
Lepton Flavor Violation in a $Z^\prime$ model for the $b \to s$ anomalies
arXiv:1810.02135 IFIC/1834 BONNTH201813
by: RochaMoran, Paulina Abstract: In recent years, several observables associated to semileptonic $b \to s$ processes have been found to depart from their predicted values in the Standard Model, including a few tantalizing hints of lepton flavor universality violation. In this work we consider an existing model with a massive $Z^\prime$ boson that addresses the anomalies in $b \to s$ transitions and extend it with a nontrivial embedding of neutrino masses. We analyze lepton flavor violating effects, induced by the nonuniversal interaction associated to the $b \to s$ anomalies and by the new physics associated to the neutrino mass generation, and determine the expected ranges for the most relevant observables.

General Neutrino Interactions at the DUNE Near Detector
arXiv:1810.02220
by: Bischer, Ingolf Abstract: We consider the effect of general neutrino interactions (scalar, vector, pseudoscalar, axial vector and tensor) in neutrinoelectron scattering at the DUNE near detector. Those interactions can be associated with heavy new physics and their effect is to cause distortions in the recoil spectrum of the electrons. We show that for some cases energy scales up to 9 TeV are accessible after a 5 year run and that current bounds on interaction parameters can be improved by up to an order of magnitude. The full set of general interactions includes the usually considered neutrinoelectron nonstandard matter interactions, and the near detector will give limits comparable but complementary to the ones from the analysis of neutrino oscillations in the far detector.

Lorentz violation from gammaray burst neutrinos
arXiv:1810.01652 APS Physics 1 (2018) 62
by: Huang, Yanqi (Peking U.) et al.
Abstract: The Lorentz violation~(LV) effect of ultrarelativistic particles can be tested by gammaray burst~(GRB) neutrinos and photons. The IceCube Collaboration has observed plenty of ultrahigh energy neutrinos, including four events of PeV scale neutrinos. Recent studies suggested a possible energy dependent speed variation of GRB neutrinos in a similar way to that of GRB photons. Here we find that all four events of PeV neutrinos with associated GRB candidates can satisfy a regularity found from TeV neutrinos about a linear form correlation between the observed time difference and the LV factor. Such regularity indicates a Lorentz violation scale $E_{\rm LV}=(6.5\pm 0.4)\times10^{17}~{\rm GeV}$, which is comparable with that determined by GRB photons. We also suggest that neutrinos and antineutrinos can be superluminal and subluminal respectively due to opposite signs of LV correction.

A New Era in the Quest for Dark Matter
arXiv:1810.01668
by: Bertone, Gianfranco Abstract: There is a growing sense of `crisis' in the dark matter community, due to the absence of evidence for the most popular candidates such as weakly interacting massive particles, axions, and sterile neutrinos, despite the enormous effort that has gone into searching for these particles. Here, we discuss what we have learned about the nature of dark matter from past experiments, and the implications for planned dark matter searches in the next decade. We argue that diversifying the experimental effort, incorporating astronomical surveys and gravitational wave observations, is our best hope to make progress on the dark matter problem.

$\Delta \left( 27\right)$ flavor singlettriplet Higgs model for fermion masses and mixings
arXiv:1810.01764
by: Cárcamo Hernández, A.E. (Santa Maria U., Valparaiso) et al.
Abstract: We propose a multiscalar singlet extension of the singlettriplet Higgs model consistent with the low energy fermion flavor data. Our model is based on the $\Delta \left( 27\right) $ family symmetry, which is supplemented with the $Z_{16}\times Z_{24}$ discrete group. The observed hierarchy of the SM charged fermion masses and quark mixing angles arises from the breaking of the $\Delta \left( 27\right) \times Z_{16}\times Z_{24}$ discrete group, whereas the light active neutrino masses are generated from a typeII seesaw mechanism mediated by the neutral component of the $SU(2)_{L}$ scalar triplet. The model symmetries lead to the extended GattoSartoriTonin relations between the quark masses and mixing angles.

Flavor Energy uncertainty relations for neutrino oscillations in quantum field theory
arXiv:1810.01648
by: Blasone, Massimo (Salerno U.) et al.
Abstract: In the context of quantum field theory, we derive flavor energy uncertainty relations for neutrino oscillations. By identifying the non conserved flavor charges with the clock observables, we arrive at the Mandelstam Tamm version of time energy uncertainty relations. In the ultrarelativistic limit these relations yield the well known condition for neutrino oscillations. Ensuing non relativistic corrections to the latter are explicitly evaluated. The analogy among flavor states and unstable particles and a novel interpretation of our uncertainty relations, based on the unitary inequivalence of Fock spaces for flavor and massive neutrinos, are also discussed.

Flavor of cosmic neutrinos preserved by ultralight dark matter
arXiv:1810.00892 IFIC/1836
by: Farzan, Yasaman (IPM, Tehran) et al.
Abstract: Within the standard propagation scenario, the flavor ratios of highenergy cosmic neutrinos at neutrino telescopes are expected to be around the democratic benchmark resulting from hadronic sources, $\left( 1 : 1 : 1 \right)_\oplus$. We show how the coupling of neutrinos to an ultralight dark matter complex scalar field would induce an effective neutrino mass that could lead to adiabatic neutrino propagation. This would result in the preservation at the detector of the production flavor composition of neutrinos at sources. This effect could lead to flavor ratios at detectors well outside the range predicted by the standard scenario of averaged oscillations. We also present an electroweakinvariant model that would lead to the required effective interaction between neutrinos and dark matter.

Exploring the ultralight to subMeV dark matter window with atomic clocks and comagnetometers
arXiv:1810.00889 CERNTH2018209 KCLPHTH/201850
by: Alonso, Rodrigo (CERN) et al.
Abstract: Particle dark matter could have a mass anywhere from that of ultralight candidates, $m_\chi\sim 10^{21}\,$eV, to scales well above the GeV. Conventional laboratory searches are sensitive to a range of masses close to the weak scale, while new techniques are required to explore candidates outside this realm. In particular lighter candidates are difficult to detect due to their small momentum. Here we study two experimental setups which {\it do not require transfer of momentum} to detect dark matter: atomic clocks and comagnetometers. These experiments probe dark matter that couples to the spin of matter via the very precise measurement of the energy difference between atomic states of different angular momenta. This coupling is possible (even natural) in most dark matter models, and we translate the current experimental sensitivity into implications for different dark matter models. It is found that the constraints from current atomic clocks and comagnetometers can be competitive in the mass range $m_\chi\sim 10^{21}10^3\,$eV, depending on the model. We also comment on the (negligible) effect of different astrophysical neutrino backgrounds.

Unitarity Bounds of Astrophysical Neutrinos
arXiv:1810.00893
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
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 a 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.

Higgs Criticality in a Viable Motivated Model
arXiv:1810.00792 CERNTH2018213
by: Salvio, Alberto (CERN)
Abstract: An extension of the Standard Model with three righthanded neutrinos and a simple invisible axion model can account for all experimentally confirmed signals of new physics (neutrino oscillations, dark matter and baryon asymmetry) in addition to solving the strong CP problem, stabilizing the electroweak vacuum and satisfying all current observational bounds. We show that this model can also implement critical Higgs inflation, which corresponds to the frontier between stability and metastability of the electroweak vacuum. This leads to a value of the nonminimal coupling between the Higgs and the Ricci scalar that is much lower than the one usually quoted in Higgs inflation away from criticality. Then, an advantage is that the scale of perturbative unitarity breaking on flat spacetime can be very close to the Planck mass, where anyhow new physics is required. The higher dimensional operators are under control in this inflationary setup. The dependence of the cutoff on the Higgs background is also taken into account as appropriate when the Higgs is identified with the inflaton. Furthermore, critical Higgs inflation enjoys a robust inflationary attractor that makes it an appealing setup for the early universe. In the proposed model, unlike in the Standard Model, critical Higgs inflation can be realized without any tension with the observed quantities, such as the top mass and the strong coupling.

On the capture rates of big bang neutrinos by nuclei within the Dirac and Majorana hypotheses
arXiv:1810.00505
by: Roulet, Esteban (Centro Atomico Bariloche) et al.
Abstract: The capture rates of nonrelativistic neutrinos on beta decaying nuclei depends on whether their mass is Dirac or Majorana. It is known that for relic neutrinos from the bigbang, and within minimal assumptions, the rate is a factor two larger in the Majorana case. We show that this difference also depends on the value of the lightest neutrino mass and on the type of mass hierarchy. If the lightest neutrino has a mass below the meV, so that it is still relativistic today, its capture rate for the case of Dirac masses becomes equal to that for Majorana masses. As a consequence, for the case of normal neutrino mass hierarchy, for which the total capture rate is dominated by the contribution from the lightest neutrino, if this one is below the meV the distinction between the Dirac and Majorana scenarios can only rely on the detection of the two heavier neutrinos, which is something very challenging.

On the scattering of a highenergy cosmic ray electrons off the dark matter
arXiv:1810.00372
by: Beylin, V. (Southern Federal U.) et al.
Abstract: Highenergy cosmic ray electrons interaction with Dark Matter particles are considered. In particular, a weakening of energy spectrum of cosmic electrons is predicted resulting from inelastic electron scattering on hyperpions in the hypercolor extension of the Standard Model. Corresponding cross section and angular distributions of secondary neutrino are calculated and studied. We also briefly discuss some effects of scattering processes of such type.

Detecting CP Violation in the Presence of NonStandard Neutrino Interactions
arXiv:1809.11128 CIPANP2018Hyde
by: Hyde, Jeffrey M. (Johns Hopkins U.)
Abstract: New physics beyond the Standard Model could appear at long baseline oscillation experiments as nonstandard interactions (NSI) between neutrinos and matter. If so, determination of the CPviolating phase $\delta_{13}$ is ambiguous due to interference with additional complex phases. I'll present my work using both numerical solutions and a perturbative approach to study oscillation probabilities in the presence of NSI. I'll show how the CP phase degeneracies are visualized on biprobability plots, and the extent to which the energy spectrum for a given baseline length can help resolve them. In particular, this shows how the broad range of energies at DUNE would help distinguish between maximal, standard CP violation and the absence of CP violation with large $\epsilon_{e\tau}$.

Constraining neutrino mass with tomographic weak lensing onepoint probability distribution function and power spectrum
arXiv:1809.10747
by: Liu, Jia (Princeton U. (main)) et al.
Abstract: We study the constraints on neutrino mass sum (M_nu) from the onepoint probability distribution function (PDF) and power spectrum of weak lensing measurements for an LSSTlike survey, using the MassiveNuS simulations. The PDF provides access to nonGaussian information beyond the power spectrum. It is particularly sensitive to nonlinear growth on small scales, where massive neutrinos also have the largest effect. We find that tomography helps improve the constraint on M_nu by 14% and 32% for the power spectrum and the PDF, respectively, compared to a single redshift bin. The PDF alone outperforms the power spectrum in constraining M_nu. When the two statistics are combined, the constraint is further tightened by 35%. We conclude that weak lensing PDF is complementary to the power spectrum and has the potential to become a powerful tool for constraining neutrino mass.

