by the IceCube Collaboration of a high-energy ($E \gtrsim 200$ TeV) neutrino from the direction of the blazar TXS 0506+056 and the coincident observations of enhanced $\gamma$-ray emissions from the same object by MAGIC and other experiments can be used to set stringent constraints on Lorentz violation in the propagation of neutrinos that is linear in the neutrino energy: $\Delta v = - E/M_1$, where $\Delta v$ is the deviation from the velocity of light, and $M_1$ is an unknown high energy scale to be constrained by experiment. Allowing for a difference in neutrino and photon propagation times of $\sim 10$ days, we find that $M_1 \gtrsim 3 \times 10^{16}$ GeV. This improves on previous limits on linear Lorentz violation in neutrino propagation by many orders of magnitude, and the same is true for quadratic Lorentz violation.

  • Scrutinizing Right-Handed Neutrino Portal Dark Matter With Yukawa Effect
    Phys.Lett. B788 (2019) 530-534

    by: Bandyopadhyay, Priyotosh (Indian Inst. Tech., Hyderabad) et al.

    Analyzing the neutrino Yukawa effect in the freeze-out process of a generic dark matter candidate with right-handed neutrino portal, we identify the parameter regions satisfying the observed dark matter relic density as well as the current Fermi-LAT and H.E.S.S. limits and the future CTA reach on gamma-ray signals. In this scenario the dark matter couples to the Higgs boson at one-loop level and thus could be detected by spin-independent nucleonic scattering for a reasonable range of the relevant parameters.

  • Interpretation of the coincident observation of a high energy neutrino and a bright flare
    Nat.Astron. 3 (2019) 88-92

    by: Gao, Shan (DESY, Zeuthen) et al.

    On September 22nd 2017, the IceCube Neutrino Observatory reported a muon track from a neutrino with a very good positional accuracy. The alert triggered a number of astronomical follow-up campaigns, and the Fermi gamma-ray telescope found as counterpart an object named TXS0506+056 in a very bright, flaring state; this observation may be the first direct evidence for an extragalactic source of very high-energy cosmic rays. While this and subsequent observations provide the observational picture across the electromagnetic spectrum, answering where in the spectrum signatures of cosmic rays arise and what the source properties must be, given the observational constraints, requires a self-consistent description of the processes at work. Here we perform a detailed time-dependent modeling of these relevant processes and study a set of self-consistent models for the source. We find a slow but over-proportional increase of the neutrino flux during the flare compared to the production enhancement of energetic cosmic rays. We also demonstrate that interactions of energetic cosmic-ray ions result in predominantly hard X-ray emission, strongly constraining the expected number of neutrinos, and to a lesser degree in TeV gamma rays. Optical photons and GeV-scale gamma rays are predominantly radiated by electrons. Our results indicate that especially future X-ray and TeV-scale gamma-ray observations of nearby objects can be used to identify more such events.

  • Beta and Neutrinoless Double Beta Decays with KeV Sterile Fermions
    JHEP 1901 (2019) 041

    by: Abada, Asmaa (Orsay, LPT) et al.

    Motivated by the capability of the KATRIN experiment to explore the existence of KeV neutrinos in the $[1-18.5]$ KeV mass range, we explore the viability of minimal extensions of the Standard Model involving sterile neutrinos (namely the 3 + $N$ frameworks) and study their possible impact in both the beta energy spectrum and the neutrinoless double beta decay effective mass, for the two possible ordering cases for the light neutrino spectrum. We also explore how both observables can discriminate between motivated low-scale seesaw realizations involving KeV sterile neutrinos. Our study concerns the prospect of a Type-I seesaw with two right-handed neutrinos, and a combination of the inverse and the linear seesaws where the Standard Model is minimally extended by two quasi-degenerate sterile fermions. We also discuss the possibility of exploring the latter case searching for double-kinks in KATRIN.

  • Lepton Masses and Mixing from Modular $S_4$ Symmetry
    SISSA 25/2018/FISI
    Nucl.Phys. B939 (2019) 292-307

    by: Penedo, J.T. (INFN, Trieste) et al.

