Search

The Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) aims to detect atmospheric neutrinos and antineutrinos separately in the multi-GeV range of energies and over a wide range of baselines. By utilizing its charge identification capability, ICAL can efficiently distinguish $\mu^-$ and $\mu^+$ events. Atmospheric neutrinos passing long distances through Earth can be detected at ICAL with good resolution in energy and direction, which enables ICAL to see the density-dependent matter oscillations experienced by upward-going neutrinos in the multi-GeV range of energies. In this work, we explore the possibility of utilizing neutrino oscillations in the presence of matter to extract information about the internal structure of Earth complementary to seismic studies. Using good directional resolution, ICAL would be able to observe 331 $\mu^-$ and 146 $\mu^+$ core-passing events with 500 kt$\cdot$yr exposure. With this exposure, we show for the first time that the presence of Earth's core can be independently confirmed at ICAL with a median $\Delta \chi^2$ of 7.45 (4.83) assuming normal (inverted) mass ordering by ruling out the simple two-layered mantle-crust profile in theory while generating the prospective data with the PREM profile. We observe that in the absence of charge identification capability of ICAL, this sensitivity deteriorates significantly to 3.76 (1.59) for normal (inverted) mass ordering., Comment: 29 pages, 7 figures, 7 tables. Published in JHEP. Matches with the published version

Models of gauged U 1 L μ − L τ $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$ can provide a solution to the long-standing discrepancy between the theoretical prediction for the muon anomalous magnetic moment and its measured value. The extra contribution is due to a new light vector mediator, which also helps to alleviate an existing tension in the determination of the Hubble parameter. In this article, we explore ways to probe this solution via the scattering of solar neutrinos with electrons and nuclei in a range of experiments and considering high and low solar metallicity scenarios. In particular, we reevaluate Borexino constraints on neutrino-electron scattering, finding them to be more stringent than previously reported, and already excluding a part of the (g − 2) μ explanation with mediator masses smaller than 2 × 10 −2 GeV. We then show that future direct dark matter detectors will be able to probe most of the remaining solution. Due to its large exposure, LUX-ZEPLIN will explore regions with mediator masses up to 5 × 10 −2 GeV and DARWIN will be able to extend the search beyond 10 −1 GeV, thereby covering most of the area compatible with (g − 2) μ . For completeness, we have also computed the constraints derived from the recent XENON1T electron recoil search and from the CENNS-10 LAr detector, showing that none of them excludes new areas of the parameter space. Should the excess in the muon anomalous magnetic moment be confirmed, our work suggests that direct detection experiments could provide crucial information with which to test the U 1 L μ − L τ $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$ solution, complementary to efforts in neutrino experiments and accelerators.

Long-lived particles are predicted in extensions of the Standard Model that involve relatively light but very weakly interacting sectors. In this paper we consider the possibility that some of these particles are produced in atmospheric cosmic ray showers, and their decay intercepted by neutrino detectors such as IceCube or Super-Kamiokande. We present the methodology and evaluate the sensitivity of these searches in various scenarios, including extensions with heavy neutral leptons in models of massive neutrinos, models with an extra $U(1)$ gauge symmetry, and a combination of both in a $U(1)_{B-L}$ model. Our results are shown as a function of the production rate and the lifetime of the corresponding long-lived particles., Comment: 33 pages, 19 figures. v2: Minor changes, references added. Version accepted for publication in JHEP

Sterile neutrinos with keV-MeV masses and non-zero transition magnetic moments can be probed through low-energy nuclear or electron recoil measurements. Here we determine the sensitivities of current and future searches, showing how they can probe a previously unexplored parameter region. Future coherent elastic neutrino-nucleus scattering (CE$\nu$NS) or elastic neutrino-electron scattering (E$\nu$ES) experiments using a monochromatic $^{51}$Cr source can fully probe the region indicated by the recent XENON1T excess., Comment: 22 pages, 4 figures, 2 tables. V2: References added, Fig.3 updated with additional bounds, conclusions unchanged, matches the published version

