
Semileptonic and nonleptonic decays of $D$ into tensor mesons with lightcone sum rule
arXiv:1901.03873 Phys.Rev. D99 (2019) 013001
by: Momeni, S. (Isfahan Tech. U.) et al.
Abstract: Form factors of D decays into JPC=2++ tensor mesons are calculated in the lightcone sum rules approach up to twist4 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 twoparticle distribution amplitude ⟨Tq¯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 105, and the nonleptonic ones show better agreement with the experimental data in comparison to the IsgurScoraGrinsteinWise predictions.

Neutralcurrent weak pion production off the nucleon in covariant chiral perturbation theory
arXiv:1901.00773
by: Yao, DeLiang Abstract: 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 nonresonant contribution, which is not present in event generators of broad use in neutrino oscillation and cross section experiments such as GENIE and NuWro.

Spinflavor oscillations of Dirac neutrinos in matter under the influence of a plane electromagnetic wave
arXiv:1901.01022
by: Dvornikov, Maxim Abstract: We study oscillations of Dirac neutrinos in background matter and a plane electromagnetic wave. We find the new exact solution of the DiracPauli 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 spinflavor 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 spinflavor 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?
arXiv:1901.01205
by: Krishnan, R. Abstract: 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
arXiv:1901.01170
by: Dhargyal, Lobsang Abstract: 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 (g2) by BNL. We had shown that all these anomalies as well as Baryongenesis, Darkmatter and small neutrino masses could be explained by introducing new exotic scalars, leptons and scalarleptoquarks 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 HLLHC or with even better chance of observing these signatures are in the upcoming precision machines such as ILC, CEPC etc.

Doublebeta decay and its potential to explore beyond standard model physics
Int.J.Mod.Phys. A33 (2018) 1845012
by: Stoica, Sabin (Bucharest, IFINHH)
Abstract: Doublebeta 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 doublebeta (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 Majoranalike 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 halflives formulas, for different decay modes, transitions and mechanisms of occurrence. Reliable computations of these quantities may result in reliable predictions of DBD halflives 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 axialvector constant.

Spinorvector duality and sterile neutrinos in string derived models
LTH 1192 arXiv:1812.10562
by: Faraggi, Alon E. (Liverpool U., Dept. Math.)
Abstract: The MiniBooNE collaboration found evidence for the existence of sterile neutrinos, at a mass scale comparable to the active lefthanded neutrinos. While sterile neutrinos arise naturally in large volume string scenarios, they are more difficult to accommodate in heteroticstring derived models that reproduce the GUT embedding of the Standard Model particles. Sterile neutrinos in heteroticstring 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 spinorvector duality to guarantee that the extra $U(1)_{Z^\prime}$ symmetry can remain unbroken down to low scales.

Lowscale Leptogenesis with Minimal Lepton Flavour Violation
arXiv:1812.11964
by: Dolan, Matthew J. (ARC, CoEPP, Melbourne) et al.
Abstract: We analyse the feasibility of lowscale 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, MLFVISS leptogenesis succeeds only with a highly tuned choice of Majorana masses. For MLFVLSS, 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 lowenergy flavour violation experiments, in particular $\mu \rightarrow e\,\gamma$. We find that the future MEGII experiment, while sensitive to MLFV in our setup, will not be sensitive to the specific regions required for resonant leptogenesis.

PecceiQuinn Symmetry and Nucleon Decay in Renormalizable SUSY SO(10)
arXiv:1812.11695 OSUHEP1808
by: Babu, K.S. Abstract: We suggest simple ways of implementing PecceiQuinn (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 $\mue$ conversion in nuclei, induced by the Dirac neutrino Yukawa couplings, are found to be within reach of forthcoming experiments.

Neutrino, parity violaton, VA: a historical survey
arXiv:1812.11629
by: Hadjiivanov, Ludmil (Sofiya, Inst. Nucl. Res.)
Abstract: 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
arXiv:1812.11570
by: Pandey, Madhurima (Saha Inst.)
Abstract: 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 4flavour neutrino scenario (3 active + 1 sterile) with both massflavour 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 quarkgluon string model
arXiv:1812.11341 Preprint of JINR P220184 Dubna
by: Sinegovsky, S.I. (Dubna, JINR) et al.
Abstract: We calculate the atmospheric flux of prompt neutrinos, produced in decays of the charmed particles at energies beyond 1 TeV. Cross sections of the Dmesons and ${\Lambda}^{+}_{c}$ baryons production in pA and $\pi$A collisions are calculated in the phenomenological quarkgluon 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
arXiv:1812.11289 SISSA 57/2018/FISI IPMU180209
by: Novichkov, P.P. (INFN, Trieste) et al.
Abstract: 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 masssquared 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.