    We study models of lepton masses and mixing based on broken modular invariance. We consider invariance under the finite modular group $\Gamma_4 \simeq S_4$ and focus on the minimal scenario where the expectation value of the modulus is the only source of symmetry breaking, such that no flavons need to be introduced. After constructing a basis for the lowest weight modular forms, we build two minimal models, one of which successfully accommodates charged lepton masses and neutrino oscillation data, while predicting the values of the Dirac and Majorana CPV phases.

  • Linear seesaw for Dirac neutrinos with $A_4$ flavour symmetry
    Phys.Lett. B789 (2019) 59-70

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

    We propose a linear seesaw model to realise light Dirac neutrinos within the framework of $A_4$ discrete flavour symmetry. The additional fields and their transformations under the flavour symmetries are chosen in such a way that naturally predicts the hierarchies of different elements of the seesaw mass matrix and also keeps the unwanted terms away. For generic choices of flavon alignments, the model predicts normal hierarchical light neutrino masses with the atmospheric mixing angle in the lower octant. Apart from predicting interesting correlations between different neutrino parameters as well as between neutrino and model parameters, the model also predicts the leptonic Dirac CP phase to lie in a specific range $-\pi/2\lesssim \delta \lesssim -\pi/5$ and $\pi/5\lesssim \delta \lesssim \pi/2$ that includes the currently preferred maximal value. The predictions for the absolute neutrino masses in one specific version of the model can also saturate the cosmological upper bound on sum of absolute neutrino masses.

  • Statistical Significance of CP Violation in Long Baseline Neutrino Experiments
    Nucl.Instrum.Meth. A921 (2019) 71-80

    by: Toki, Walter (Colorado State U.) et al.

    The p-value or statistical significance of a CP conservation null hypothesis test is determined from counting electron neutrino and antineutrino appearance oscillation events. The statistical estimates include cases with background events and different data sample sizes, graphical plots to interpret results and methods to combine p-values from different experiments. These estimates are useful for optimizing the search for CP violation with different amounts of neutrino and antineutrino beam running, comparing results from different experiments and for simple cross checks of more elaborate statistical estimates that use likelihood fitting of neutrino parameters.

  • Scientific Works of Shoichi Sakata and Commentaries

    by: Maskawa, Toshihide (Nagoya U.)

  • Study Standard Model and Majorana Neutrino Contributions to $B^{+} \to K^{(*)\pm}\mu^+\mu^{\mp}$
    Chin.Phys. C43 (2019) 023101

    by: Li, Hong-lei (Jinan U., Jinan) et al.

    Lepton number violation processes can be induced by the Majorana neutrino exchange, which provide evidence for the Majorana nature of neutrinos. In addition to the natural explanation of the small neutrino masses, Type-I seesaw mechanism predicts the existence of Majorana neutrinos. The aim of this work is to study the B meson rare decays $B^{+} \to K^{(*)+}\mu^+\mu^-$ in the standard model and its extensions, and then to investigate the same-sign decay processes $B^{+}\to K^{(*)-}\mu^{+}\mu^+$. The corresponding dilepton invariant mass distributions are predicted. It is found that the dilepton angular distributions illustrate the properties of new interactions induced by the Majorana neutrinos.

  • Assessing Perturbativity and Vacuum Stability in High-Scale Leptogenesis
    JHEP 1812 (2018) 111

    by: Ipek, Seyda (UC, Irvine) et al.

    We consider the requirements that all coupling constants remain perturbative and the electroweak vacuum metastable up to the Planck scale in high-scale thermal leptogenesis, in the context of a type-I seesaw mechanism. We find a large region of the model parameter space that satisfies these conditions in combination with producing the baryon asymmetry of the Universe. We demonstrate these conditions require Tr[Y$_{N}^{†}$ Y$_{N}$] ≲ 0.66 on the neutrino Yukawa matrix. We also investigate this scenario in the presence of a large number N$_{F}$ of coloured Majorana octet fermions in order to make quantum chromodynamics asymptotically safe in the ultraviolet.

  • Exploring the intrinsic Lorentz-violating parameters at DUNE
    Phys.Lett. B788 (2019) 308-315

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

    Neutrinos can push our search for new physics to a whole new level. What makes them so hard to be detected, what allows them to travel humongous distances without being stopped or deflected allows to amplify Planck suppressed effects (or effects of comparable size) to the level we can measure or bound in DUNE. In this work we analyse the sensitivity of DUNE to CPT and Lorentz--violating interactions in a framework that allows a straightforward extrapolation of the bounds obtained to any phenomenological modification of the dispersion relation of neutrinos.