We perform a global analysis of neutrino data in the framework of three massive neutrinos with non-standard neutrino interactions which affect their evolution in the matter background. We focus on the effect of NSI in the present observables sensitive to leptonic CP violation and to the mass ordering. We consider complex neutral current neutrino interactions with quarks whose lepton-flavor structure is independent of the quark type. We quantify the status of the "hints" for CP violation, the mass-ordering and non-maximality of θ23 in these scenarios. We also present a parametrization-invariant formalism for leptonic CP violation in presence of a generalized matter potential induced by NSI., This work is supported by USA-NSF grant PHY-1620628, by EU Networks FP10 ITN ELUSIVES (H2020-MSCA-ITN-2015-674896) and INVISIBLES-PLUS (H2020-MSCA-RISE-2015-690575), by MINECO grant FPA2016-76005-C2-1-P and MINECO/FEDER-UE grants FPA2015-65929-P and FPA2016-78645-P, by Maria de Maetzu program grant MDM-2014-0367 of ICCUB, and by the "Severo Ochoa" program grant SEV-2016-0597 of IFT. I.E. acknowledges support from the FPU program fellowship FPU15/03697.

We propose a $\mu-\tau$ reflection symmetric Littlest Seesaw ($\mu\tau$-LSS) model. In this model the two mass parameters of the LSS model are fixed to be in a special ratio by symmetry, so that the resulting neutrino mass matrix in the flavour basis (after the seesaw mechanism has been applied) satisfies $\mu-\tau$ reflection symmetry and has only one free adjustable parameter, namely an overall free mass scale. However the physical low energy predictions of the neutrino masses and lepton mixing angles and CP phases are subject to renormalisation group (RG) corrections, which introduces further parameters. Although the high energy model is rather complicated, involving $(S_4\times U(1))^2$ and supersymmetry, with many flavons and driving fields, the low energy neutrino mass matrix has ultimate simplicity., Comment: 26 pages, 1 figure, discussions and references added, accepted for publication in JHEP

The millicharged particle has become an attractive topic to probe physics beyond the Standard Model. In direct detection experiments, the parameter space of millicharged particles can be constrained from the atomic ionization process. In this work, we develop the relativistic impulse approximation (RIA) approach, which can duel with atomic many-body effects effectively, in the atomic ionization process induced by millicharged particles. The formulation of RIA in the atomic ionization induced by millicharged particles is derived, and the numerical calculations are obtained and compared with those from free electron approximation and equivalent photon approximation. Concretely, the atomic ionizations induced by mllicharged dark matter particles and millicharged neutrinos in high-purity germanium (HPGe) and liquid xenon (LXe) detectors are carefully studied in this work. The differential cross sections, reaction event rates in HPGe and LXe detectors, and detecting sensitivities on dark matter particle and neutrino millicharge in next-generation HPGe and LXe based experiments are estimated and calculated to give a comprehensive study. Our results suggested that the next-generation experiments would improve 2-3 orders of magnitude on dark matter particle millicharge $\delta_{\chi}$ than the current best experimental bounds in direct detection experiments. Furthermore, the next-generation experiments would also improve 2-3 times on neutrino millicharge $\delta_{\nu}$ than the current experimental bounds., Comment: 60 pages, 14 figures, 2 tables; Some typos are corrected in V2, more physical discussions are presented in V3, and V4 is the published version

Cosmic-ray interactions with the solar atmosphere are expected to produce particle showers which in turn produce neutrinos from weak decays of mesons. These solar atmospheric neutrinos (SAνs) have never been observed experimentally. A detection would be an important step in understanding cosmic-ray propagation in the inner solar system and the dynamics of solar magnetic fields. SAνs also represent an irreducible background to solar dark matter searches and a detection would allow precise characterization of this background. Here, we present the first experimental search based on seven years of data collected from May 2010 to May 2017 in the austral winter with the IceCube Neutrino Observatory. An unbinned likelihood analysis is performed for events reconstructed within 5 degrees of the center of the Sun. No evidence for a SAν flux is observed. After inclusion of systematic uncertainties, we set a 90% upper limit of 1.02+0.20-0.18·10-13 GeV-1cm-2s-1 at 1 TeV.