Effects of LESA in ThreeDimensional Supernova Simulations with MultiDimensional and RaybyRayplus Neutrino Transport
arXiv:1809.10150
by: Glas, Robert (Garching, Max Planck Inst.) et al.
Abstract: A set of eight selfconsistent, timedependent supernova (SN) simulations in three spatial dimensions (3D) for 9 solarmass and 20 solarmass progenitors is evaluated for the presence of dipolar asymmetries of the electron leptonnumber emission as discovered by Tamborra et al. and termed leptonnumber emission selfsustained asymmetry (LESA). The simulations were performed with the AenusAlcar neutrino/hydrodynamics code, which treats the energy and velocitydependent transport of neutrinos of all flavors by a twomoment scheme with algebraic M1 closure. For each of the progenitors, results with fully multidimensional (FMD) neutrino transport and with raybyrayplus (RbR+) approximation are considered for two different grid resolutions. While the 9 solarmass models develop explosions, the 20 solarmass progenitor does not explode with the employed version of simplified neutrino opacities. In all 3D models we observe the growth of substantial dipole amplitudes of the leptonnumber (electron neutrino minus antineutrino) flux with stable or slowly timeevolving direction and overall properties fully consistent with the LESA phenomenon. Models with RbR+ transport develop LESA dipoles somewhat faster and with temporarily higher amplitudes, but the FMD calculations exhibit cleaner hemispheric asymmetries with a far more dominant dipole. In contrast, the RbR+ results display much wider multipole spectra of the neutrinoemission anisotropies with significant power also in the quadrupole and higherorder modes. Our results disprove speculations that LESA is a numerical artifact of RbR+ transport. We also discuss LESA as consequence of a dipolar convection flow inside of the nascent neutron star and establish, tentatively, a connection to Chandrasekhar's linear theory of thermal instability in spherical shells.

ManyBody NeutrinoExchange Interactions and Neutrino Mass: Comment on Phys. Rev. Lett. 120, 223202 (2018)
arXiv:1809.09731
by: Fischbach, E. (Purdue U.)
Abstract: This Comment corrects an erroneous remark by Stadnik in a recent paper to the effect that manybody neutrinomediated forces are suppressed in all types of stars.

Induced resonance makes light sterile neutrino Dark Matter cool
arXiv:1809.09123 INRTH2018022
by: Bezrukov, F. (Manchester U.) et al.
Abstract: We describe two new generation mechanisms for Dark Matter composed of sterile neutrinos with $O(1)$ keV mass. The model contains a light scalar field which coherently oscillates in the early Universe and modulates the Majorana mass of the sterile neutrino. In a region of model parameter space, the oscillations between active and sterile neutrinos are resonantly enhanced. This mechanism allows us to produce sterile neutrino DM with small mixing angle with active neutrinos, thus evading the Xray constraints. At the same time the spectrum of produced DM is much cooler, than in the case of ordinary oscillations in plasma, opening a window of lower mass DM, which is otherwise forbidden by structure formation considerations. In other regions of the model parameter space, where the resonance does not appear, another mechanism can operate: large field suppresses the activesterile oscillations, but instead sterile neutrinos are produced by the oscillating scalar field when the effective fermion mass crosses zero. In this case DM component is cold, and even 1 keV neutrino is consistent with the cosmic structure formation.

Constraining highenergy neutrinos from chokedjet supernovae with IceCube highenergy starting events
arXiv:1809.09610
by: Esmaili, Arman Abstract: Different types of corecollapse supernovae (SNe) have been considered as candidate sources of highenergy cosmic neutrinos. Strippedenvelope SNe, including energetic events like hypernovae and superluminous SNe, are of particular interest. They may harbor relativistic jets, which are capable of explaining the diversity among gammaray bursts (GRBs), lowluminosity GRBs, ultralong GRBs, and broadline Type Ib/c SNe. Using the sixyear IceCube data on highenergy starting events (HESEs), we perform an unbinned maximum likelihood analysis to search for spatial and temporal coincidences with 222 samples of SNe Ib/c. We find that the present data are consistent with the background only hypothesis, by which we place new upper constraints on the isotropicequivalent energy of cosmic rays, ${\mathcal E}_{\rm cr}\lesssim{10}^{52}~{\rm erg}$, in the limit that all SNe are accompanied by onaxis jets. Our results demonstrate that not only upgoing muon neutrinos but also HESE data enable us to constrain the potential contribution of these SNe to the diffuse neutrino flux observed in IceCube. We also discuss implications for the nextgeneration neutrino detectors such as IceCubeGen2.

Majorons as cold light dark matter
arXiv:1809.09413
by: Heeck, Julian (Brussels U.)
Abstract: Majorons are the Goldstone bosons of spontaneously broken lepton number and hence intimately connected to Majorana neutrino masses. Since all majoron couplings are heavily suppressed by the seesaw scale they are interesting candidates for longlived dark matter. The signature decay into two monoenergetic neutrinos is potentially detectable with neutrino detectors for majoron masses above MeV and complementary to the loopinduced decays into visible particles. The mass range between keV and MeV can only be probed indirectly with the majoron decay into two photons; keVscale majorons can be warm or cold dark matter depending on the underlying freezein mechanism.

Impact of Matter Density Profile Shape on NonStandard Interactions at DUNE
arXiv:1809.09313
by: Chatterjee, Animesh (Texas U., Arlington) et al.
Abstract: We discuss the impact of matter density profile shape on the determination of nonstandard neutrino matter interactions (NSI) in the context of the long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). The primary scientific goals of DUNE are to determine the neutrino mass hierarchy, the leptonic CP violation phase, and the existence of new physics beyond the standard model of particles. Here we study the role of different earth matter density profiles on the question of observing standard oscillation as wells as NSI at DUNE. We consider two different earth matter density profiles which are relevant for the DUNE baseline. We first discuss the impact of matter on both appearance and disappearance oscillation channels, then we demonstrate the effect of different matter density profiles on the determination of NSI. We consider four different scenarios of NSI and elucidate the effect at the oscillation probability and measurement of number of events at DUNE. In one case of study we show that a nonstandard complex phase $\phi_{e\tau}$ could significantly increase the sensitivity to different matter distributions along the baseline.

Normalmode Analysis for Collective Neutrino Oscillations
arXiv:1809.09137 MPP2018224 TIFRTH1825
by: Airen, Sagar (Indian Inst. Tech., Mumbai) et al.
Abstract: In an interacting neutrino gas, collective modes of flavor coherence emerge that can be propagating or unstable. We derive the general dispersion relation in the linear regime that depends on the neutrino energy and angle distribution. The essential scales are the vacuum oscillation frequency $\omega=\Delta m^2/(2E)$, the neutrinoneutrino interaction energy $\mu=\sqrt{2}G_{\rm F} n_\nu$, and the matter potential $\lambda=\sqrt{2}G_{\rm F} n_e$. Collective modes require nonvanishing $\mu$ and may be dynamical even for $\omega=0$ ('fast modes'), or they may require $\omega\not=0$ ('slow modes'). The growth rate of unstable fast modes can be fast itself (independent of $\omega$) or can be slow (suppressed by $\sqrt{\omega/\mu}$). We clarify the role of flavor mixing, which is ignored for the identification of collective modes, but necessary to trigger collective flavor motion. A large matter effect is needed to provide an approximate fixed point of flavor evolution, while spatial or temporal variations of matter and/or neutrinos are required as a trigger, i.e., to translate the disturbance provided by the mass term to seed stable or unstable flavor waves. We work out explicit examples to illustrate these points.

Low Scale LeftRight Symmetry and Naturally Small Neutrino Mass
arXiv:1809.09115
by: Brdar, Vedran (Heidelberg, Max Planck Inst.) et al.
Abstract: We consider the low scale ($10$  $100$ TeV) leftright symmetric model with "naturally" small neutrino masses generated through the inverse seesaw mechanism. The Dirac neutrino mass terms are taken to be similar to the masses of charged leptons and quarks in order to satisfy the quarklepton similarity condition. The inverse seesaw implies the existence of fermion singlets $S$ with Majorana mass terms as well as the "left" and "right" Higgs doublets. These doublets provide the portal for $S$ and break the leftright symmetry. The inverse seesaw allows to realize a scenario in which the large lepton mixing originates from the Majorana mass matrix of $S$ fields which has certain symmetry. The model contains heavy pseudoDirac fermions, formed by $S$ and the righthanded neutrinos, which have masses in the $1$ GeV  $100$ TeV range and can be searched for at current and future colliders such as LHC and FCCee as well as in SHiP and DUNE experiments. Their contribution to neutrinoless double beta decay is unobservable. The radiative corrections to the mass of the Higgs boson and the possibility for generating the baryon asymmetry of the Universe are discussed. Modification of the model with two singlets ($S_L$ and $S_R$) per generation can provide a viable keVscale dark matter candidate.

Late time supernova neutrino signal and protoneutron star radius
arXiv:1809.09074
by: Gallo Rosso, A. (GSSI, Aquila) et al.
Abstract: We discuss the possibility of reconstructing the newly formed protoneutron star radius from the late time neutrino signal. A blackbody emission is assumed for the neutron star cooling phase. We parametrize the neutrino timeintegrated fluxes based on simulations of Roberts and Reddy. A likelihood analysis of the inversebeta decay and elastic scattering events in HyperKamiokande is performed in both three flavor and an effective one flavor scenario. We show that the precision achievable in the radius reconstruction strongly depends on a correlation with the pinching parameter and therefore the corresponding prior. Although this correlation hinders the precise measurement of the newly formed neutron star radius, it could help measure the pinching parameters with good accuracy in view of the current constraints on neutron star radius, or if the neutron star radius is precisely measured.

A Novel Approach to NeutrinoHydrogen Measurements
arXiv:1809.08752
by: Duyang, H. (South Carolina U.) et al.
Abstract: The lack of high statistics samples of (anti)neutrinohydrogen interactions has been a longstanding impediment for neutrino physics. We propose a practical way to achieve accurate (anti)neutrinohydrogen measurements, solving some of the principal limitations of neutrino experiments. Interactions on hydrogen are extracted by subtracting measurements on a dedicated graphite (pure C) target from those on a dedicated polypropylene (CH$_2$) target within a highly segmented detector. A statistics of ${\cal O}(10^6)$ can be realistically achieved for the various $\nu(\bar \nu)$H event topologies, with efficiencies exceeding 90\% and purities around 8092\%. The availability of such samples allows a determination of neutrino and antineutrino fluxes with unprecedented precision, as well as, by contrasting these samples to corresponding measurements on heavy materials, a measurement of initial and final state nuclear effects. The systematic uncertainties associated with both the fluxes and the nuclear smearing are crucial for modern longbaseline neutrino oscillation experiments. (Anti)neutrinohydrogen interactions also provide an ideal tool for a wide range of precision tests of fundamental interactions.

Leptogenesis from Low Energy $CP$ Violation
arXiv:1809.08251 IPPP/18/79 SISSA 38/2018/FISI IPMU180151 FERMILABPUB18382T
by: Moffat, K. (Durham U., IPPP) et al.
Abstract: We revisit the possibility of producing the observed baryon asymmetry of the Universe via thermal leptogenesis, where $CP$ violation comes exclusively from the lowenergy phases of the neutrino mixing matrix. We demonstrate the viability of thermal leptogenesis across seven orders of magnitude $\left(10^{6}

Chargedcurrent scattering off $^{16}$O nucleus as a detection channel for supernova neutrinos
arXiv:1809.08398
by: Nakazato, Ken'ichiro Abstract: Event spectra of the neutrino$^{16}$O chargedcurrent reactions in SuperKamiokande are evaluated for a future supernova neutrino burst. Since these channels are expected to be useful for diagnosing a neutrino spectrum with high average energy, the evaluations are performed not only for an ordinary supernova neutrino model but also for a model of neutrino emission from a blackholeforming collpase. Using shell model results, whose excitation energies are consistent with the experimental data, the cross sections of the $^{16}$O($\nu_e, e^$)X and $^{16}$O($\bar\nu_e, e^+$)X reactions for each nuclear state with a different excitation energy are employed in this study. It is found that, owing to the components of the reaction with higher excitation energy, the event spectrum becomes 47 MeV softer than that in the case without considering the excitation energies. In addition, a simplified approach to evaluate the event spectra is proposed for convenience and its validity is examined.