  • Neutrino and Collider Implications of a Left-Right Extended Zee Model
    Phys.Rev. D98 (2018) 115038

    by: Khan, Sarif (Harish-Chandra Res. Inst.) et al.

    We study a simple left-right symmetric (LRS) extension of the Zee model for neutrino mass generation. An extra $SU(2)_{L/R}$ singlet charged scalar helps in generating a loop-induced Majorana mass for neutrinos in this model. The right-handed neutrinos in this case are very light of the order of a few eV to a few MeV which makes this scenario quite different from other LRS models. We have analyzed the scalar potential and Higgs spectrum in detail, which also play an important role for the neutrino phenomenology. We identified the parameter regions in the model which satisfy the experimentally observed neutrino masses and mixings along with other experimental constraints. We have then studied the collider signatures of the charged scalar at $e^+e^-$ colliders with different benchmark points. It is possible to get a huge enhancement in the production cross-section of the charged scalar at lepton collider compared to the hadron colliders, resulting in a much stronger signal which can be easily observed at the upcoming ILC or CLIC experiments.

  • NNLOPS accurate predictions for $W^+W^-$ production
    JHEP 1812 (2018) 121

    by: Re, Emanuele (CERN) et al.

    We present novel predictions for the production of $W^+W^-$ pairs in hadron collisions that are next-to-next-to-leading order accurate and consistently matched to a parton shower (NNLOPS). All diagrams that lead to the process $pp\to e^- \bar \nu_e\;\mu^+\nu_\mu+X$ are taken into account, thereby including spin correlations and off-shell effects. For the first time full NNLOPS accuracy is achieved for a $2\to 4$ process. We find good agreement, at the 1$\sigma$ level, with the $W^+W^-$ rates measured by ATLAS and CMS. The importance of NNLOPS predictions is evident from differential distributions sensitive to soft-gluon effects and from the large impact ($10$% and more) of including next-to-next-to-leading order corrections on top of MiNLO. We define a charge asymmetry for the $W$ bosons and the leptons in $W^+W^-$ production at the LHC, which is sensitive to the $W$ polarizations and hence can be used as a probe of new physics.

  • Unparticle Decay of Neutrinos and its Possible Signatures at a ${\rm Km}^2$ Detector for (3+1) Flavour Framework
    JHEP 1901 (2019) 066

    by: Pandey, Madhurima (Saha Inst.)

    We consider a scenario where ultra high energy neutrinos undergo unparticle decay during its passage from its cosmological source to Earth. The idea of unparticle had been first proposed by Georgi by considering the possible existence of an unknown scale invariant sector at high energies and the unparticles in this sector manifest itself below a dimensional transmutation scale $\Lambda_{\cal U}$. We then explore the possible signature of such decaying neutrinos to unparticles at a square kilometer detector such as IceCube.

  • CPT-Symmetric Universe
    Phys.Rev.Lett. 121 (2018) 251301

    by: Boyle, Latham (Perimeter Inst. Theor. Phys.) et al.

    We propose that the state of the universe does {\it not} spontaneously violate CPT. Instead, the universe after the big bang is the CPT image of the universe before it, both classically and quantum mechanically. The pre- and post-bang epochs comprise a universe/anti-universe pair, emerging from nothing directly into a hot, radiation-dominated era. CPT symmetry selects a unique QFT vacuum state on such a spacetime, providing a new interpretation of the cosmological baryon asymmetry, as well as a remarkably economical explanation for the cosmological dark matter. Requiring only the standard three-generation model of particle physics (with right-handed neutrinos), a $\mathbb{Z}_2$ symmetry suffices to render one of the right-handed neutrinos stable. We calculate its abundance from first principles: matching the observed dark matter density requires its mass to be $4.8\times10^{8}~{\rm GeV}$. Several other testable predictions follow: (i) the three light neutrinos are Majorana and allow neutrinoless double $\beta$ decay; (ii) the lightest neutrino is massless; and (iii) there are no primordial long-wavelength gravitational waves. We mention connections to the strong CP problem and the arrow of time.