Neutrino flavour transmutations in nonuniform matter are described by a Schr\"{o}dinger-like evolution equation with coordinate-dependent potential. In all the derivations of this equation it is assumed that the potential, which is due to coherent forward scattering of neutrinos on matter constituents, is a continuous function of coordinate that changes slowly over the distances of the order of the neutrino de Broglie wavelength. This tacitly assumes that some averaging of the microscopic potential (which takes into account the discrete nature of the scatterers) has been performed.The averaging, however, must be applied to the microscopic evolution equation as a whole and not just to the potential. Such an averaging has never been explicitly carried out. We fill this gap by considering the transition from the microscopic to macroscopic neutrino evolution equation through a proper averaging procedure. We discuss some subtleties related to this procedure and establish the applicability domain of the standard macroscopic evolution equation. This, in particular, allows us to answer the question of when neutrino propagation in rarefied media (such as e.g.\ low-density gases or interstellar or intergalactic media) can be considered within the standard theory of neutrino flavour evolution in matter., Comment: LaTeX, 20 pages. v2: a section on media with bulk currents and magnetization and an appendix section added; section 2 modified accordingly; reference added

We quantify the effect of gauge bosons from a weakly coupled lepton flavor dependent U(1)' interaction on the matter background in the evolution of solar, atmospheric, reactor and long-baseline accelerator neutrinos in the global analysis of oscillation data. The analysis is performed for interaction lengths ranging from the Sun-Earth distance to effective contact neutrino interactions. We survey ~10000 set of models characterized by the six relevant fermion U(1)' charges and find that in all cases, constraints on the coupling and mass of the Z' can be derived. We also find that about 5% of the U(1)' model charges lead to a viable LMA-D solution but this is only possible in the contact interaction limit. We explicitly quantify the constraints for a variety of models including U(1) B - 3Le, U(1) B - 3Lµ, U(1) B - 3Lτ, U(1) B - 3/2 (Lµ+Lτ) , U(1) Le - Lµ , U(1) Le - Lτ , U(1) Le - 1/2 (Lµ+Lτ). We compare the constraints imposed by our oscillation analysis with the strongest bounds from fifth force searches, violation of equivalence principle as well as bounds from scattering experiments and white dwarf cooling. Our results show that generically, the oscillation analysis improves over the existing bounds from gravity tests for Z' lighter than ∼ 1e-8 → 1e-11 eV depending on the specific couplings. In the contact interaction limit, we find that for most models listed above there are values of g' and MZ' for which the oscillation analysis provides constraints beyond those imposed by laboratory experiments. Finally we illustrate the range of Z' and couplings leading to a viable LMA-D solution for two sets of models., The authors acknowledge use of the HPC facilities at the IFT (Hydra cluster). This work was supported by the Spanish grants FPA2016-76005-C2-1-P, FPA2016-78645-P, PID2019-105614GB-C21 and PID2019-110058GB-C21, by EU Network FP10 ITN HIDDEN (H2020-MSCA-ITN-2019-860881), by USA-NSF grant PHY-1915093, by AGAUR (Generalitat de Catalunya) grant 2017-SGR-929. The authors acknowledge the support of the Spanish Agencia Estatal de Investigación through the grant “IFT Centro de Excelencia Severo Ochoa SEV-2016-0597”. PC acknowledges funding from the Spanish MICINN through the “Ramon y Cajal” program under grant RYC2018-024240-I.

With large active volume sizes dark matter direct detection experiments are sensitive to solar neutrino fluxes. Nuclear recoil signals are induced by $^8$B neutrinos, while electron recoils are mainly generated by the pp flux. Measurements of both processes offer an opportunity to test neutrino properties at low thresholds with fairly low backgrounds. In this paper we study the sensitivity of these experiments to neutrino magnetic dipole moments assuming 1, 10 and 40 tonne active volumes (representative of XENON1T, XENONnT and DARWIN), 0.3 keV and 1 keV thresholds. We show that with nuclear recoil measurements alone a 40 tonne detector could be as competitive as Borexino, TEXONO and GEMMA, with sensitivities of order $8.0\times 10^{-11}\,\mu_B$ at the $90\%$ CL after one year of data taking. Electron recoil measurements will increase sensitivities way below these values allowing to test regions not excluded by astrophysical arguments. Using electron recoil data and depending on performance, the same detector will be able to explore values down to $4.0\times 10^{-12}\mu_B$ at the $90\%$ CL in one year of data taking. By assuming a 200-tonne liquid xenon detector operating during 10 years, we conclude that sensitivities in this type of detectors will be of order $10^{-12}\,\mu_B$. Reducing statistical uncertainties may enable improving sensitivities below these values., Comment: 9 pages, 5 figures