Highlyboosted dark matter and cutoff for cosmicray neutrino through neutrino portal
arXiv:1809.08610
by: Yin, Wen (Beijing, Inst. High Energy Phys.)
Abstract: We study the cutoff for the cosmicray neutrino, set by the scattering with cosmic background neutrinos into dark sector particles through a neutrino portal interaction. We find that a large interaction rate is still viable, when the dark sector particles are mainly coupled to the ${\tau}$neutrino, so that the neutrino mean free path can be reduced to be O(10) Mpc over a wide energy range. If stable enough, the dark sector particle, into whom most of the cosmicray neutrino energy is transferred, can travel across the Universe and reach to the earth. The energy of them can be as large as O(EeV) if originates from a cosmogenic neutrino.

ModelIndependent Bounds on $R(J/\psi)$ via Dispersive Relations
arXiv:1809.08227 CIPANP2018Lamm
by: Lamm, Henry (Maryland U.)
Abstract: Modelindependent bounds on $R(J/\psi) \! \equiv \!\mathcal{BR} (B_c^+ \rightarrow J/\psi \, \tau^+\nu_\tau)/$ $\mathcal{BR} (B_c^+ \rightarrow J/\psi \, \mu^+\nu_\mu)$ are obtained through a combination of dispersive relations, heavyquark relations at zerorecoil, and the limited existing form factor determinations from lattice QCD. The resulting 95% confidencelevel bound, $0.20\leq R(J/\psi)\leq0.39$, agrees with the recent LHCb result at $1.3 \, \sigma$, and removes the dominant modeldependent uncertainty from theory predictions. Using the same techniques, a prediction of $R(\eta_c)=0.29(5)$ is obtained.

The Lyman$\alpha$ forest as a diagnostic of the nature of the dark matter
arXiv:1809.06585
by: Garzilli, Antonella (Bohr Inst.) et al.
Abstract: The observed Lyman$\alpha$ flux power spectrum (FPS) is suppressed on scales below $\sim~ 30~{\rm km~s}^{1}$. This cutoff could be due to the high temperature, $T_0$, and pressure, $p_0$, of the absorbing gas or, alternatively, it could reflect the free streaming of dark matter particles in the early universe. We perform a set of very high resolution cosmological hydrodynamic simulations in which we vary $T_0$, $p_0$ and the amplitude of the dark matter free streaming, and compare the FPS of mock spectra to the data. We show that the location of the dark matter freestreaming cutoff scales differently with redshift than the cutoff produced by thermal effects and is more pronounced at higher redshift. We, therefore, focus on a comparison to the observed FPS at $z>5$. We demonstrate that the FPS cutoff can be fit assuming cold dark matter, but it can be equally well fit assuming that the dark matter consists of $\sim 7$ keV sterile neutrinos in which case the cutoff is due primarily to the dark matter free streaming.

Symmetries and Algebraic Methods in Neutrino Physics
arXiv:1809.02539 J.Phys. G45 (2018) 113001
by: Balantekin, A.B. Abstract: Symmetry properties associated with neutrino propagation with or without a background of other particles, including neutrinos, is reviewed. The utility of symmetries is illustrated with examples chosen from the seesaw mechanism and both matterenhanced and collective neutrino oscillations. The role of symmetries in neutrino astrophysics is highlighted.

Matter Effect of Light Sterile Neutrino: An Exact Analytical Approach
arXiv:1808.03985 JHEP 1810 (2018) 021
by: Li, Wei (Jinan U.) et al.
Abstract: The light sterile neutrino, if it exists, will give additional contribution to matter effect when active neutrinos propagate through terrestrial matter. In the simplest 3+1 scheme, three more rotation angles and two more CPviolating phases in lepton mixing matrix make the interaction complicated formally. In this work, the exact analytical expressions for active neutrino oscillation probabilities in terrestrial matter, including sterile neutrino contribution, are derived. It is pointed out that this set of formulas contain information both in matter and in vacuum, and can be easily tuned by choosing related parameters. Based on the generic exact formulas, we present oscillation probabilities of typic medium and long baseline experiments. Taking NOνA experiment as an example, we show that in particular parameter space sterile neutrino gives important contribution to terrestrial matter effect, and Dirac phases play a vital role.

Impact of vector new physics couplings on $B_s \to (K,\,K^{\ast})\tau\nu$ and $B \to \pi\tau\nu$ decays
arXiv:1808.03790 Phys.Rev. D98 (2018) 055024
by: Rajeev, N. (NIT, Silchar) et al.
Abstract: Experimental measurements of $R_{D}$, $R_{D^*}$ and $R_{J/\Psi}$ in $B \to (D,\,D^{\ast})l\nu$ and $B_c \to J/\Psi l \nu$ decays mediated via $b \to c\,l\,\nu$ charged current interactions deviate from standard model prediction by $2.3\sigma$, $3.4\sigma$ and $2\sigma$, respectively. In addition, a deviation of $1.5\sigma$ from the standard model prediction has been witnessed in $\mathcal B(B \to \tau \nu)$ mediated via $b \to u\,l\,\nu$ charged current interactions as well. Motivated by the anomalies present in $B$ and $B_c$ meson decays, we analyze the corresponding $B_s \to (K,\,K^{\ast})\,\tau\,\nu$ and $B \to \pi\tau\nu$ semileptonic decays within the standard model and beyond. We use an effective field theory formalism in which $b \to c$ and $b \to u$ semileptonic decays are assumed to exhibit similar new physics patterns. We give the predictions of various observables such as the branching fractions, ratio of branching ratios, lepton side forward backward asymmetry, lepton polarization fraction and convexity parameter for $B_s \to (K,\,K^{\ast})\tau \nu$ and $B \to \pi\tau\nu$ decay channels within the standard model and within various NP scenarios.

Thermal production of light Dirac righthanded sneutrino dark matter
arXiv:1808.00764 EPHOU18010 Phys.Dark Univ. 22 (2018) 96100
by: Choi, KiYoung (Sungkyunkwan U.) et al.
Abstract: We consider the production of righthanded (RH) sneutrino dark matter in a model of Dirac neutrino where neutrino Yukawa coupling constants are very small. Dark matter RH sneutrinos are produced by scatterings and decays of thermal particles in the early Universe without reaching thermal equilibrium due to the small Yukawa couplings. We show that not only decays of thermal particles but also the thermal scatterings can be a dominant source as well as nonthermal production in a scenario with light sneutrinos and charged sleptons while other supersymmetric particles are heavy. We also discuss the cosmological implications of this scenario.

Charge Quantization and Neutrino Mass from Planckscale SUSY
arXiv:1808.00440 Phys.Lett. B785 (2018) 585590
by: Yin, Wen (Beijing, Inst. High Energy Phys.)
Abstract: We show a possibility for the charge quantization of the standard model (SM) particles. If a global symmetry makes the three copies of a generation and supersymmetry (SUSY) relates the Higgs boson to a lepton, all the charges of the SM particles can be quantized through gaugeanomaly cancellation. In the minimal model realizing the possibility, the gravitino mass around the Planckscale is needed to generate the SM couplings through (quantum) supergravity. Much below the Planckscale, the SM is obtained as the effective theory. Interestingly, if the gaugino masses are generated through anomaly mediation, one of the neutrino masses is predicted to be around the neutrino oscillation scales. In an extension of the model, millicharged particles can exist without introducing massless hidden photons.

Angular distributions in electroweak pion production off nucleons: odd parity hadron terms, strong relative phases and model dependence
arXiv:1807.11281 Phys.Rev. D98 (2018) 073001
by: Sobczyk, J. E. (Valencia U., IFIC) et al.
Abstract: The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the chargedcurrent and neutralcurrent neutrino and antineutrino pion production off nucleons, paying special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and timereversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three stateoftheart, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parityviolating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pionnucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations.

Neutrino masses and gauged $U(1)_\ell$ lepton number
arXiv:1807.09439 JHEP 1810 (2018) 015
by: Chang, WeFu (Taiwan, Natl. Tsing Hua U.) et al.
Abstract: We investigate the treelevel neutrino mass generation in the gauged $U(1)_\ell$ lepton model recently proposed by us [arXiv:1805.10382]. With the addition of one Standard Model(SM) singlet, $\phi_1(Y=0, \ell=1)$, and one SM triplet scalar, $T(Y=1,\ell=0)$, realistic lepton masses can be accommodated. The resulting magnitude of neutrino mass is given by $\sim v_t^3/v_L^2$, where $v_t$ and $v_L$ are the vacuum expectation values of $T$ and $\phi_1$, respectively, and it is automatically of the inverse seesaw type. Since $v_L$ is the lepton number violation scale we take it to be high, i.e. ${\cal O} \gtrsim (\mbox{TeV})$. Moreover, the induced lepton flavor violating processes and the phenomenology of the peculiar triplet are studied. An interesting bound, $0.1\lesssim v_t\lesssim24.1$ GeV, is obtained when taking into account the neutrino mass generation, $Br(\mu\rightarrow e \gamma)$, and the limits from oblique parameters, $\Delta S$ and $\Delta T$. Collider phenomenology of the SM triplets is also discussed.

$ {R}_{D^{\left(*\right)}},{R}_{K^{\left(*\right)}} $ and neutrino mass in the 2HDMIII with righthanded neutrinos
arXiv:1807.08530 JHEP 1809 (2018) 149
by: Li, ShaoPing (CCNU, Wuhan, Inst. Part. Phys.) et al.
Abstract: Given that the twoHiggsdoublet model of type III (2HDMIII) has the potential to address the $ {R}_{D^{\left(*\right)}} $ anomalies while the resolution to the $ {R}_{K^{\left(*\right)}} $ deficits requires new degrees of freedom within this framework, we consider in this paper a unified scenario where the lowscale typeI seesaw mechanism is embedded into the 2HDMIII, so as to accommodate the $ {R}_{D^{\left(*\right)}} $ and $ {R}_{K^{\left(*\right)}} $ anomalies as well as the neutrino mass. We first revisit the $ {R}_{D^{\left(*\right)}} $ anomalies and find that the current worldaveraged results can be addressed at 2σ level without violating the bound from the branching ratio $ \mathrm{\mathcal{B}}\left({B}_c^{}\to {\tau}^{}\overline{\nu}\right) $ ≤ 30%. The scenario predicts two subeV neutrino masses based on a decoupled heavy Majorana neutrino and two nearly degenerate Majorana neutrinos with mass around the electroweak scale. For the $ {R}_{K^{\left(*\right)}} $ anomalies, the same scenario can generate the required Wilson coefficients in the direction C$_{9 μ}^{NP}$ = − C$_{10 μ}^{NP}$ < 0, with $ \mathcal{O}(1) $ Yukawa couplings for the muon and the top quark.