  • New physics searches in nuclear and neutron $\beta$ decay
    Prog.Part.Nucl.Phys. 104 (2019) 165-223

    by: Gonzalez-Alonso, Martin (CERN) et al.

    The status of tests of the standard electroweak model and of searches for new physics in allowed nuclear β decay and neutron decay is reviewed including both theoretical and experimental developments. The sensitivity and complementarity of recent and ongoing experiments are discussed with emphasis on their potential to look for new physics. Measurements are interpreted using a model-independent effective field theory approach enabling to recast the outcome of the analysis in many specific new physics models. Special attention is given to the connection that this approach establishes with high-energy physics. A new global fit of available β -decay data is performed incorporating, for the first time in a consistent way, superallowed 0+→0+ transitions, neutron decay and nuclear decays. The constraints on exotic scalar and tensor couplings involving left- or right-handed neutrinos are determined while a constraint on the pseudoscalar coupling from neutron decay data is obtained for the first time as well. The values of the vector and axial–vector couplings, which are associated within the standard model to Vud and gA respectively, are also updated. The ratio between the axial and vector couplings obtained from the fit under standard model assumptions is CA∕CV=−1.27510(66) . The relevance of the various experimental inputs and error sources is critically discussed and the impact of ongoing measurements is studied. The complementarity of the obtained bounds with other low- and high-energy probes is presented including ongoing searches at the Large Hadron Collider.

  • Neutrino tomography of the Earth
    Nature Phys. 15 (2019) 37-40

    by: Donini, Andrea (Valencia U., IFIC) et al.

    Cosmic-ray interactions with the nuclei of the Earth's atmosphere produce a flux of neutrinos in all directions with energies extending above the TeV scale. However, the Earth is not a fully transparent medium for neutrinos with energies above a few TeV. At these energies, the charged-current neutrino-nucleon cross section is large enough so that the neutrino mean-free path in a medium with the Earth's density is comparable to the Earth's diameter. Therefore, when neutrinos of these energies cross the Earth, there is a non-negligible probability for them to be absorbed. Since this effect depends on the distance traveled by neutrinos and on their energy, studying the zenith and energy distributions of TeV atmospheric neutrinos passing through the Earth offers an opportunity to infer the Earth's density profile. Here we perform an Earth tomography with neutrinos using actual data, the publicly available one-year through-going muon sample of the atmospheric neutrino data of the IceCube neutrino telescope. We are able to determine the mass of the Earth, its moment of inertia, the mass of the Earth's core and to establish the core is denser than the mantle, using weak interactions only, in a way completely independent from gravitational measurements. Our results confirm that this can be achieved with current neutrino detectors. This method to study the Earth's internal structure, complementary to the traditional one from geophysics based on seismological data, is starting to provide useful information and it could become competitive as soon as more statistics is available thanks to the current and larger future neutrino detectors.

  • Beta equilibrium in neutron star mergers
    Phys.Rev. C98 (2018) 065806

    by: Alford, Mark G. (Washington U., St. Louis) et al.

    We show that the commonly used criterion for beta equilibrium in neutrino-transparent dense nuclear matter becomes invalid as temperatures rise above 1 MeV. Such temperatures are attained in neutron star mergers. By numerically computing the relevant weak interaction rates we find that the correct criterion for beta equilibrium requires an isospin chemical potential that can be as large as 10-20 MeV, depending on the temperature at which neutrinos become trapped.

  • Scale-dependent galaxy bias, CMB lensing-galaxy cross-correlation, and neutrino masses
    Phys.Rev. D98 (2018) 123526

    by: Giusarma, Elena (LBL, Berkeley) et al.