Right-handed neutrinos ($\nu_{R}$) are often considered as a portal to new hidden physics. It is tempting to consider a gauge singlet scalar $(\phi)$ that exclusively couples to $\nu_{R}$ via a $\nu_{R}\nu_{R}\phi$ term. Such a $\nu_{R}$-philic scalar does not interact with charged fermions at tree level but loop-induced effective interactions are inevitable, which are systematically investigated in this work. The magnitude of the loop-induced couplings coincidentally meets the current sensitivity of fifth-force searches. In particular, the loop-induced coupling to muons could be tested in the recent LIGO observations of neutron star mergers as there might be a sizable Yukawa force in the binary system mediated by the $\nu_{R}$-philic scalar., Comment: 24 pages, 5 figures, results of the pseudo-scalar case added, JHEP published version. Code available from https://github. com/xunjiexu/vR_loop

Simultaneous treatment of neutrino oscillations and collisions in astrophysical environments requires the use of (quantum) kinetic equations. Despite major advances in the field of quantum kinetics, the structure of the kinetic equations and their consistency with the uncertainty principle are still debated. The goals of the present work are threefold. First, it clarifies the structure of the Liouville term in the presence of mixing. Second, we derive evolution equation for neutrinos propagating in vacuum or matter from the Schrodinger equation and show that in the relativistic limit its form matches the form of the (collisionless part of the) kinetic equation derived by Sigl and Raffelt. Third, by constructing solutions of the evolution equation from the known solutions of the Schrodinger equation, we show that the former also admits solutions consistent with the uncertainty principle and accounts for neutrino wave packet separation. The obtained results speak in favor of a (quantum) kinetic approach to the analysis of neutrino propagation in exploding supernovae where neutrino oscillations and collisions, as well as the effect of wave packet separation, might be equally important., Comment: 29 pages, matches the published version, title changed, extended discussion of neutrino propagation in matter, appendix added

New physics in neutrino sector can reveal itself via non-standard neutrino interactions which can result in modification of the standard picture of neutrino propagation in matter. Experiments with atmospheric neutrinos has been used to probe this scenario. Using publicly available three-year low energy data in IceCube DeepCore we place bounds on the parameters $\epsilon_{\alpha\beta}$ of non-standard neutrino interactions in propagation. We obtain restrictive constraints not only for $\mu\tau$ sector but also for flavor changing interactions involving electron neutrinos., Comment: 13 pages, 9 figures, study of impact of the systematic uncertainties and improved comparison with experimental results added, bounds unchanged, references added, published version

We perform a global fit to neutrino oscillation and coherent neutrino-nucleus scattering data, using both timing and energy information from the COHERENT experiment. The results are used to set model-independent bounds on four-fermion effective operators inducing non-standard neutral-current neutrino interactions. We quantify the allowed ranges for their Wilson coefficients, as well as the status of the LMA-D solution, for a wide class of new physics models with arbitrary ratios between the strength of the operators involving up and down quarks. Our results are presented for the COHERENT experiment alone, as well as in combination with the global data from oscillation experiments. We also quantify the dependence of our results for COHERENT with respect to the choice of quenching factor, nuclear form factor, and the treatment of the backgrounds., This work was supported by the MINECO grant FPA2016-76005-C2-1-P, by the MINECO FEDER/UE grants FPA2015-65929-P, FPA2016-78645-P and FPA2017-85985-P, by PROMETEO/2019/083, by USA-NSF grants PHY-1620628, by EU Networks FP10 ITN ELUSIVES (H2020-MSCA-ITN-2015-674896) and INVISIBLES-PLUS (H2020-MSCA-RISE-2015-690575), by the “Severo Ochoa” program grant SEV-2016-0597 of IFT and by AGAUR (Generalitat de Catalunya) grant 2017-SGR-929. IE acknowledges support from the FPU program fellowship FPU15/0369.