Blazar Flares as an Origin of HighEnergy Cosmic Neutrinos?
arXiv:1807.04748 Astrophys.J. 865 (2018) 124
by: Murase, Kohta (Penn State U., University Park (main)) et al.
Abstract: We consider implications of highenergy neutrino emission from blazar flares, including the recent event IceCube170922A and the 2014–2015 neutrino flare that could originate from TXS 0506+056. First, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. Blazars are likely to be subdominant in the diffuse neutrino intensity at subPeV energies, and we show that blazar flares like those of TXS 0506+056 could make ≲1%–10% of the total neutrino intensity. We also argue that the neutrino output of blazars can be dominated by the flares in the standard leptonic scenario for their γray emission, and energetic flares may still be detected with a rate of . Second, we consider multimessenger constraints on the source modeling. We show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in Xrays and γrays. This implies that not only γray telescopes like Fermi but also Xray sky monitors such as Swift and MAXI are critical to test the canonical picture based on the singlezone modeling. We also suggest a twozone model that can naturally satisfy the Xray constraints while explaining the flaring neutrinos via either photomeson or hadronuclear processes.

The Bearable Compositeness of Leptons
arXiv:1807.04279 JHEP 1810 (2018) 017
by: Frigerio, Michele (U. Montpellier, L2C) et al.
Abstract: Partial compositeness as a theory of flavor in the lepton sector is assessed. We begin presenting the first systematic analysis of neutrino mass generation in this context, and identifying the distinctive mass textures. We then update the bounds from charged lepton flavor and CP violating observables. We put forward a $U(1)^3\times CP$ symmetry of the composite sector, in order to allow the new physics to be not far above the TeV scale. This hypothesis effectively suppresses the new contributions to the electron EDM and $\mu\to e\gamma$, by far the most constraining observables, and results in a novel pattern of flavor violation and neutrino masses. The CP violation in the elementarycomposite mixing is shown to induce a CKM phase of the correct size, as well as orderone phases in the PMNS matrix. We compare with the alternative possibility of introducing multiple scales of compositeness for leptons, that also allow to evade flavor and CP constraints. Finally, we examine violations of lepton flavor universality in $B$meson semileptonic decays. The neutralcurrent anomalies can be accommodated, predicting strong correlations among different lepton flavors, with a few channels close to the experimental sensitivity.

Flavored nonminimal left–right symmetric model fermion masses and mixings
arXiv:1807.02727 Eur.Phys.J. C78 (2018) 812
by: Garcés, E.A. (CINVESTAV, IPN) et al.
Abstract: A complete study on the fermion masses and flavor mixing is presented in a nonminimal leftright symmetric model (NMLRMS) where the ${\bf S}_{3}\otimes {\bf Z}_{2}\otimes {\bf Z}^{e}_{2}$ flavor symmetry drives the Yukawa couplings. In the quark sector, the mass matrices possess a kind of the generalized Fritzsch textures that allow us to fit the CKM mixing matrix in good agreement to the last experimental data. In the lepton sector, on the other hand, a soft breaking of the $\mu\leftrightarrow \tau$ symmetry provides a non zero and non maximal reactor and atmospheric angles, respectively. The inverted and degenerate hierarchy are favored in the model where a set of free parameters is found to be consistent with the current neutrino data.

Modelindependent bounds on $R(J/\psi)$
arXiv:1807.02730 JHEP 1809 (2018) 168
by: Cohen, Thomas D. (Maryland U.) et al.
Abstract: We present a modelindependent bound on $ R\left(J/\psi \right)\equiv \mathrm{\mathcal{B}}\mathrm{\mathcal{R}}\left({B}_C^{+}\to J/\psi {\tau}^{+}{\nu}_{\tau}\right)/\mathrm{\mathcal{B}}\mathrm{\mathcal{R}}\left({B}_C^{+}\to J/\psi {\mu}^{+}{\nu}_{\mu}\right) $ . This bound is constructed by constraining the form factors through a combination of dispersive relations, heavyquark relations at zerorecoil, and the limited existing determinations from lattice QCD. The resulting 95% confidencelevel bound, 0.20 ≤ R(J/ψ) ≤ 0.39, agrees with the recent LHCb result at 1.3σ, and rules out some previously suggested model form factors.

Revisiting $B \to \pi\pi \ell \nu$ at large dipion masses
EOS201801 SIHEP201823 QFET201814 TUMHEP1149/18 TUMHEP114918 arXiv:1807.01924 JHEP 1810 (2018) 030
by: Feldmann, Thorsten (Siegen U.) et al.
Abstract: We revisit QCD factorization of $B\to \pi\pi$ form factors at large dipion masses, by deriving new constraints based on the analyticity properties of these objects. We then propose a parametrization of the form factors, inspired by the leadingtwist QCD factorization formula, that incorporates all known analytic properties. This parameterization is used to interpolate between the QCDF results and the constraints from the $B^*$ pole. Based on this interpolation, we predict the $B\to \pi\pi\ell\nu$ decay rate in a larger phase space region than previous studies could. We obtain a partiallyintegrated branching ratio up to $\mathcal{B} \simeq \mathcal{O}({10^{6}})$, which implies that a measurement of the nonresonant semileptonic decay is potentially within reach of the Belle II experiment.

Oneloop effective LFV $\varvec{Zl_kl_m}$ vertex from heavy neutrinos within the mass insertion approximation
IFTUAM/CSIC1859 FTUAM1815 LPTOrsay1877 arXiv:1807.01698 IFTUAMCSIC1859 LPTORSAY1877 Eur.Phys.J. C78 (2018) 815
by: Herrero, M.J. (Madrid, Autonoma U.) et al.
Abstract: In this paper we study the effective lepton flavor violating vertex of an electroweak $Z$ gauge boson and two charged leptons with different flavor, $l_k$ and $l_m$, that is generated to oneloop in low scale seesaw models with right handed neutrinos whose masses are heavier than the electroweak scale. We first compute the form factor describing this vertex by using the mass insertion approximation, where the flavor nondiagonal entries of the neutrino Yukawa coupling matrix are the unique origin, to oneloop level, of lepton flavor changing processes with charged leptons in the external legs. Then, by considering the proper large right handed neutrino mass expansion of the form factor, we derive a formula for the $Z l_k l_m$ effective vertex which is very simple and useful for fast phenomenological estimates. In the last part of this work we focus on the phenomenological applications of this vertex for simple and accurate estimates of the $Z \to l_k {\bar l}_m$ decay rates. Concretely, this vertex will allow us to conclude easily on the maximum allowed decay rates by present data in the inverse seesaw model. The found rates are promising, at the reach of future lepton colliders.

Modelindependent diagnostic of selfinduced spectral equalization versus ordinary matter effects in supernova neutrinos
arXiv:1807.00840 TIFR/TH/1815 MPP2018147 TIFRTH1815 Phys.Rev. D98 (2018) 063013
by: Capozzi, Francesco (Munich, Max Planck Inst.) et al.
Abstract: Selfinduced flavor conversions near the supernova (SN) core can make the fluxes for different neutrino species become almost equal, potentially altering the dynamics of the SN explosion and washing out all further neutrino oscillation effects. We present a new modelindependent analysis strategy for the next galactic SN signal that will distinguish this flavor equalization scenario from a matter effects only scenario during the SN accretion phase. Our method does not rely on fitting or modelling the energydependent fluences of the different species to a known function, but rather uses a modelindependent comparison of chargedcurrent and neutralcurrent events at large nextgeneration underground detectors. Specifically, we advocate that the events due to elastic scattering on protons in a scintillator detector, which is insensitive to oscillation effects and can be used as a modelindependent normalization, should be compared with the events due to inverse beta decay of $\bar\nu_e$ in a water Cherenkov detector and/or the events due to chargedcurrent interactions of $\nu_e$ in an Argon detector. The ratio of events in these different detection channels allow one to distinguish a complete flavor equalization from a pure matter effect, for either of the neutrino mass orderings, as long as the spectral differences among the different species are not too small.

Probing the seesaw scale with gravitational waves
arXiv:1807.00336 EPHOU18007 Phys.Rev. D98 (2018) 063532
by: Okada, Nobuchika (Alabama U.) et al.
Abstract: The $U(1)_{BL}$ gauge symmetry is a promising extension of the standard model of particle physics, which is supposed to be broken at some high energy scale. Associated with the $U(1)_{BL}$ gauge symmetry breaking, righthanded neutrinos acquire their Majorana masses and then tiny light neutrino masses are generated through the seesaw mechanism. In this paper, we demonstrate that the firstorder phase transition of the $U(1)_{BL}$ gauge symmetry breaking can generate a large amplitude of stochastic gravitational wave (GW) radiation for some parameter space of the model, which is detectable in future experiments. Therefore, the detection of GWs is an interesting strategy to probe the seesaw scale which can be much higher than the energy scale of collider experiments.

Mutau symmetry and the Littlest Seesaw
arXiv:1807.00023 Phys.Lett. B785 (2018) 391398
by: King, Stephen F. (Southampton U.) et al.
Abstract: Motivated by the latest neutrino oscillation data which is consistent with maximal atmospheric mixing and maximal leptonic CP violation, we review various results in μτ symmetry, then include several new observations and clarifications, including identifying a new general form of neutrino mass matrix with μτ symmetry. We then apply the new results to the neutrino mass matrix associated with the Littlest Seesaw model, and show that it approximately satisfies the new general form with μτ symmetry, and that this is responsible for its approximate predictions of maximal atmospheric mixing and maximal CP violation in the lepton sector.

Coherent scattering and macroscopic coherence: Implications for neutrino, dark matter and axion detection
arXiv:1806.10962 JHEP 1810 (2018) 045
by: Akhmedov, Evgeny (Heidelberg, Max Planck Inst.) et al.
Abstract: We study the question of whether coherent neutrino scattering can occur on macroscopic scales, leading to a significant increase of the detection cross section. We concentrate on radiative neutrino scattering on atomic electrons (or on free electrons in a conductor). Such processes can be coherent provided that the net electron recoil momentum, i.e. the momentum transfer from the neutrino minus the momentum of the emitted photon, is sufficiently small. The radiative processes is an attractive possibility as the energy of the emitted photons can be as large as the momentum transfer to the electron system and therefore the problem of detecting extremely low energy recoils can be avoided. The requirement of macroscopic coherence severely constrains the phase space available for the scattered particle and the emitted photon. We show that in the case of the scattering mediated by the usual weak neutral current and charged current interactions this leads to a strong suppression of the elementary cross sections and therefore the requirement of macroscopic coherence results in a reduction rather than an increase of the total detection cross section. However, for the $\nu e$ scattering mediated by neutrino magnetic or electric dipole moments coherence effects can actually increase the detection rates. Effects of macroscopic coherence can also allow detection of neutrinos in 100 eV  a few keV energy range, which is currently not accessible to the experiment. A similar coherent enhancement mechanism can work for relativistic particles in the dark sector, but not for the conventionally considered nonrelativistic dark matter.