Superweak force and neutrino masses
arXiv:1812.11189
by: Trócsányi, Zoltán (Eotvos U.)
Abstract: 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 Zcharges 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 righthanded 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 antimuon 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
arXiv:1812.11931 OUHEP994
by: Das, Arindam Abstract: We consider a gauged U(1)$_{BL}$ (BaryonminusLepton number) extension of the Standard Model (SM), which is anomalyfree in the presence of three RightHanded Neutrinos (RHNs). Associated with the U(1)$_{BL}$ 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)$_{BL}$ 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) Run2 and its production cross section is already severely constrained. The constraint will become more stringent by the future experiments with the HighLuminosity upgrade of the LHC (HLLHC). We find a possibility that even after a null $Z^\prime$ boson search result at the HLLHC, the 250 GeV ILC can search for the RHN pair production through the final state with samesign dileptons plus jets, which is a `smokinggun' signature from the Majorana nature of RHNs. In addition, some of RHNs are longlived 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
arXiv:1812.11362
by: Blondel, Alain Abstract: 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 $\nu_{\tau}$, isospin partner of the tau lepton, was definitely established in 19811986; 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 TeVscale and neutrinoless double beta decay
arXiv:1812.11323
by: Asaka, Takehiko Abstract: We investigate a resonant leptogenesis scenario by quasidegenerate righthanded neutrinos which have TeVscale masses. Especially, we consider the case when two righthanded 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 righthanded 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
arXiv:1812.11072 EPHOU18017 HUPD1810
by: Kobayashi, Tatsuo (Hokkaido U.) et al.
Abstract: 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
arXiv:1812.11154
by: Chacko, Zackaria (Maryland U.) et al.
Abstract: 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 pseudoNambu 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 gramyears 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.

Singletdoublet fermion and triplet scalar dark matter with radiative neutrino masses
arXiv:1812.11133 MSTP1833
by: Fiaschi, Juri (Munster U., ITP) et al.
Abstract: We present a detailed study of a combined singletdoublet 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 flavormass majorization uncertainty relations and their links to the mixing matrix
arXiv:1812.10973
by: Rastegin, Alexey E. (Irkutsk State U.)
Abstract: 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 PontecorvoMakiNakagawaSakata (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 entanglementassisted studying parameters of threeflavor neutrino oscillations.

On $\theta_{23}$ Octant Measurement in $3+1$ Neutrino Oscillations in T2HKK
arXiv:1812.10940
by: Haba, Naoyuki (Shimane U.) et al.
Abstract: It has been pointed out that the mixing of an eVscale 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 activesterile 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 TokaitoHyperKamiokandetoKorea (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 sterileactive 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 typeII seesaw mechanism into the 331 model
arXiv:1812.10570
by: de Sousa Pires, Carlos Antônio (Paraiba U.) et al.
Abstract: 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 subeV 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 331 model with righthanded neutrinos. Interestingly, we propose the mechanism which provides small masses to both the standard neutrinos as well as to the righthanded 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 quasielastic neutrino chargedcurrent and twobody meson exchange current models with the MiniBooNE neutrino data and analysis of these processes at energies available at the NOvA experiment
arXiv:1812.11073
by: Butkevich, A.V. Abstract: The chargedcurrent quasielastic (CCQE) scattering of muon neutrinos on a carbon target is analyzed using the relativistic distortedwave impulse approximation (RDWIA) taking into account the contribution of the twoparticle and twohole meson exchange current ($2p2h$ 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 fluxintegrated CCQElike 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
arXiv:1812.10268 J.Phys. G46 (2019) 015001
by: Channey, Kanwaljeet S. (Delhi U.) et al.
Abstract: The TriBimaximal (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
arXiv:1812.09828
by: Błaut, A. (Wroclaw U.) et al.
Abstract: 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 nonvanishing transversal components of $\nu_e$ spin polarization may appear, both Teven and Todd. $\nu_e$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 nonstandard $V + A$, 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 leftright 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 nonvanishing interference between $VA$ and $V+A$ interactions, proportional to the Teven longitudinal $\nu_e$ polarization. Our modelindependent study is carried out for the flavor $\nu_e$ eigenstates in the relativistic $\nu_e$ limit.