Neutrino non-standard interactions (NSI) with the first generation of standard model fermions can span a parameter space of large dimension and exhibit degeneracies that cannot be broken by a single class of experiment. Oscillation experiments, together with neutrino scattering experiments, can merge their observations into a highly informational dataset to combat this problem. We consider combining neutrino-electron and neutrino-nucleus scattering data from the Borexino and COHERENT experiments, including a projection for the upcoming coherent neutrino scattering measurement at the CENNS-10 liquid argon detector. We extend the reach of these data sets over the NSI parameter space with projections for neutrino scattering at a future multi-ton scale dark matter detector and future oscillation measurements from atmospheric neutrinos at the Deep Underground Neutrino Experiment (DUNE). In order to perform this global analysis, we adopt a novel approach using the copula method, utilized to combine posterior information from different experiments with a large, generalized set of NSI parameters. We find that the contributions from DUNE and a dark matter detector to the Borexino and COHERENT fits can improve constraints on the electron and quark NSI parameters by up to a factor of 2 to 3, even when relatively many NSI parameters are left free to vary in the analysis., Comment: Published in JHEP. References and plots updated, CENNS-10 analysis updated. Codes can be provided upon request

Future dark matter (DM) direct detection searches will be subject to irreducible neutrino backgrounds that will challenge the identification of an actual WIMP signal in experiments without directionality sensitivity. We study the impact of neutrino-quark non-standard interactions (NSI) on this background, assuming the constraints from neutrino oscillations and the recent COHERENT experiment data, which are relevant for NSI mediated by light mediators, mm e d≲ O(GeV). We calculate the expected number of neutrino-nucleus elastic scattering events in a Xe-based ton-size dark matter detector, including solar neutrino fluxes from the pp chain and CNO cycle as well as sub-GeV atmospheric fluxes and taking into account NSI effects in both propagation and detection. We find that sizable deviations from the standard model expectation are possible, but are more pronounced for flavor-diagonal couplings, in particular for electron neutrinos. We show that neutrino NSI can enhance or deplete the neutrino-nucleus event rate, which may impact DM searches in multi-ton detectors., SCOPUS: ar.j, info:eu-repo/semantics/published

Couplings between light scalar dark matter (DM) and neutrinos induce a perturbation to the neutrino mass matrix. If the DM oscillation period is smaller than ten minutes (or equivalently, the DM particle is heavier than $0.69\times10^{-17}$ eV), the fast-averaging over an oscillation cycle leads to a modification of the measured oscillation parameters. We present a specific $\mu-\tau$ symmetric model in which the measured value of $\theta_{13}$ is entirely generated by the DM interaction, and which reproduces the other measured oscillation parameters. For a scalar DM particle lighter than $10^{-15}$ eV, adiabatic solar neutrino propagation is maintained. A suppression of the sensitivity to CP violation at long-baseline neutrino experiments is predicted in this model. We find that DUNE cannot exclude the DM scenario at more than $3\sigma$ C.L. for bimaximal, tribimaximal and hexagonal mixing, while JUNO can rule it out at more than $6\sigma$ C.L. by precisely measuring both $\theta_{12}$ and $\theta_{13}$., Comment: 21 pages, 2 figures. Version to appear in JHEP

The standard model coherent elastic neutrino-nucleus scattering (CE$\nu$NS) cross section is subject to nuclear form factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. Motivated by COHERENT phases I-III and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. We find that the uncertainties become relevant for momentum transfers $q\gtrsim 20$ MeV and are essentially independent of the form factor parameterization. Consequently, form factor uncertainties are not important for CE$\nu$NS induced by reactor or solar neutrinos. Taking into account these uncertainties, we then evaluate their impact on measurements of CE$\nu$NS at COHERENT, the diffuse supernova background (DSNB) neutrinos and sub-GeV atmospheric neutrinos. We also calculate the relative uncertainties in the number of COHERENT events for different nuclei as a function of recoil energy. For DSNB and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. Finally, we consider the impact of form factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. We point out that studies of new physics using CE$\nu$NS data are affected by neutron form factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. The uncertainties quantified here are also relevant for dark matter direct detection searches., Comment: 13 pages, 7 figures, 1 table. Version to appear in JHEP