The Fundamental Need for a SM Higgs and the Weak Gravity Conjecture
arXiv:1806.09647 IFTUAMCSIC1864 Phys.Lett. B786 (2018) 272277
by: Gonzalo, Eduardo (Madrid, IFT) et al.
Abstract: Compactifying the SM down to 3D or 2D one may obtain AdS vacua depending on the neutrino mass spectrum. It has been recently shown that, by insisting in the absence of these vacua, as suggested by {\it Weak Gravity Conjecture} (WGC) arguments, intriguing constraints on the value of the lightest neutrino mass and the 4D cosmological constant are obtained. For fixed Yukawa coupling one also obtains an upper bound on the EW scale $\left\langle H\right\rangle\lesssim {\Lambda_4^{1/4}} /{Y_{\nu_{i}}}$,where $\Lambda_4$ is the 4D cosmological constant and $Y_{\nu_{i}}$ the Yukawa coupling of the lightest (Dirac) neutrino. This bound may lead to a reassessment of the gauge hierarchy problem. In this letter, following the same line of arguments, we point out that the SM without a Higgs field would be inconsistent with a quantum gravity embedding, giving a fundamental basis for the very existence of the SM Higgs. Furthermore one can derive a lower bound on the Higgs vev $\left\langle H\right\rangle\gtrsim \Lambda_{\text{QCD}}$ which is required by the absence of AdS vacua in lower dimensions. This would explain the relative proximity of the EW and hadronic scales in the SM. The lowest number of quark/lepton generations in which this need for a Higgs applies is three, giving a justification for family replication. We also reassess the connection between the EW scale, neutrino masses and the c.c. in this approach. The EW finetuning is here related to the proximity between the c.c. scale $\Lambda_4^{1/4}$ and the lightest neutrino mass $m_{\nu_i}$ by the expression $ \frac {\Delta H}{H} \lesssim \frac {(a\Lambda_4^ {1/4} m_{\nu_i})} {m_{\nu_i}}. $

On Neutrino Mixing in Matter and CP and T Violation Effects in Neutrino Oscillations
arXiv:1806.09112 SISSA 23/2018/FISI IPMU180112 IPPP/18/47 SISSA232018FISI IPPP1847 Phys.Lett. B785 (2018) 95104
by: Petcov, S.T. (INFN, Trieste) et al.
Abstract: Aspects of 3neutrino mixing and oscillations in vacuum and in matter with constant density are investigated working with a real form of the neutrino Hamiltonian. We find the (approximate) equalities θ23m=θ23 and δm=δ , θ23 ( θ23m ) and δ ( δm ) being respectively the atmospheric neutrino mixing angle and the Dirac CP violation phase in vacuum (in matter) of the neutrino mixing matrix, which are shown to represent excellent approximations for the conditions of the T2K (T2HK), T2HKK, NO ν A and DUNE neutrino oscillation experiments. A new derivation of the known relation sin2θ23msinδm=sin2θ23sinδ is presented and it is used to obtain a correlation between the shifts of θ23 and δ due to the matter effect. A derivation of the relation between the rephasing invariants which determine the magnitude of CP and T violating effects in 3flavour neutrino oscillations in vacuum, JCP , and of the T violating effects in matter with constant density, JTm≡Jm , reported in [1] without a proof, is presented. It is shown that the function F which appears in this relation, Jm=JCPF , and whose explicit form was given in [1] , coincides with the function F˜ in the similar relation Jm=JCPF˜ derived in [2] , although F and F˜ are expressed in terms of different sets of neutrino mass and mixing parameters and have completely different forms.

Weak pion production off the nucleon in covariant chiral perturbation theory
arXiv:1806.09364 Phys.Rev. D98 (2018) 076004
by: Yao, DeLiang (Valencia U.) et al.
Abstract: Weak pion production off the nucleon at low energies has been systematically investigated in manifestly relativistic baryon chiral perturbation theory with explicit inclusion of the $\Delta$(1232) resonance. Most of the involved lowenergy constants have been previously determined in other processes such as pionnucleon elastic scattering and electromagnetic pion production off the nucleon. For numerical estimates, the few remaining constants are set to be of natural size. As a result, the total cross sections for single pion production on neutrons and protons, induced either by neutrino or antineutrino, are predicted. Our results are consistent with the scarce existing experimental data except in the $\nu_\mu n\to \mu^n\pi^+$ channel, where higherorder contributions might still be significant. The $\Delta$ resonance mechanisms lead to sizeable contributions in all channels, especially in $\nu_\mu p\to \mu^ p\pi^+$, even though the considered energies are close to the production threshold. The present study provides a well founded lowenergy benchmark for phenomenological models aimed at the description of weak pion production processes in the broad kinematic range of interest for current and future neutrinooscillation experiments.

Coherency and incoherency in neutrinonucleus elastic and inelastic scattering
arXiv:1806.08768 Phys.Rev. D98 (2018) 053004
by: Bednyakov, Vadim A. (Dubna, JINR) et al.
Abstract: Neutrinonucleus scattering $\nu A\to \nu A$, in which the nucleus conserves its integrity, is considered. We show that elastic interactions keeping the nucleus in the same quantum state lead to a quadratic enhancement of the corresponding crosssection in terms of the number of nucleons. Meanwhile, the crosssection of inelastic processes in which the quantum state of the nucleus is changed, essentially has a linear dependence on the number of nucleons. These two classes of processes are referred to as coherent and incoherent, respectively. The coherent and incoherent crosssections are driven by factors $F_{p/n}^2$ and $(1F_{p/n}^2)$, where $F_{p/n}^2$ is a proton/neutron formfactor of the nucleus, averaged over its initial states. The coherent crosssection formula used in the literature is revised and corrections depending on kinematics are estimated. As an illustration of the importance of the incoherent channel we considered three experimental setups with different nuclei. Experiments attempting to measure coherent neutrino scattering by solely detecting the recoiling nucleus, as is typical, might be including an incoherent background that is indistinguishable from the signal if the excitation gamma eludes its detection. However, as is shown here, the incoherent component can be measured directly by searching for photons released by the excited nuclei inherent to the incoherent channel. For a beam experiment these gammas should be correlated in time with the beam, and their higher energies make the corresponding signal easily detectable at a rate governed by the ratio of incoherent to coherent crosssections. The detection of signals due to the nuclear recoil and excitation gammas provides a more sensitive instrument in studies of nuclear structure and possible signs of new physics.

Neutrino phenomenology from leptogenesis
arXiv:1806.07615 Eur.Phys.J. C78 (2018) 817
by: Buccella, Franco (INFN, Naples) et al.
Abstract: Assuming a typeI seesaw mechanism for neutrino mass generation and invoking a baryogengesis via leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, similar to uptype quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent DavidsonIbarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a $3\sigma$ range, through the numerical resolution of the leptogenesis Boltzmann equations one gets the following allowed intervals for the lightest neutrino mass and the Dirac CP phase: $0.90\pi<\delta<0.75\pi$ and $m_1\sim( 0.002  0.004)$ eV.

Scientific Works of Shoichi Sakata and Commentaries
by: Maskawa, Toshihide (Nagoya U.)

Lepton Flavor Violating Dilepton Dijet Signatures from Sterile Neutrinos at Proton Colliders
DESY 17151 DESY17151 arXiv:1805.11400 JHEP 1810 (2018) 067
by: Antusch, Stefan (Basel U.) et al.
Abstract: In this article we investigate the prospects of searching for sterile neutrinos in lowscale seesaw scenarios via the lepton flavour violating (but lepton number conserving) dilepton dijet signature. In our study, we focus on the final state $e^\pm \mu^\mp jj$ at the HLLHC and the FCChh (or the SppC). We perform a multivariate analysis at the detector level including the dominant SM backgrounds from ditop, diboson, and triboson. Under the assumption of the activesterile neutrino mixings $V_{ l N}^2=\theta_e^2=\theta_\mu^2$ and $V_{ \tau N}^2 = \theta_\tau^2=0$, the sensitivities on the signal production cross section times branching ratio $\sigma(p p \to l^\pm N)\times {\rm BR} (N \to l^{ \mp} jj)$ and on $V_{ l N}^2$ for sterile neutrino mass $M_N$ between 200 and 1000 GeV are derived. For the benchmark $M_N=500$ GeV, when ignoring systematic uncertainties at the HLLHC (FCChh/SppC) with 3 (20) ${\rm ab}^{1}$ luminosity, the resulting 2$\sigma$ limits on $V_{ l N}^2$ are $4.9\times 10^{3}$ ($7.0\times 10^{5}$), while the 2 $\sigma$ limit on $\sigma \times {\rm BR}$ are $4.4\times10^{2}$ ($1.6\times10^{2}$) fb, respectively. The effect of the systematic uncertainty is also studied and found to be important for sterile neutrinos with smaller masses. We also comment on searches with $\tau^\pm \mu^\mp jj$ and $\tau^\pm e^\mp jj$ final states.

Asymmetric tribimaximal texture
arXiv:1805.10684 Phys.Rev. D98 (2018) 055030
by: Rahat, Moinul Hossain (Florida U.) et al.
Abstract: We construct a texture where the seesaw matrix is diagonalized by the tribimaximal (TBM) matrix with a phase. All angles of the CabibboKobayashiMaskawa matrix and PontecorvoMakiNakagawaSakata matrix are consistent with particle data group values, and the mass relations of quarks and charged leptons extrapolated to the grand unified theory scale are satisfied, including the Gatto relation. The novel ingredient is the asymmetry of the downquark and charged lepton Yukawa matrices. Explaining the reactor angle requires a CP phase in the TBM matrix, resulting in the JarlskogGreenberg invariant at J=0.028, albeit with an undetermined sign. While SO(10) restrains the righthanded neutrino Majorana matrix, the neutrino masses are left undetermined.

Tomography by neutrino pair beam
arXiv:1805.10793 OUHET 973 OUHET973 Phys.Lett. B785 (2018) 536542
by: Asaka, Takehiko (Niigata U.) et al.
Abstract: We consider tomography of the Earth's interior using the neutrino pair beam which has recently been proposed. The beam produces a large amount of neutrino and antineutrino pairs from the circulating partially stripped ions and provides the possibility to measure precisely the energy spectrum of neutrino oscillation probability together with a sufficiently large detector. It is shown that the pair beam gives a better sensitivity to probe the Earth's crust compared with the neutrino sources at present. In addition we present a method to reconstruct a matter density profile by means of the analytic formula of the oscillation probability in which the matter effect is included perturbatively to the second order.

Predictive neutrino mass textures with origin of flavor symmetries
arXiv:1805.07101 EPHOU18004 KIASP18042 APCTP Pre2018  011 Phys.Rev. D98 (2018) 055025
by: Kobayashi, Tatsuo (Hokkaido U.) et al.
Abstract: We investigate origins of predictive onezero neutrino mass textures in a systematic way. Here we search Abelian continuous(discrete) global symmetries, and nonAbelian discrete symmetries, and show how to realize these neutrino masses. Then we propose a concrete model involving a dark matter candidate and an extra gauge boson, and show their phenomenologies.

Invisible Neutrino Decay Could Resolve IceCube’s Track and Cascade Tension
arXiv:1805.05950 Phys.Rev.Lett. 121 (2018) 121802
by: Denton, Peter B. (DARK Cosmology Ctr.) et al.
Abstract: The IceCube Neutrino Observatory detects high energy astrophysical neutrinos in two event topologies: tracks and cascades. Since the flavor composition of each event topology differs, tracks and cascades can be used to test the neutrino properties and the mechanisms behind the neutrino production in astrophysical sources. Assuming a conventional model for the neutrino production, the IceCube data sets related to the two channels are in $>3\sigma$ tension with each other. Invisible neutrino decay with lifetime $\tau/m=10^2$ s/eV solves this tension. Noticeably, it leads to an improvement over the standard nondecay scenario of more than $3\sigma$ while remaining consistent with all other multimessenger observations. In addition, our invisible neutrino decay model predicts a reduction of $59\%$ in the number of observed $\nu_\tau$ events which is consistent with the current observational deficit.