Neutrino oscillations in accelerated frames
arXiv:1812.09697 EPL 124 (2018) 51001
by: Blasone, Massimo (Salerno U.) et al.
Abstract: 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 twoflavor 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 Nonthermal Moduli Cosmology
arXiv:1812.09341
by: Chen, MuChun (UC, Irvine) et al.
Abstract: The appearance of scalar/moduli fields in the early universe, as motivated by string theory, naturally leads to nonthermal "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 stringinspired components (e.g. supersymmetry, discrete symmetries, GreenSchwarz 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 overlyrapid proton decay due to dimension4,5 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 gravitationalgauge 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
arXiv:1812.09325
by: Bramante, Joseph (Queen's U., Kingston) et al.
Abstract: We show that dark matter with a pernucleon 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 spinindependent and spindependent 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) QCDcharged dark matter, and (3) a recently proposed model of Planckmass baryoncharged 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
arXiv:1812.10290
by: Masud, Mehedi (Valencia U., IFIC) et al.
Abstract: 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 subdominant 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 twodimensional space of parameters considered.

Ultrahighenergy cosmicray nuclei and neutrinos from enginedriven supernovae
arXiv:1812.10289
by: Zhang, B. Theodore (Peking U., Beijing) et al.
Abstract: Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahighenergy 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 corecollapse supernova rate, the observed UHECR spectrum and composition can be explained with the total cosmicray 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 0.11 EeV range, satisfying nucleussurvival bounds. The associated cosmogenic neutrino flux is calculated, and shown to be comparable to the source neutrino flux. These ultrahighenergy neutrinos can be detected by ultimate detectors such as the Giant Radio Askaryan Neutrino Detector and Probe Of Extreme MultiMessenger Astrophysics.

Linear seesaw model with hidden $SU(2)_H \times U(1)_X$ gauge symmetry
arXiv:1812.08473 KIASP18117 APCTP Pre2018  018
by: Nomura, Takaaki (Korea Inst. Advanced Study, Seoul) et al.
Abstract: 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
arXiv:1812.08768 IPPP/18/113/FERMILABPUB18686ANDPPDT
by: Argüelles, Carlos A. (MIT, Cambridge, Dept. Phys.) et al.
Abstract: 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 CHARMII, can probe this class of models. We argue that by using sideband measurements of neutrinoelectron 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 neutrinoelectron 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 neutrinonucleus cross sections in the search for new physics in neutrino experiments.

Neutrino spin oscillations in polarized matter
arXiv:1812.08635
by: Grigoriev, A. (Moscow, MIPT) et al.
Abstract: 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
arXiv:1812.08750 CP31877 IPPP/18/111 PITTPACC1821
by: Pascoli, Silvia (Durham U., IPPP) et al.
Abstract: 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 longstandard search strategy for heavy $N$ decaying to multiple charged leptons $(\ell)$, $pp \to N\ell X \to 3\ell \nu X$. For electroweak and TeVscale $N$, we propose a qualitatively new collider analysis premised on a dynamic jet veto and discriminating, on an eventbyevent 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 activesterile 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 detectorspecific tuning and application of multivariant / machines learning techniques.

Assessing the sensitivity of PINGU to effective dark matternucleon interactions
arXiv:1812.08270
by: Bäckström, Anton (Chalmers U. Tech.) et al.
Abstract: We calculate the sensitivity of next generation neutrino telescopes to the 28 (isoscalar and isovector) coupling constants defining the nonrelativistic 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 DMmass  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 spinindependent and spindependent DMnucleon interactions, but also velocitydependent or momentumdependent interactions that generate coherently enhanced DMnucleus 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 DMnucleon interaction and for all DM masses tested here. When DM primarily annihilates into $\tau\bar{\tau}$, a PINGUlike detector will improve upon current exclusion limits for DM masses below $35$ GeV, independently of the assumed DMnucleon interaction.

Natural Seesaw and Leptogenesis from Hybrid of HighScale Type I and TeVScale Inverse
arXiv:1812.08204
by: Agashe, Kaustubh (Maryland U.) et al.
Abstract: 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 TeVscale 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 quasidegeneracy 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 highscale ($M_N\gg$ 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 NoScale Flipped SU(5)
arXiv:1812.08184 KCLPHTH201877 CERNTH2018273 UT1829 ACT0518 MITH1815 UMNTH380818 FTPIMINN1823
by: Ellis, John (King's Coll. London) et al.
Abstract: Noscale supergravity and the flipped SU(5)$\times$U(1) gauge group provide an ambitious prototype stringinspired scenario for physics below the string scale, which can accommodate the Starobinskylike 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
arXiv:1812.08650
by: Albert, A. (Strasbourg, IPHC) et al.
Abstract: 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 bestfit values  and constraints on the 3+1 neutrino model have been derived.