    One of the most powerful cosmological datasets when it comes to constraining neutrino masses is represented by galaxy power spectrum measurements, $P_{gg}(k)$. The constraining power of $P_{gg}(k)$ is however severely limited by uncertainties in the modeling of the scale-dependent galaxy bias $b(k)$. In this Letter we present a new method to constrain $b(k)$ by using the cross-correlation between the Cosmic Microwave Background (CMB) lensing signal and galaxy maps ($C_\ell^{\rm \kappa g}$) using a simple but theoretically well-motivated parametrization for $b(k)$. We apply the method using $C_\ell^{\rm \kappa g}$ measured by cross-correlating Planck lensing maps and the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 (DR11) CMASS galaxy sample, and $P_{gg}(k)$ measured from the BOSS DR12 CMASS sample. We detect a non-zero scale-dependence at moderate significance, which suggests that a proper modeling of $b(k)$ is necessary in order to reduce the impact of non-linearities and minimize the corresponding systematics. The accomplished increase in constraining power of $P_{gg}(k)$ is demonstrated by determining a 95% C.L. upper bound on the sum of the three active neutrino masses $M_{\nu}$ of $M_{\nu}<0.19\, {\rm eV}$. This limit represents a significant improvement over previous bounds with comparable datasets. Our method will prove especially powerful and important as future large-scale structure surveys will overlap more significantly with the CMB lensing kernel providing a large cross-correlation signal.

  • Precision Physics at LEP

    by: Bethke, Siegfried (Munich, Max Planck Inst.)

    As a part of the homage on Guido Altarelli, summarised in the book "From my vast repertoire - the legacy of Guido Altarelli" edited by S. Forte, A. Levy and G. Ridolfi, this contribution collects some of the technological and scientific highlights of precision physics at LEP, the Large Electron-Positron collider operated, from 1989 to 2000, at the European Laboratory for Particle Physics, CERN.

  • Search for sterile neutrinos in a universe of vacuum energy interacting with cold dark matter
    Phys.Dark Univ. 100261
    Phys.Dark Univ. 23 (2019) 100261

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

    We investigate the cosmological constraints on sterile neutrinos in a universe in which vacuum energy interacts with cold dark matter by using latest observational data. We focus on two specific interaction models, Q=βHρv and Q=βHρc . To overcome the problem of large-scale instability in the interacting dark energy scenario, we employ the parametrized post-Friedmann (PPF) approach for interacting dark energy to do the calculation of perturbation evolution. The observational data sets used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation measurements, the type-Ia supernova data, the Hubble constant direct measurement, the galaxy weak lensing data, the redshift space distortion data, and the Planck lensing data. Using the all-data combination, we obtain Neff<3.522 and mν,sterileeff<0.576eV for the Q=βHρv model, and Neff=3.204−0.135+0.049 and mν,sterileeff=0.410−0.330+0.150eV for the Q=βHρc model. The latter indicates ΔNeff>0 at the 1.17 σ level and a nonzero mass of sterile neutrino at the 1.24 σ level. In addition, for the Q=βHρv model, we find that β=0 is consistent with the current data, and for the Q=βHρc model, we find that β>0 is obtained at more than 1 σ level.

  • Scalar Quintuplet Minimal Dark Matter with Yukawa Interactions: Perturbative up to the Planck Scale
    Chin.Phys. C43 (2019) 023102

    by: Cai, Chengfeng (SYSU, Guangzhou) et al.

    We confront the perturbativity problem in the real scalar quintuplet minimal dark matter model. In the original model, the quintuplet quartic self-coupling inevitably hits a Landau pole at a scale $\sim 10^{14}$ GeV, far below the Planck scale. In order to push up this Landau pole scale, we extend the model with a fermionic quintuplet and three fermionic singlets which couple to the scalar quintuplet via Yukawa interactions. Involving such Yukawa interactions at a scale $\sim 10^{10}$ GeV can not only keep all couplings perturbative up to the Planck scale, but can also explain the smallness of neutrino masses via the type-I seesaw mechanism. Furthermore, we identify the parameter regions favored by the condition that perturbativity and vacuum stability are both maintained up to the Planck scale.

  • Neutrino-Oxygen CC0$\pi$ scattering in the SuSAv2-MEC model
    J.Phys. G46 (2019) 015104

    by: Megias, G.D. (Seville U.) et al.

    We present the predictions of the SuSAv2-MEC model for the double differential charged-current muonic neutrino (antineutrino) cross section on water for the T2K neutrino (antineutrino) beam. We validate our model by comparing with the available inclusive electron scattering data on oxygen and compare our predictions with the recent T2K $\nu_\mu$-$^{16}$O data, finding good agreement at all kinematics. We show that the results are very similar to those obtained for $\nu_\mu-^{12}$C scattering, except at low energies, and we comment on the origin of this difference. A factorized spectral function model of $^{16}$O is also included for purposes of comparison.