The solar neutrino flux arrives at Earth as an incoherent admixture of mass eigenstates, and then solar neutrino detection constitute a blind probe to the oscillation pattern of the neutrino flavour conversion. Consequently, it is also impossible to probe, in a model independent approach, any new physics that leads to an enhancement of decoherence during the neutrino evolution, an effect that is present for instance in Open Quantum System formalism. However, such mechanism can also induce changes between mass eigenstates if an energy interchange between the neutrino subsystem and the reservoir is not explicitly forbidden. In this work the conversion probabilities between mass eigenstates in an Open Quantum System are calculated, and limits are stablished for these kind of transitions. We present our results in a pedagogical way, pointing out how far the analysis can go without any assumption on the neutrino conversion physics inside the Sun, before performing the full calculations. We obtain as limits for the decoherence parameters the values of $ \Gamma_3< 6.5\times 10^{-19}$ eV and $\Gamma_8< 7.1\times 10^{-19}$ eV at 3$\sigma$., Comment: 24 pages, 4 figures

We consider a new Weinberg operator for neutrino mass of the form $H_u\tilde{H_d}L_iL_j$ involving two different Higgs doublets $H_u, H_d$ with opposite hypercharge, where $\tilde{H_d}$ is the charge conjugated doublet. It may arise from a model where the two Higgs doublets carry the same charge under a $U(1)'$ gauge group which forbids the usual Weinberg operator but allows the mixed one. The new Weinberg operator may be generated via two right-handed neutrinos oppositely charged under the $U(1)'$, which may be identified as components of a fourth vector-like family in a complete model. Such a version of the type I seesaw model, which we refer to as type Ib to distinguish it from the usual type Ia seesaw mechanism which yields the usual Weinberg operator, allows the possibility of having potentially large violations of unitarity of the leptonic mixing matrix whose bounds we explore. We also consider the relaxation of the unitarity bounds due to the further addition of a single right-handed neutrino, neutral under $U(1)'$, yielding a usual type Ia seesaw contribution., 19 pages, 6 figures. v2: minor typos corrected and references added

Recent IceCube search results for sterile neutrino increased tension between the combined appearance and disappearance experiments. On the other hand, MiniBooNE latest data confirms at $4.9\sigma$ CL the short-baseline oscillation anomaly. We analyze published IceCube data based on two different active-sterile mixing schemes using one additional sterile neutrino flavor. We present exclusion regions in the parameter ranges $0.01 \le \sin^2 \theta_{24} \le 0.1$ and $0.1~{\rm eV}^2 \le \Delta m^2_{42} \le 10~{\rm eV}^2$ for the mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing scheme, $3\sigma$ CL allowed regions for the appearance experiment and MiniBooNE latest result are excluded at $\gtrsim 3\sigma$ CL. In case of less-restrictive flavor-mixing scheme, results from the appearance experiments are excluded at $\gtrsim 2\sigma$ CL. We also find that including prompt component of the atmospheric neutrino flux relaxes constraints on sterile mixing for $\Delta m^2_{42} \gtrsim 1~{\rm eV}^2$., Comment: 15 pages and 5 figures. Accepted for publication in JHEP