Scalar NonStandard Interactions in Neutrino Oscillation
arXiv:1812.08376 IPMU180206 FERMILABPUB18487T
by: Ge, ShaoFeng (Tokyo U., IPMU) et al.
Abstract: 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
arXiv:1812.08178
by: McKeen, David (TRIUMF)
Abstract: We investigate the possibility that particles that are longlived 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 PTOLEMYlike experiment given current cosmological constraints.

Oneloop neutrino mass model with $SU(2)_L$ multiplet fields
arXiv:1812.08016 KIASP18115 APCTP Pre2018  017
by: Nomura, Takaaki (Korea Inst. Advanced Study, Seoul) et al.
Abstract: We propose a oneloop neutrino mass model with several $SU(2)_L$ multiplet fermions and scalar fields in which the inert feature of a scalar to realize the oneloop neutrino mass can be achieved by the cancellation among Higgs couplings thanks to nontrivial terms in the Higgs potential. Then we discuss our typical cutoff 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 HLLHC and HELHC
arXiv:1812.07831 CERNLPCC201805 FERMILABPUB18694CMST
by: Cid Vidal , X. (Santiago de Compostela U., IGFAE) et al.
Abstract: This is the third out of five chapters of the final report [1] of the Workshop on Physics at HLLHC, and perspectives on HELHC [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 centreofmass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as $15$ ab$^{1}$ of data at a centreofmass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more modeldependent 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, axionlike particles, heavy scalars, vectorlike quarks, and more. Particular attention is placed, especially in the study of the HLLHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HLLHC, on top of allowing to extend the present LHC mass and coupling reach by $2050\%$ on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HLLHC, the reach in most observables will, generally more than double at the HELHC, which may represent a good candidate future facility for a final test of TeVscale new physics.

Machine learning classification: case of Higgs boson CP state in H to tau tau$ decay at LHC
arXiv:1812.08140 IFJPANIV201820
by: Lasocha, K. (Jagiellonian U.) et al.
Abstract: 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 multidimensional phasespace. 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 4momenta 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 highlevel 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
arXiv:1812.07720
by: Di Bari, Pasquale (Southampton U.) et al.
Abstract: 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 righthanded 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
arXiv:1812.07823
by: Alikhanov, I. (Moscow, INR)
Abstract: 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 neutrinoinduced reactions at $e^+e^$ and $ep$ colliders as well as at other lepton colliding facilities. We give two examples of its application to electronpositron collisions.

Angular and CPviolation analyses of $\bar{B}\to D^{*+} l^\bar{\nu}_{l}$ decays at hadron collider experiments
arXiv:1812.08144
by: Marangotto, Daniele (INFN, Milan)
Abstract: 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 CPviolating observables by exploiting approximate reconstruction algorithms using information from detectable finalstate 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 CPviolating 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 highintensity observables
arXiv:1812.08062 LPTOrsay1886 Front.in Phys. 6 (2018) 142
by: Abada, Asmaa (Orsay, LPT) et al.
Abstract: 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 nonnegligible mixings to the active (light) neutrinos, and if they are not excessively heavy, one expects important contributions to numerous highintensity 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
arXiv:1812.07426 Phys.Rev. D99 (2019) 023008
by: Lopes, Ilídio (Lisbon, CENTRA) et al.
Abstract: The next generation of solar neutrino detectors will provide a precision measure of the $^8$B electronneutrino spectrum in the energy range from 115 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 electronneutrino 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 electronneutrino 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 331 model with type I and II seesaw mechanisms
arXiv:1812.07263 Mod.Phys.Lett. A34 (2019) 1950005
by: Vien, V.V. (Duy Tan U.) et al.
Abstract: 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 righthanded 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 ElectronProton Colliders
arXiv:1812.07187
by: Ari, V. (Ankara U.) et al.
Abstract: The Large Hadron Electron Collider and the Future Circular Colliderhadron electron with high centerofmass energy and luminosity allow to better understand the Standard Model and to examine new physics beyond the Standard Model in the electroweak sector. Multiboson processes permit for a measurement of the gauge boson selfinteractions 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 centerofmass energies of 1.30, 1.98 TeV and at the Future Circular Colliderhadron electron with centerofmass 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 dimension8 operators.