Leptonic $CP$ Violation and Proton Decay in SUSY SO(10)
arXiv:1805.05776 UMDPP01803 JHEP 1809 (2018) 119
by: Mohapatra, Rabindra N. (Maryland U.) et al.
Abstract: We study the correlation between proton lifetime and leptonic CP violation in a class of renormalizable supersymmetric SO(10) grand unified theories (GUTs) with 10, 126 and 120 Higgs fields, which provides a unified description of all fermion masses and a possible resolution for the strong CP problem. This specific model is unique in that it can so far be compatible with current proton lifetime limits for a supersymmetry (SUSY) breaking scale as low as 5 TeV due to the presence of a specific Yukawa texture. Our investigation reveals that a discovery of leptonic CP violation in neutrino oscillations would lead to substantial reduction of the parameter space of the model and the potential ruling out of typeII dominance in the neutrino mass seesaw. Furthermore, the previously predicted proton partial lifetimes are sufficiently long for only certain values of the leptonic CP phase.

Pendulum Leptogenesis
arXiv:1805.04826 OCHAPP351 Phys.Lett. B785 (2018) 184190
by: Bamba, Kazuharu (Fukushima U.) et al.
Abstract: We propose a new nonthermal Leptogenesis mechanism that takes place during the reheating epoch, and utilizes the Ratchet mechanism. The interplay between the oscillation of the inflaton during reheating and a scalar lepton leads to a dynamical system that emulates the wellknown forced pendulum. This is found to produce driven motion in the phase of the scalar lepton which leads to the generation of a nonzero lepton number density that is later redistributed to baryon number via sphaleron processes. This model successfully reproduces the observed baryon asymmetry, while simultaneously providing an origin for neutrino masses via the seesaw mechanism.

Breaking flavor democracy with symmetric perturbations
arXiv:1805.05030 Phys.Lett. B785 (2018) 268273
by: Ghosh, Tathagata (Hawaii U.) et al.
Abstract: Flavor democracy broken in the fermion mass matrix by means of small perturbations can give rise to hierarchical fermion masses. We study the breaking of the $S^L_3 \times S^R_3$ symmetry associated with democratic mass matrices to a smaller exchange symmetry $S^L_2 \times S^R_2$ in the charged lepton, up and down quark sectors. An additional breaking of the $S^L_2 \times S^R_2$ symmetry is necessary for the down quark mass matrix, which yields arbitrary perturbations in that sector. On the other hand, we require the neutrino mass matrix to be diagonal at the leading order, with the perturbations left arbitrary due to the absence of any guiding symmetry. We show that the interplay between these two kinds of perturbations reproduces the quark and lepton mass and mixing observables for either hierarchy of neutrino masses.

Matter effects in neutrino visible decay at future longbaseline experiments
arXiv:1805.03279 Eur.Phys.J. C78 (2018) 809
by: AscencioSosa, M.V. (Lima, Pont. U. Catolica) et al.
Abstract: Neutrino visible decay in the presence of matter is reevaluated. We study these effects in two future longbaseline experiments where matter effects are relevant: DUNE (1300 km) and a hypothetical beam aimed towards ANDES (7650 km). We find that matter effects are negligible for the visible component of neutrino decay at DUNE, being much more relevant at ANDES. We perform a detailed simulation of DUNE, considering $\nu_\mu$ disappearance and $\nu_e$ appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant $\alpha_3$ can be as low as $2\times10^{6}$ eV$^2$ at 90% C.L., depending on the neutrino masses and type of coupling. We also show the impact of neutrino decay in the determination of $\theta_{23}$ and $\delta_{\rm CP}$, and find that the bestfit value of $\theta_{23}$ can move from a true value at the lower octant towards the higher octant.

Threeloop neutrino masses via new massive gauge bosons from $E_6$ GUT
arXiv:1805.01866 MITH1882 Phys.Rev. D98 (2018) 055028
by: Dutta, Bhaskar (Texas AM) et al.
Abstract: We propose a SU(3)C×SU(2)L×SU(2)N×U(1)Y model arising from E6 grand unified theory. We show that the tiny neutrino masses in this model can be generated at the threeloop involving the SU(2)N gauge bosons. With Yukawa couplings around 0.01 or larger and TeVscale SU(2)N gauge bosons, we show that the neutrino oscillation data can be explained naturally by presenting a concrete benchmark set of input parameters. All new particles are around the TeV scale. Thus our model can be tested at the ongoing/future collider experiments.

Constraining NonCold Dark Matter Models with the Global 21cm Signal
arXiv:1805.00021 Phys.Rev. D98 (2018) 063021
by: Schneider, Aurel (ETH, Zurich (main))
Abstract: Any particle dark matter (DM) scenario featuring a suppressed power spectrum of astrophysical relevance results in a delay of galaxy formation. As a consequence, such scenarios can be constrained using the global 21cm absorption signal initiated by the UV radiation of the first stars. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported the first detection of such an absorption signal at redshift $\sim 17$. While its amplitude might indicate the need for new physics, we solely focus on the timing of the signal to test noncold DM models. Assuming conservative limits for the stellartobaryon fraction ($f_{*}<0.03$) and for the minimum cooling temperature ($T_{\rm vir}>10^3$ Kelvin) motivated by radiationhydrodynamic simulations, we are able to derive unprecedented constraints on a variety of noncold DM models. For example, the mass of thermal warm DM is limited to $m_{\rm TH}>6.1$ keV, while mixed DM scenarios (featuring a cold and a hot component) are constrained to a hot DM fraction below 17 percent. The ultralight axion DM model is limited to masses $m_{a}>8\times10^{21}$ eV, a regime where its wavelike nature is pushed far below the kiloparsec scale. Finally, sterile neutrinos from resonant production can be fully disfavoured as a dominant DM candidate. The results of this paper show that the 21cm absorption signal is a powerful discriminant of noncold dark matter, allowing for significant improvements over to the strongest current limits. Confirming the result from EDGES is paramount in this context.

Hybrid seesaw leptogenesis and TeV singlets
arXiv:1804.06847 UMDPP01801 Phys.Lett. B785 (2018) 489497
by: Agashe, Kaustubh (Maryland U.) et al.
Abstract: The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. In this work we propose a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. We show that this structure achieves the goal of filling both the above gaps with couplings of order unity. The necessary structure automatically arises embedding the seesaw mechanism in composite Higgs models, but may also be enforced by new gauge symmetries in a weaklycoupled theory. Our hybrid seesaw models have distinguishing features compared to the standard high scale typeI seesaw and inverse seesaw. Firstly, they have much richer phenomenology. Indeed, they generally predict new TeV scale physics (including scalars) potentially accessible at present and future colliders, whereas weaklycoupled versions may also have cosmological signature due to the presence of a light Nambu–Goldstone boson coupled to neutrinos. Secondly, our scenario features an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses beyond the usual ∼109–1015GeV , without large hierarchies in the Yukawa couplings nor small mass splitting among the singlets.

R(D$^{(∗)}$) from W$^{′}$ and righthanded neutrinos
arXiv:1804.04642 LCTP1811 MITP18028 MITP/18028 JHEP 1809 (2018) 169
by: Greljo, Admir (U. Mainz, PRISMA) et al.
Abstract: We provide an ultraviolet (UV) complete model for the R(D$^{(∗)}$) anomalies, in which the additional contribution to semitauonic b → c transitions arises from decay to a righthanded sterile neutrino via exchange of a TeVscale SU(2)$_{L}$ singlet W$^{′}$. The model is based on an extension of the Standard Model (SM) hypercharge group, U(1)$_{Y}$ , to the SU(2)$_{V}$ × U(1)$^{′}$ gauge group, containing several pairs of heavy vectorlike fermions. We present a comprehensive phenomenological survey of the model, ranging from the lowenergy flavor physics, direct searches at the LHC, to neutrino physics and cosmology. We show that, while the W$^{′}$ and Z$^{′}$induced constraints are important, it is possible to find parameter space naturally consistent with all the available data. The sterile neutrino sector also offers rich phenomenology, including possibilities for measurable dark radiation, gamma ray signals, and displaced decays at colliders.

A singlet doublet dark matter model with radiative neutrino masses
MSTP1805 arXiv:1804.03384 JHEP 1810 (2018) 055
by: Esch, Sonja (Munster U., ITP) et al.
Abstract: We present a detailed study of a combined singletdoublet scalar and singletdoublet fermion model for dark matter. These models have only been studied separately in the past. We show that their combination allows for the radiative generation of neutrino masses, but that it also implies the existence of leptonflavour violating (LFV) processes. We first analyse the dark matter, neutrino mass and LFV aspects separately. We then perform two random scans for scalar dark matter imposing Higgs mass, relic density and neutrino mass constraints, one over the full parameter space, the other over regions where scalarfermion coannihilations become important. In the first case, a large part of the new parameter space is excluded by LFV, and the remaining models will be probed by XENONnT. In the second case, direct detection cross sections are generally too small, but a substantial part of the viable models will be tested by future LFV experiments. Possible constraints from the LHC are also discussed.

Naumov and Toshevlike relations in the renormalizationgroup evolution of quarks and Dirac neutrinos
arXiv:1804.01925 Chin.Phys. C42 (2018) 103105
by: Xing, Zhizhong (Beijing, Inst. High Energy Phys.) et al.
Abstract: In an analytical way of studying matter effects on neutrino oscillations, the Naumov and Toshev relations have been derived to respectively link the Jarlskog invariant of CP violation and the Dirac phase in the standard parametrization of the $3\times 3$ flavor mixing matrix to their mattercorrected counterparts. Here we show that there exist similar relations for Dirac neutrinos and charged leptons evolving with energy scales via the oneloop renormalizationgroup (RG) equations in the taudominance approximation, and for the running behaviors of up and downtype quarks in the topdominance approximation, provided a different parametrization is taken into account.

Natural Alignment of Quark Flavors and Radiatively Induced Quark Mixings
arXiv:1804.01598 UMDPP01802 Phys.Rev. D98 (2018) 073002
by: Dev, Abhish (Maryland U.) et al.
Abstract: The standard model does not provide an explanation of the observed alignment of quark flavors i.e. why are the up and down quarks approximately aligned in their weak interactions according to their masses? We suggest a resolution of this puzzle using a combination of leftright and PecceiQuinn (PQ) symmetry. The quark mixings in this model vanish at the tree level and arise out of one loop radiative corrections which explain their smallness. The lepton mixings, on the other hand, appear at the tree level and are therefore larger. We show that all fermion masses and mixings can be fitted with a reasonable choice of parameters. The neutrino mass fit using seesaw mechanism requires the righthanded WR mass bigger than 18 TeV. Due to the presence of PQ symmetry, this model clearly provides a solution to the strong CP problem.