  • Matter Parity Violating Dark Matter Decay in Minimal SO(10), Unification, Vacuum Stability and Verifiable Proton Decay
    Nucl.Phys. B938 (2019) 56-113

    by: Sahoo, Biswonath (Siksha O Anusandhan U., Bhubaneswar) et al.

    In direct breaking of non-supersymmetric SO(10) to the standard model, we investigate the possibility that dark matter (DM) decaying through its mixing with right-handed neutrino (RH$\nu$) produces high energy IceCube neutrinos having type-I seesaw masses. Instead of one universal mixing and one common heavy RH$\nu$ mass proposed in a recent standard model extension, we find that underlying quark-lepton symmetry resulting in naturally hierarchical RH$\nu$ masses predict a separate mixing with each of them. We determine these mixings from the seesaw prediction of the DM decay rates into the light neutrino flavors. We further show that these mixings originate from Planck-scale assisted spontaneously broken matter parity needed to resolve the associated cosmological domain wall problem. This leads to the prediction of a new LHC accessible matter-parity odd Higgs scalar which also completes vacuum stability in the Higgs potential for its mass $M_{\chi_S}\simeq 178$ GeV. Two separate minimal SO(10) models are further noted to predict such dark matter dynamics where a single scalar submultiplet from ${126}^{\dagger}_H$ or ${210}_H$ of intermediate mass achieves precision gauge coupling unification. Despite the presence of two large Higgs representations and the fermionic dark matter host, ${45}_F$, experimentally accessible proton lifetimes are also predicted with reduced uncertainties.

  • Are neutrino masses modular forms?

    by: Feruglio, Ferruccio (INFN, Padua)

    We explore a new class of supersymmetric models for lepton masses and mixing angles where the role of flavour symmetry is played by modular invariance. The building blocks are modular forms of level N and matter supermultiplets, both transforming in representations of a finite discrete group Gamma_N. In the simplest version of these models, Yukawa couplings are just modular forms and the only source of flavour symmetry breaking is the vacuum expectation value of a single complex field, the modulus. In the special case where modular forms are constant functions the whole construction collapses to a supersymmetric flavour model invariant under Gamma_N, the case treated so far in the literature. The framework has a number of appealing features. Flavon fields other than the modulus might not be needed. Neutrino masses and mixing angles are simultaneously constrained by the modular symmetry. As long as supersymmetry is exact, modular invariance determines all higher-dimensional operators in the superpotential. We discuss the general framework and we provide complete examples of the new construction. The most economical model predicts neutrino mass ratios, lepton mixing angles, Dirac and Majorana phases uniquely in terms of the modulus vacuum expectation value, with all the parameters except one within the experimentally allowed range. As a byproduct of the general formalism we extend the notion of non-linearly realised symmetries to the discrete case.

  • Neutrinoless double beta decay in minimal left-right symmetric model with universal seesaw
    Int.J.Mod.Phys. A33 (2018) 1850198

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

    We present a detailed discussion on neutrinoless double beta decay (0νββ) within left–right symmetric models based on the gauge symmetry of type SU(2)L × SU(2)R × U(1)B−L as well as SU(3)L × SU(3)R × U(1)X where fermion masses including that of neutrinos are generated through a universal seesaw mechanism. We find that one or more of the right-handed neutrinos could be as light as a few keV if left–right symmetry breaking occurs in the range of a few TeV to 100 TeV. With such light right-handed neutrinos, we perform a detailed study of new physics contributions to 0νββ and constrain the model parameters from the latest experimental bound on such a rare decay process. We find that the new physics contribution to 0νββ in such a scenario, particularly the heavy–light neutrino mixing diagrams, can individually saturate the existing experimental bounds, but their contributions to total 0νββ half-life cancel each other due to unitarity of the total 6 × 6 mass matrix. The effective contribution to half-life therefore, arises from the purely left and purely right neutrino and gauge boson mediated diagrams. We find that the parameter space saturating the 0νββ bounds remains allowed from the latest experimental bounds on charged lepton flavor violating decays like μ → eγ. We finally include the bounds from cosmology and supernova to constrain the parameter space of the model.

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