Neutrinoless Double Beta Decay and Light Sterile Neutrino
arXiv:1811.09957 J.Korean Phys.Soc. 73 (2018) 16251630
by: Jang, C.H. (ChungAng U.) et al.
Abstract: 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 threeneutrino 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 shortbaseline 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 LowEnergy NeutrinoNucleus Interactions
arXiv:1811.08533 Phys.Rev. C98 (2018) 065505
by: Hayes, A.C. Abstract: We examine the importance of conserving the vector current in calculating lowenergy neutrinonucleus 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 normalparity nonspinflip 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
arXiv:1811.02895 TTP18038 NCTSPH1816 JHEP 1901 (2019) 005
by: Deppisch, Thomas (KIT, Karlsruhe, TTP) et al.
Abstract: 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
arXiv:1811.02295 RIKENiTHEMSReport18 Phys.Lett. B789 (2019) 7681
by: Fujikawa, Kazuo (Wako, RIKEN)
Abstract: We discuss a generalization of the PauliGursey transformation, which is motivated by the AutonneTakagi 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 PauliGursey 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 PauliGursey 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 Diractype fermions appear with welldefined C, P and CP, and thus the C symmetry for Majorana neutrinos agrees with the C symmetry for Diractype fermions. This fully symmetric setting corresponds to the idea of Majorana neutrinos as Bogoliubov quasiparticles. In contrast, the conventional direct construction of Majorana neutrinos in the seesaw model, where CP is welldefined 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.

Timevarying neutrino mass from a supercooled phase transition: current cosmological constraints and impact on the $\Omega_m$$\sigma_8$ plane
arXiv:1811.01991 Phys.Rev. D99 (2019) 023501
by: Lorenz, Christiane S. (Oxford U.) et al.
Abstract: In this paper we investigate a timevarying neutrino mass model, motivated by the mild tension between cosmic microwave background (CMB) measurements of the matter fluctuations and those obtained from lowredshift data. We modify the minimal case of the model proposed by [G. Dvali and L. Funcke, Phys. Rev. D 93, 113002 (2016)PRVDAQ2470001010.1103/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 latetime 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 constantmass 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 timevarying neutrino mass model considered here does not provide a clear explanation of the existing cosmological Ωmσ8 discrepancies.

Constraining the invisible neutrino decay with KM3NeTORCA
arXiv:1810.10916 Phys.Lett. B789 (2019) 472479
by: de Salas, P.F. (Valencia U., IFIC) et al.
Abstract: 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 KM3NeTORCA experiment to this scenario and find that it could improve the current bounds coming from oscillation experiments, where threeneutrino 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 sin2θ23 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
arXiv:1810.10579 Rev.Phys. (2018) 100027 Rev.Phys. 4 (2019) 100027
by: Rappoccio, Salvatore (SUNY, Buffalo)
Abstract: 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 protonproton 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
arXiv:1810.06795 Phys.Lett. B789 (2019) 603604
by: Fernandez, Nicolas (UC, Santa Cruz) et al.
Abstract: 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 nonstandard 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 NeutrinoNucleus Scattering
arXiv:1810.05606 Phys.Rev. D98 (2018) 113010
by: Cadeddu, M. (Cagliari U.) et al.
Abstract: Coherent elastic neutrinonucleus 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
arXiv:1810.00893 Phys.Rev. D98 (2018) 123023
by: Ahlers, Markus (Bohr Inst.) et al.
Abstract: The flavor composition of astrophysical neutrinos observed at neutrino telescopes is related to the initial composition at their sources via oscillationaveraged 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 TeVPeV astrophysical neutrinos based on unitarity constraints. These bounds are useful for studying the flavor composition of highenergy neutrinos, where energydependent nonstandard 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
arXiv:1810.01000 Phys.Rev. D99 (2019) 015016
by: Liao, Jiajun (Hawaii U.) et al.
Abstract: 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 eVmass sterile neutrino. We show that an apparently consistent picture can be drawn if chargedcurrent and neutralcurrent 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 OffAxis Liquid Argon Neutrino Detectors
arXiv:1809.06388 FERMILABPUB18433T NUHEPTH/1810 JHEP 1901 (2019) 001
by: de Gouvêa, André (Northwestern U.) et al.
Abstract: We present dark tridents, a new channel for exploring dark sectors in shortbaseline 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 leptonantilepton pair. Dark trident production occurs in models where longlived darksector particles are produced along with the neutrinos in a beamdump environment and interact with neutrino detectors downstream, producing an onshell 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 standardmodel 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 offaxis 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
arXiv:1809.06229 J.Phys. G46 (2019) 023001
by: Bifani, Simone (Birmingham U.) et al.
Abstract: Several measurements of tree and looplevel bhadron 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 threebody decays of LongLived Particles with MATHUSLA
arXiv:1809.01683 Phys.Lett. B789 (2019) 127131
by: Ibarra, Alejandro (Munich, Tech. U.) et al.
Abstract: Several extensions of the Standard Model predict the existence of LongLived Neutral Particles (LLNPs) with masses in the multiGeV 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 largevolume surface detector installed near ATLAS or CMS aimed to probe scenarios with LLNPs which offers good prospects for disentangling the physics underlying twobody 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 threebody LLNP decays, as well as the prospects for reconstructing the underlying model parameters.