Looking for the left sneutrino LSP with displacedvertex searches
arXiv:1804.00067 Phys.Rev. D98 (2018) 075004
by: Lara, Iñaki (Madrid, IFT) et al.
Abstract: We analyze a displaced dilepton signal expected at the LHC for a tau left sneutrino as the lightest supersymmetric particle with a mass in the range 45–100 GeV. The sneutrinos are pair produced via a virtual W, Z or γ in the s channel and, given the large value of the tau Yukawa coupling, their decays into two dileptons or a dilepton plus missing transverse energy from neutrinos can be significant. The discussion is carried out in the framework of the μνSSM, where the presence of Rparity violating couplings involving righthanded neutrinos solves the μ problem and can reproduce the neutrino data. To probe the tau left sneutrinos we compare the predictions of this scenario with the ATLAS search for longlived particles using displaced lepton pairs in pp collisions at s=8 TeV, allowing us to constrain the parameter space of the model. We also consider an optimization of the trigger requirements used in existing displacedvertex searches by means of a high level trigger that exploits tracker information. This optimization is generically useful for a light metastable particle decaying into soft charged leptons. The constraints on the sneutrino turn out to be more stringent. We finally discuss the prospects for the 13 TeV LHC searches as well as further potential optimizations.

Modifications to the neutrino mixing from the μ  τ reflection symmetry
arXiv:1803.04603 Nucl.Phys. B935 (2018) 129143
by: Zhao, Zhenhua (Liaoning Normal U.)
Abstract: The μ  τ reflection symmetry serves as a unique basis for understanding the observed neutrino mixing as it can lead us to the interesting results θ23=π/4 and δ=−π/2 which stand close to the current experimental results. But a precise measurement for θ23 and δ will probably force us to modify the neutrino mixing U(0) from such a symmetry. Here we perform a study for modifications to U(0) in the forms of U(1)†U(0) and U(0)U(1) where U(1)=Rij(1) (for ij=12,23 and 13) with Rij(1) denoting a real orthogonal rotation on the ij plane.

IceCube bounds on sterile neutrinos above 10 eV
arXiv:1803.02362 FTUAM187 IFTUAM/CSIC18023 SISSA 09/2018/FISI Eur.Phys.J. C78 (2018) 807
by: Blennow, Mattias (Madrid, IFT) et al.
Abstract: We study the capabilities of IceCube to search for sterile neutrinos with masses above 10 eV by analyzing its $\nu_\mu$ disappearance atmospheric neutrino sample. We find that IceCube is not only sensitive to the mixing of sterile neutrinos to muon neutrinos, but also to the more elusive mixing with tau neutrinos through matter effects. The currently released 1year data shows a mild (around 2$\sigma$) preference for nonzero sterile mixing, which overlaps with the favoured region for the sterile neutrino interpretation of the ANITA upward shower. Although the null results from CHORUS and NOMAD on $\nu_\mu$ to $\nu_\tau$ oscillations in vacuum disfavour the hint from the IceCube 1year data, the relevant oscillation channel and underlying physics are different. At the $99\%$ C.L. an upper bound is obtained instead that improves over the present SuperKamiokande and DeepCore constraints in some parts of the parameter space. We also investigate the physics reach of the roughly 8 years of data that is already on tape as well as a forecast of 20 years data to probe the present hint or improve upon current constraints.

The first $\Delta(27)$ flavor 331 model with low scale seesaw mechanism
arXiv:1803.01636 Eur.Phys.J. C78 (2018) 804
by: Cárcamo Hernández, A.E. (Santa Maria U., Valparaiso) et al.
Abstract: We propose a viable model based on the $SU(3)_C\times SU(3)_L\times U(1)_X$ gauge group, augmented by the $U(1)_{L_g}$ global lepton number symmetry and the $\Delta(27) \times Z_3\times Z_{16}$ discrete group, capable of explaining the Standard Model (SM) fermion masses and mixings, and having a low scale seesaw mechanism which can be tested at the LHC. In addition the model provides an explanation for the SM fermion masses and mixings. In the proposed model, small masses for the light active neutrinos are generated by an inverse seesaw mechanism caused by non renormalizable Yukawa operators and mediated by three very light Majorana neutrinos and the observed hierarchy of the SM fermion masses and mixing angles is produced by the spontaneous breaking of the $\Delta(27) \times Z_{3}\times Z_{16}$ symmetry at very large energy scale. This neutrino mass generation mechanism is not presented in our previous 331 models with $\Delta(27)$ group (Nucl.Phys. B913 (2016) 792814 and Eur.Phys.J. C76 (2016) no.5, 242), where the masses of the light active neutrinos arise from a combination of type I and type II seesaw mechanisms (Nucl.Phys. B913 (2016) 792814) as well as from a double seesaw mechanism (Eur.Phys.J. C76 (2016) no.5, 242). Thus, this work corresponds to the first implementation of the $\Delta(27)$ symmetry in a 331 model with low scale seesaw mechanism.

Investigation of Dark Matter in the 3231 Model
arXiv:1802.10402 Phys.Rev. D98 (2018) 055033
by: Huong, D.T. (Hanoi Ed. U.) et al.
Abstract: We prove that the $SU(3)_C\otimes SU(2)_L \otimes SU(3)_R\otimes U(1)_X$ (3231) gauge model always contains a matter parity $W_P=(1)^{3(BL)+2s}$ as conserved residual gauge symmetry, where $BL=2(\beta T_{8R}+X)$ is a $SU(3)_R\otimes U(1)_X$ charge. Due to the nonAbelian nature of $BL$, the $W$odd and $W$even fields are actually unified in gauge multiplets. We investigate two viable versions for dark matter according to $\beta=\pm1/\sqrt{3}$, where the dark matter candidates can be fermion, scalar, or vector fields. We figure out the parameter spaces in the allowed regions of the relic density and direct detection crosssections. Additionally, we examine the neutrino masses induced by the seesaw mechanism along with associated lepton flavor violation processes. The new gauge boson searches at the LEPII and LHC are discussed.

Neutrinoless doublebeta decay with massive scalar emission
arXiv:1802.08019 Phys.Lett. B785 (2018) 354361
by: Blum, Kfir (Weizmann Inst.) et al.
Abstract: Searches for neutrinoless doublebeta decay ( 0ν2β ) place an important constraint on models where light fields beyond the Standard Model participate in the neutrino mass mechanism. While 0ν2β experimental collaborations often consider various massless majoron models, including various forms of majoron couplings and multimajoron finalstate processes, none of these searches considered the scenario where the “majoron” ϕ is not massless, mϕ∼ MeV, of the same order as the Q value of the 0ν2β reaction. We consider this parameter region and estimate 0ν2βϕ constraints for mϕ of order MeV. The constraints are affected not only by kinematical phase space suppression but also by a change in the signal to background ratio charachterizing the search. As a result, 0ν2βϕ constraints for mϕ>0 diminish significantly below the reaction threshold. This has phenomenological implications, which we illustrate focusing on highenergy neutrino telescopes. The spectral shape of highenergy astrophysical neutrinos could exhibit features due to resonant νν→ϕ→νν scattering. Such features fall within the sensitivity range of IceCubelike experiments, if mϕ is of order MeV, making 0ν2βϕ a key complimentary laboratory constraint on the scenario. Our results motivate a dedicated analysis by 0ν2β collaborations, analogous to the dedicated analyses targeting massless majoron models.

Hydrodynamical Neutronstar Kicks in Electroncapture Supernovae and Implications for the CRAB Supernova
arXiv:1802.05274 Astrophys.J. 865 (2018) 61
by: Gessner, Alexandra (Dresden, Max Planck Inst.) et al.
Abstract: Neutron stars (NSs) obtain kicks, typically of several 100 km s−1, at birth. The gravitational tugboat mechanism can explain these kicks as consequences of asymmetric mass ejection during the supernova (SN) explosion. Support for this hydrodynamic explanation is provided by observations of SN remnants with associated NSs, which confirm the prediction that the bulk of the explosion ejecta, particularly the chemical elements between silicon and the iron group, are dominantly expelled in the hemisphere opposite to the direction of the NS kick. Here, we present a large set of two and threedimensional explosion simulations of electroncapture SNe, considering explosion energies between ∼3 × 1049 erg and ∼1.6 × 1050 erg. We find that the fast acceleration of the SN shock in the steep density gradient delimiting the O–Ne–Mg core of the progenitor enables such a rapid expansion of neutrinoheated matter that the growth of neutrinodriven convection freezes out quickly in a highmode spherical harmonics pattern. Because the corresponding momentum asymmetry of the ejecta is very small and the gravitational acceleration by the fastexpanding ejecta abates rapidly, the NS kick velocities are a few km s−1, at most. The extremely low core compactness of O–Ne–Mgcore progenitors therefore favors hydrodynamic NS kicks much below the ∼160 km s−1 measured for the Crab pulsar. This suggests either that the Crab Nebula is not the remnant of an electroncapture SN, but rather of a lowmass ironcore progenitor; or that the Crab pulsar was not accelerated by the gravitational tugboat mechanism, but instead received its kick by a nonhydrodynamic mechanism such as, e.g., anisotropic neutrino emission.

Phenomenology of colored radiative neutrino mass model and its implications on cosmicray observations
arXiv:1802.05248 Chin.Phys. C42 (2018) 103101
by: Ding, Ran (Peking U., CHEP) et al.
Abstract: We extend the colored ZeeBabu model with a gauged $U(1)_{BL}$ symmetry and a scalar singlet dark matter (DM) candidate $S$. The spontaneous breaking of $U(1)_{BL}$ leaves a residual $Z_2$ symmetry that stabilizes the DM and generates tiny neutrino mass at the twoloop level with the color seesaw mechanism. After investigating dark matter and flavor phenomenology of this model systematically, we further focus on its imprint on two of cosmicray anomalies: the FermiLAT gammaray excess at the Galactic Center (GCE) and the PeV ultrahigh energy (UHE) neutrino events at the IceCube. We found that the FermiLAT GCE spectrum can be well fitted by DM annihilation into a pair of onshell singlet Higgs mediators while being compatible with the constraints from relic density, direct detections as well as dwarf spheroidal galaxies in the Milky Way. Although the UHE neutrino events at the IceCube could be accounted for by resonance production of a TeVscale leptoquark, the relevant Yukawa couplings have been severely limited by current low energy flavor experiments. We then derive the IceCube limits on the Yukawa couplings by employing its latest 6year data.

Dirac neutrino mixings from hidden μ – τ symmetry
arXiv:1802.02249 Phys.Lett. B785 (2018) 5158
by: Luna Terrazas, Edgar R. (CINVESTAV, IPN) et al.
Abstract: We explore masses and mixings for Dirac neutrinos in models where lepton number is conserved, under the guidance of a hidden, but broken, $\mu\tau$ exchange symmetry, that makes itself evident in the squared hermitian mass matrix. We study the parameter space in the most general theory as allowed by current neutrino oscillation experiment data. By using a general parameterization of the mass matrix which contains only observable parameters we stablish that the amount of breaking of the symmetry is in the range of the atmospheric mass scale, without regard to the neutrino hierarchy, the absolute neutrino mass and the Dirac CP phase. An estimate of the invisible branching ratio for a Higgs boson decaying into Dirac neutrinos, $H\rightarrow\nu\overline{\nu}$ , is given and compared to recent measurements in this context.