Addressing the Majorana vs. Dirac Question with Neutrino Decays
arXiv:1808.10518 FERMILABPUB18418T NUHEPTH/1809 Phys.Lett. B789 (2019) 488495
by: Balantekin, A. Baha (Wisconsin U., Madison) et al.
Abstract: 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 ultrarelativistic. Noting that Majorana neutrinos can behave quite differently from Dirac ones when they are nonrelativistic, 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 selfconjugate 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 nextgeneration of highenergy colliders, intense meson facilities, or neutrino beam experiments.

ModelIndependent Prediction of $R(\eta_c)$
arXiv:1808.07360 JHEP 1812 (2018) 114
by: Berns, Anson (Montgomery Blair High School) et al.
Abstract: We present a modelindependent 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, heavyquark relations at zerorecoil, 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.

BaryonLepton Duplicity as the Progenitor of LongLived Dark Matter
arXiv:1808.05417 UCRHEPT593 (Aug 2018) UCRHEPT593 Phys.Lett. B788 (2019) 442445
by: Ma, Ernest (UC, Riverside)
Abstract: 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 baryonlepton duplicity allows a scalar σ which couples to NLNL to be longlived dark matter.

Cosmic infrared background excess from axionlike particles and implications for multimessenger observations of blazars
arXiv:1808.05613 MPP2018213 Phys.Rev. D99 (2019) 023002
by: Kalashev, Oleg E. (Moscow, INR) et al.
Abstract: The first measurement of the diffuse background spectrum at 0.81.7 $\mu \rm{m}$ 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 gammaray flux and alleviates the tension between the detected neutrino and gamma ray fluxes.

Neutrino scattering and B anomalies from hidden sector portals
arXiv:1808.02611 MITH1887 JHEP 1901 (2019) 091
by: Datta, Alakabha (Mississippi U.) et al.
Abstract: 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 neutrinonucleus 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 spinflavour oscillations in transversal matter currents with standard and nonstandard interactions
arXiv:1808.00302 Phys.Rev. D98 (2018) 113009
by: Pustoshny, Pavel (Moscow State U.) et al.
Abstract: After a brief history of two known types of neutrino mixing and oscillations, including neutrino spin and spinflavor oscillations in the transversal magnetic field, we perform a systematic study of a new phenomenon of neutrino spin and spinflavor 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 spinflavor oscillations engendered by the transversal matter currents in the case of nonstandard interactions of neutrinos with background matter are also considered.

Simplest ScotoSeesaw Mechanism
arXiv:1807.11447 IFIC18XXX Phys.Lett. B789 (2019) 132136
by: Rojas, Nicolás (Santa Maria U., Valparaiso) et al.
Abstract: By combining the simplest (3,1) version of the seesaw mechanism containing a single heavy "righthanded" 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
arXiv:1807.07988 Phys.Rev. D98 (2018) 115025
by: Kang, Sin Kyu (Seoul, Nat. U. Technol.) et al.
Abstract: 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 oneloop 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
arXiv:1807.07938 Prog.Part.Nucl.Phys. 104 (2019) 145
by: Boyarsky, A. (Leiden U.) et al.
Abstract: 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 keVscale sterile neutrinos, highlighting their experimental challenges and discovery potential.

Limits on Neutrino Lorentz Violation from Multimessenger Observations of TXS 0506+056
arXiv:1807.05155 KCLPHTH/201837 CERNTH/2018166 KCLPHTH201837 CERNTH2018166 Phys.Lett. B789 (2019) 352355
by: Ellis, John (King's Coll. London) et al.
Abstract: The observation by the IceCube Collaboration of a highenergy ($E \gtrsim 200$ 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 RightHanded Neutrino Portal Dark Matter With Yukawa Effect
arXiv:1807.05122 IITHPH0003/18 IIPDM201808 IITHPH000318 Phys.Lett. B788 (2019) 530534
by: Bandyopadhyay, Priyotosh (Indian Inst. Tech., Hyderabad) et al.
Abstract: Analyzing the neutrino Yukawa effect in the freezeout process of a generic dark matter candidate with righthanded neutrino portal, we identify the parameter regions satisfying the observed dark matter relic density as well as the current FermiLAT and H.E.S.S. limits and the future CTA reach on gammaray signals. In this scenario the dark matter couples to the Higgs boson at oneloop level and thus could be detected by spinindependent nucleonic scattering for a reasonable range of the relevant parameters.

Interpretation of the coincident observation of a high energy neutrino and a bright flare
arXiv:1807.04275 Nat.Astron. 3 (2019) 8892
by: Gao, Shan (DESY, Zeuthen) et al.
Abstract: 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 followup campaigns, and the Fermi gammaray 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 highenergy 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 selfconsistent description of the processes at work. Here we perform a detailed timedependent modeling of these relevant processes and study a set of selfconsistent models for the source. We find a slow but overproportional increase of the neutrino flux during the flare compared to the production enhancement of energetic cosmic rays. We also demonstrate that interactions of energetic cosmicray ions result in predominantly hard Xray emission, strongly constraining the expected number of neutrinos, and to a lesser degree in TeV gamma rays. Optical photons and GeVscale gamma rays are predominantly radiated by electrons. Our results indicate that especially future Xray and TeVscale gammaray observations of nearby objects can be used to identify more such events.

Beta and Neutrinoless Double Beta Decays with KeV Sterile Fermions
arXiv:1807.01331 LPTOrsay1863 LPTORSAY1863 JHEP 1901 (2019) 041
by: Abada, Asmaa (Orsay, LPT) et al.
Abstract: Motivated by the capability of the KATRIN experiment to explore the existence of KeV neutrinos in the $[118.5]$ 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 lowscale seesaw realizations involving KeV sterile neutrinos. Our study concerns the prospect of a TypeI seesaw with two righthanded neutrinos, and a combination of the inverse and the linear seesaws where the Standard Model is minimally extended by two quasidegenerate sterile fermions. We also discuss the possibility of exploring the latter case searching for doublekinks in KATRIN.

Lepton Masses and Mixing from Modular $S_4$ Symmetry
arXiv:1806.11040 SISSA 25/2018/FISI IPMU180121 SISSA252018FISI Nucl.Phys. B939 (2019) 292307
by: Penedo, J.T. (INFN, Trieste) et al.
Abstract: 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
arXiv:1806.10685 Phys.Lett. B789 (2019) 5970
by: Borah, Debasish (Indian Inst. Tech., Guwahati) et al.
Abstract: 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
arXiv:1806.05266 Nucl.Instrum.Meth. A921 (2019) 7180
by: Toki, Walter (Colorado State U.) et al.
Abstract: The pvalue 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 pvalues 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 $B^{+} \to K^{(*)\pm}\mu^+\mu^{\mp}$
arXiv:1806.03786 Chin.Phys. C43 (2019) 023101
by: Li, Honglei (Jinan U., Jinan) et al.
Abstract: 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, TypeI 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 samesign 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 HighScale Leptogenesis
arXiv:1806.00460 IPPP/18/40 FERMILABPUB18222T UCITR201805 IPPP1840 JHEP 1812 (2018) 111
by: Ipek, Seyda (UC, Irvine) et al.
Abstract: We consider the requirements that all coupling constants remain perturbative and the electroweak vacuum metastable up to the Planck scale in highscale thermal leptogenesis, in the context of a typeI 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 Lorentzviolating parameters at DUNE
arXiv:1805.11094 FTUV180531 IFIC1823 Phys.Lett. B788 (2019) 308315
by: Barenboim, Gabriela (Valencia U.) et al.
Abstract: 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 Lorentzviolating 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 LeftRight Extended Zee Model
arXiv:1805.09844 IPBBSR20186 Phys.Rev. D98 (2018) 115038
by: Khan, Sarif (HarishChandra Res. Inst.) et al.
Abstract: We study a simple leftright symmetric (LRS) extension of the Zee model for neutrino mass generation. An extra $SU(2)_{L/R}$ singlet charged scalar helps in generating a loopinduced Majorana mass for neutrinos in this model. The righthanded 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 crosssection 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
CERNTH/2018114 LAPTH018/18 CERNTH2018114 LAPTH01818 arXiv:1805.09857 JHEP 1812 (2018) 121
by: Re, Emanuele (CERN) et al.
Abstract: We present novel predictions for the production of $W^+W^$ pairs in hadron collisions that are nexttonexttoleading 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 offshell 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 softgluon effects and from the large impact ($10$% and more) of including nexttonexttoleading 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
arXiv:1804.07241 JHEP 1901 (2019) 066
by: Pandey, Madhurima (Saha Inst.)
Abstract: 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.

CPTSymmetric Universe
arXiv:1803.08928 Phys.Rev.Lett. 121 (2018) 251301
by: Boyle, Latham (Perimeter Inst. Theor. Phys.) et al.
Abstract: 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 postbang epochs comprise a universe/antiuniverse pair, emerging from nothing directly into a hot, radiationdominated 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 threegeneration model of particle physics (with righthanded neutrinos), a $\mathbb{Z}_2$ symmetry suffices to render one of the righthanded 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 longwavelength gravitational waves. We mention connections to the strong CP problem and the arrow of time.