Constraints on the sum of the neutrino masses in dynamical dark energy models with $w(z) \geq 1$ are tighter than those obtained in $\Lambda$CDM
arXiv:1801.08553 LCTP1803 NORDITA2018004 IFIC/1802 IFIC1802 Phys.Rev. D98 (2018) 083501
by: Vagnozzi, Sunny (Stockholm U., OKC) et al.
Abstract: We explore cosmological constraints on the sum of the three active neutrino masses $M_{\nu}$ in the context of dynamical dark energy (DDE) models with equation of state (EoS) parametrized as a function of redshift $z$ by $w(z)=w_0+w_a\,z/(1+z)$, and satisfying $w(z)\geq1$ for all $z$. We perform a Bayesian analysis and show that, within these models, the bounds on $M_{\nu}$ \textit{do not degrade} with respect to those obtained in the $\Lambda$CDM case; in fact the bounds are slightly tighter, despite the enlarged parameter space. We explain our results based on the observation that, for fixed choices of $w_0\,,w_a$ such that $w(z)\geq1$ (but not $w=1$ for all $z$), the upper limit on $M_{\nu}$ is tighter than the $\Lambda$CDM limit because of the wellknown degeneracy between $w$ and $M_{\nu}$. The Bayesian analysis we have carried out then integrates over the possible values of $w_0$$w_a$ such that $w(z)\geq1$, all of which correspond to tighter limits on $M_{\nu}$ than the $\Lambda$CDM limit. We find a 95\% confidence level (C.L.) upper bound of $M_{\nu}<0.13\,\mathrm{eV}$. This bound can be compared with $M_{\nu}<0.16\,\mathrm{eV}$ at 95\%~C.L., obtained within the $\Lambda$CDM model, and $M_{\nu}<0.41\,\mathrm{eV}$ at 95\%~C.L., obtained in a DDE model with arbitrary EoS (which allows values of $w < 1$). Contrary to the results derived for DDE models with arbitrary EoS, we find that a dark energy component with $w(z)\geq1$ is unable to alleviate the tension between highredshift observables and direct measurements of the Hubble constant $H_0$. Finally, in light of the results of this analysis, we also discuss the implications for DDE models of a possible determination of the neutrino mass hierarchy by laboratory searches. (abstract abridged)

Indications of an unexpected signal associated with the GW170817 binary neutron star inspiral
arXiv:1801.03585 Astropart.Phys. 103 (2018) 16
by: Fischbach, E. (Purdue U.) et al.
Abstract: We report experimental evidence at the 2.5 σ level for an unexpected signal associated with the GW170817 binary neutron star inspiral. This evidence derives from a laboratory experiment simultaneously measuring the β decay rates of Si32 and Cl36 in a common detector. Whereas the Si32 and Cl36 decay rates show no statistical correlation before or after the inspiral, they are highly correlated (∼95%) in the 5h time interval immediately following the inspiral. If we interpret this correlation as arising from the influence of particles emitted during the inspiral, then we can estimate the mass m x of these particles from the time delay between the gravitywave signal and a peak in the β decay data. We find for particles of energy 10 MeV, m x ≲ 16 eV which includes the neutrino mass region m ν ≲ 2 eV. The latter is based on existing limits for the masses m i of the three known neutrino flavors. Additionally, we find that the correlation is even stronger if we include data in the 80 minute period before the arrival of the gravity wave signal. Given the large number of radionuclides whose decays are being monitored at any given time, we conjecture that other groups may also be in a position to search for statistically suggestive fluctuations of radionuclide decay rates associated with the GW170817 inspiral, and possibly with other future inspirals.

$W^+ W^ H$ production at lepton colliders: a new hope for heavy neutral leptons
arXiv:1712.07621 IPPP17111 IPPP/17/111 Eur.Phys.J. C78 (2018) 795
by: Baglio, Julien (Tubingen U.) et al.
Abstract: We present the first study of the production of a Standard Model Higgs boson at a lepton collider in association with a pair of W bosons, $e^+_{} e^_{} \rightarrow W^+_{} W^_{} H$ , in the inverse seesaw model. Taking into account all relevant experimental and theoretical constraints, we find sizable effects due to the additional heavy neutrinos up to $38\%$ on the total crosssection at a centerofmass energy of 3 TeV, and even up to $66\%$ with suitable cuts. This motivates a detailed sensitivity analysis of the process $e^+_{} e^_{} \rightarrow W^+_{} W^_{} H$ as it could provide a new, very competitive experimental probe of lowscale neutrino mass models.

PArthENoPE reloaded
arXiv:1712.04378 Comput.Phys.Commun. 233 (2018) 237242
by: Consiglio, R. (Naples U.) et al.
Abstract: We describe the main features of a new and updated version of the program PArthENoPE , which computes the abundances of light elements produced during Big Bang Nucleosynthesis. As the previous first release in 2008, the new one, PArthENoPE2.0 , is publicly available and distributed from the code site, http://parthenope.na.infn.it . Apart from minor changes, which will be also detailed, the main improvements are as follows. The powerful, but not freely accessible, NAG routines have been substituted by ODEPACK libraries, without any significant loss in precision. Moreover, we have developed a Graphical User Interface (GUI) which allows a friendly use of the code and a simpler implementation of running for grids of input parameters.

Dark matter assisted Dirac leptogenesis and neutrino mass
arXiv:1712.02960 Nucl.Phys. B936 (2018) 7690
by: Narendra, Nimmala (Indian Inst. Tech., Hyderabad) et al.
Abstract: We propose an extension of the standard model with U(1)B–L×Z2 symmetry. In this model by assuming that the neutrinos are Dirac ( i.e. B–L is an exact symmetry), we found a simultaneous solution for non zero neutrino masses and dark matter content of the universe. The observed baryon asymmetry of the universe is also explained using Dirac Leptogenesis, which is assisted by a dark sector, gauged under a U(1)D symmetry. The latter symmetry of the dark sector is broken at a TeV scale and thereby giving mass to a neutral gauge boson ZD . The standard model Zboson mixes with the gauge boson ZD at one loop level and paves a way to detect the dark matter through spin independent elastic scattering at terrestrial laboratories.

Neutrinoless Double Beta Decay and the Baryon Asymmetry of the Universe
arXiv:1711.10432 DOTH1719 CP3ORIGINS2017055 DOTH 17/19 CP3Origins2017055 DNRF90 Phys.Rev. D98 (2018) 055029
by: Deppisch, Frank F. (University Coll. London) et al.
Abstract: We discuss the impact of the observation of neutrinoless double beta decay on the washout of lepton number in the early universe. Neutrinoless double beta decay can be triggered by a large number of mechanisms that can be encoded in terms of standard model effective operators which violate lepton number by two units. We calculate the contribution of such operators to the rate of neutrinoless double beta decay and correlate it with the washout of lepton number induced by the same operators in the early universe. We find that the observation of a nonstandard contribution to neutrinoless double beta decay, i.e., not induced by the standard mass mechanism of light neutrino exchange, would correspond to an efficient washout of lepton number above the electroweak scale for many operators up to mass dimension 11. Combined with standard model sphaleron transitions, this would render many baryogenesis mechanisms at higher scales ineffective.

Multilepton signatures of additional scalar bosons beyond the Standard Model at the LHC
arXiv:1711.07874 J.Phys. G45 (2018) 115003
by: von Buddenbrock, Stefan (U. Witwatersrand, Johannesburg, Sch. Phys.) et al.
Abstract: Following a prediction made in Refs.~\cite{vonBuddenbrock:2015ema,Kumar:2016vut,vonBuddenbrock:2016rmr}, this paper focuses on multilepton signatures arising from two new hypothetical scalar bosons, $H$ and $S$, at the Large Hadron Collider (LHC). These two new bosons are an extension to the Standard Model (SM) and interact with the SM Higgs boson, $h$. We consider two production modes for $H$, one being gluon fusion and the other being in association with top quarks. The $H \to S h$ decay mode is considered, where leptonic final states are studied. The CP properties of $S$ are characterised by considering effective couplings derived from dimension six operators through $SWW$ vertices. The nature of the $S$ boson is considered in two separate contexts. Firstly in a simplified model, it is considered to have Higgslike couplings. Secondly, we consider a heavy neutrino model and its interactions with the $Z, W$ and $S$ bosons. The predictions of the models are compared both to ATLAS and CMS results at $\sqrt{s} = 8$ and $13$~TeV, where appropriate. The data is interpreted using a simplified model where all the signal comes from $H \to S h$, assuming $S$ to be Higgslike, $m_H=270$~GeV and $m_S=150$~GeV. The combined result yields gives a best fit value for the parameter $\beta_g$ (the strength of the Yukawa coupling of $H$ to top quarks), $\beta_g^2=1.38\pm 0.22$. A number of regions of the phase space are suggested to the experiments for further exploration.

Challenges posed by nonstandard neutrino interactions in the determination of $\delta_{CP}$ at DUNE
arXiv:1711.04840 Nucl.Phys. B936 (2018) 91105
by: Deepthi, K.N. (Ahmedabad, Phys. Res. Lab) et al.
Abstract: One of the primary objectives of the Deep Underground Neutrino Experiment (DUNE) is to discover the leptonic CP violation and to identify its source. In this context, we study the impact of nonstandard neutrino interactions (NSIs) on observing the CP violation signal at DUNE. We explore the impact of various parameter degeneracies introduced by nonzero NSI and identify which of these can influence the CP violation sensitivity and CP precision of DUNE, by considering NSI both in data and in theory. In particular, we study how the CP sensitivity of DUNE is affected because of the intrinsic hierarchy degeneracy which occurs when the diagonal NSI parameter ϵee=−1 and δCP=±90° .

Probing Leptogenesis at Future Colliders
arXiv:1710.03744 JHEP 1809 (2018) 124
by: Antusch, Stefan (Basel U.) et al.
Abstract: We investigate the question whether leptogenesis, as a mechanism for explaining the baryon asymmetry of the universe, can be tested at future colliders. Focusing on the minimal scenario of two righthanded neutrinos, we identify the allowed parameter space for successful leptogenesis in the heavy neutrino mass range between 5 and 50 GeV. Our calculation includes the lepton flavour violating contribution from heavy neutrino oscillations as well as the lepton number violating contribution from Higgs decays to the baryon asymmetry of the universe. We confront this parameter space region with the discovery potential for heavy neutrinos at future lepton colliders, which can be very sensitive in this mass range via displaced vertex searches. Beyond the discovery of heavy neutrinos, we study the precision at which the flavourdependent activesterile mixing angles can be measured. The measurement of these mixing angles at future colliders can test whether a minimal type I seesaw mechanism is the origin of the light neutrino masses, and it can be a first step towards probing leptogenesis as the mechanism of baryogenesis. We discuss how a stronger test could be achieved with an additional measurement of the heavy neutrino mass difference.

Light scalars and dark photons in Borexino and LSND experiments
arXiv:1706.00424 Phys.Lett. B785 (2018) 288295
by: Pospelov, Maxim (Perimeter Inst. Theor. Phys.) et al.
Abstract: Bringing an external radioactive source close to a large underground detector can significantly advance sensitivity not only to sterile neutrinos but also to “dark” gauge bosons and scalars. Here we address in detail the sensitivity reach of the BorexinoSOX configuration, which will see a powerful (a few PBq) 144 Ce– 144 Pr source installed next to the Borexino detector, to light scalar particles coupled to the SM fermions. The mass reach of this configuration is limited by the energy release in the radioactive γ cascade, which in this particular case is 2.2 MeV. Within that reach one year of operations will achieve an unprecedented sensitivity to coupling constants of such scalars, reaching down to g∼10−7 levels and probing significant parts of parameter space not excluded by either beam dump constraints or astrophysical bounds. Should the current proton charge radius discrepancy be caused by the exchange of a MeVmass scalar, then the simplest models will be decisively probed in this setup. We also update the beam dump constraints on light scalars and vectors, and in particular rule out dark photons with masses below 1 MeV, and couplings ϵ≥10−5 .