New physics searches in nuclear and neutron $\beta$ decay
arXiv:1803.08732 CERNTH2018050 Prog.Part.Nucl.Phys. 104 (2019) 165223
by: GonzalezAlonso, Martin (CERN) et al.
Abstract: 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 modelindependent 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 highenergy 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 righthanded 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 highenergy probes is presented including ongoing searches at the Large Hadron Collider.

Neutrino tomography of the Earth
IFC/1752 arXiv:1803.05901 IFC1752 Nature Phys. 15 (2019) 3740
by: Donini, Andrea (Valencia U., IFIC) et al.
Abstract: Cosmicray 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 chargedcurrent neutrinonucleon cross section is large enough so that the neutrino meanfree 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 nonnegligible 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 oneyear throughgoing 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
arXiv:1803.00662 Phys.Rev. C98 (2018) 065806
by: Alford, Mark G. (Washington U., St. Louis) et al.
Abstract: We show that the commonly used criterion for beta equilibrium in neutrinotransparent 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 1020 MeV, depending on the temperature at which neutrinos become trapped.

Scaledependent galaxy bias, CMB lensinggalaxy crosscorrelation, and neutrino masses
arXiv:1802.08694 Phys.Rev. D98 (2018) 123526
by: Giusarma, Elena (LBL, Berkeley) et al.
Abstract: 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 scaledependent galaxy bias $b(k)$. In this Letter we present a new method to constrain $b(k)$ by using the crosscorrelation between the Cosmic Microwave Background (CMB) lensing signal and galaxy maps ($C_\ell^{\rm \kappa g}$) using a simple but theoretically wellmotivated parametrization for $b(k)$. We apply the method using $C_\ell^{\rm \kappa g}$ measured by crosscorrelating 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 nonzero scaledependence at moderate significance, which suggests that a proper modeling of $b(k)$ is necessary in order to reduce the impact of nonlinearities 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 largescale structure surveys will overlap more significantly with the CMB lensing kernel providing a large crosscorrelation signal.

Precision Physics at LEP
MPP2017263 arXiv:1712.03035
by: Bethke, Siegfried (Munich, Max Planck Inst.)
Abstract: 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 ElectronPositron 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
arXiv:1712.03148 Phys.Dark Univ. 100261 Phys.Dark Univ. 23 (2019) 100261
by: Feng, Lu (Shenyang, Northeast U. Tech.) et al.
Abstract: 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 largescale instability in the interacting dark energy scenario, we employ the parametrized postFriedmann (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 typeIa supernova data, the Hubble constant direct measurement, the galaxy weak lensing data, the redshift space distortion data, and the Planck lensing data. Using the alldata 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
arXiv:1711.07396 Chin.Phys. C43 (2019) 023102
by: Cai, Chengfeng (SYSU, Guangzhou) et al.
Abstract: We confront the perturbativity problem in the real scalar quintuplet minimal dark matter model. In the original model, the quintuplet quartic selfcoupling 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 typeI 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.

NeutrinoOxygen CC0$\pi$ scattering in the SuSAv2MEC model
arXiv:1711.00771 JLABTHY172586 J.Phys. G46 (2019) 015104
by: Megias, G.D. (Seville U.) et al.
Abstract: We present the predictions of the SuSAv2MEC model for the double differential chargedcurrent 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
arXiv:1707.01286 Nucl.Phys. B938 (2019) 56113
by: Sahoo, Biswonath (Siksha O Anusandhan U., Bhubaneswar) et al.
Abstract: In direct breaking of nonsupersymmetric SO(10) to the standard model, we investigate the possibility that dark matter (DM) decaying through its mixing with righthanded neutrino (RH$\nu$) produces high energy IceCube neutrinos having typeI 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 quarklepton 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 Planckscale assisted spontaneously broken matter parity needed to resolve the associated cosmological domain wall problem. This leads to the prediction of a new LHC accessible matterparity 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?
DFPD2017TH09 arXiv:1706.08749
by: Feruglio, Ferruccio (INFN, Padua)
Abstract: 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 higherdimensional 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 nonlinearly realised symmetries to the discrete case.

Neutrinoless double beta decay in minimal leftright symmetric model with universal seesaw
arXiv:1706.02456 Int.J.Mod.Phys. A33 (2018) 1850198
by: Borah, Debasish (Indian Inst. Tech., Guwahati) et al.
Abstract: 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 righthanded 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 righthanded 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 halflife cancel each other due to unitarity of the total 6 × 6 mass matrix. The effective contribution to halflife 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.