New physics can emerge at low energy scales, involving very light and very weakly interacting new particles. These particles can mediate interactions between neutrinos and usual matter and contribute to the Wolfenstein potential relevant for neutrino oscillations. We compute the Wolfenstein potential in the presence of ultra-light scalar and vector mediators and study the dependence of the potential on the mediator mass $m_A$, taking the finite size of matter distribution (Earth, Sun, supernovae) into consideration. For ultra-light mediators with $m_{A}^{-1}$ comparable to the size of the medium ($R$), the usual $m_{A}^{-2}$ dependence of the potential is modified. In particular, when $m_{A}^{-1}\gg R$, the potential does not depend on $m_{A}$. Taking into account existing bounds on light mediators, we find that for the scalar case significant effects on neutrino propagation are not possible, while for the vector case large matter effects are allowed for $m_{A} \in [2\times10^{-17}$, $4\times10^{-14}]$ eV and the gauge coupling $g\sim 10^{-25}$., Comment: 12 pages, 2 figures, typos in Eqs.(2), (5), and (23) corrected

Cosmic-ray interactions with the solar atmosphere are expected to produce particle showers which in turn produce neutrinos from weak decays of mesons. These solar atmospheric neutrinos (SAνs) have never been observed experimentally. A detection would be an important step in understanding cosmic-ray propagation in the inner solar system and the dynamics of solar magnetic fields. SAνs also represent an irreducible background to solar dark matter searches and a detection would allow precise characterization of this background. Here, we present the first experimental search based on seven years of data collected from May 2010 to May 2017 in the austral winter with the IceCube Neutrino Observatory. An unbinned likelihood analysis is performed for events reconstructed within 5 degrees of the center of the Sun. No evidence for a SAν flux is observed. After inclusion of systematic uncertainties, we set a 90% upper limit of 1.02+0.20-0.18·10-13 GeV-1cm-2s-1 at 1 TeV., SCOPUS: ar.j, info:eu-repo/semantics/published

We explore the potential of current and next generation of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) experiments in probing neutrino electromagnetic interactions. On the basis of a thorough statistical analysis, we determine the sensitivities on each component of the Majorana neutrino transition magnetic moment (TMM), $\left \vert \Lambda_i \right \vert$, that follow from low-energy neutrino-nucleus experiments. We derive the sensitivity to neutrino TMM from the first CE$\nu$NS measurement by the COHERENT experiment, at the Spallation Neutron Source. We also present results for the next phases of COHERENT using HPGe, LAr and NaI[Tl] detectors and for reactor neutrino experiments such as CONUS, CONNIE, MINER, TEXONO and RED100. The role of the CP violating phases in each case is also briefly discussed. We conclude that future CE$\nu$NS experiments with low-threshold capabilities can improve current TMM limits obtained from Borexino data., Comment: 25 pages, 8 figures, 2 tables, analysis updated; conclusions unchanged; references added; matches published version

We present the results of a global analysis of the neutrino oscillation data available as of fall 2018 in the framework of three massive mixed neutrinos with the goal at determining the ranges of allowed values for the six relevant parameters. We describe the complementarity and quantify the tensions among the results of the different data samples contributing to the determination of each parameter. We also show how those vary when combining our global likelihood with the χ map provided by Super-Kamiokande for their atmospheric neutrino data analysis in the same framework. The best fit of the analysis is for the normal mass ordering with inverted ordering being disfavoured with a Δχ = 4.7 (9.3) without (with) SK-atm. We find a preference for the second octant of θ , disfavouring the first octant with Δχ = 4.4 (6.0) without (with) SK-atm. The best fit for the complex phase is δ = 215° with CP conservation being allowed at Δχ = 1.5 (1.8). As a byproduct we quantify the correlated ranges for the laboratory observables sensitive to the absolute neutrino mass scale in beta decay, mνe , and neutrino-less double beta decay, m , and the total mass of the neutrinos, Σ, which is most relevant in Cosmology., This work is supported by USA-NSF grant PHY-1620628, by EU Networks FP10 ITN ELUSIVES (H2020-MSCA-ITN-2015-674896) and INVISIBLES-PLUS (H2020-MSCA-RISE2015-690575), by MINECO grant FPA2016-76005-C2-1-P and MINECO/FEDER-UE grants FPA2015-65929-P and FPA2016-78645-P, by Maria de Maetzu program grant MDM2014-0367 of ICCUB, and by the “Severo Ochoa” program grant SEV-2016-0597 of IFT. I.E. acknowledges support from the FPU program fellowship FPU15/03697.

We show that the four high-energy Littlest Seesaw parameters in the flavour basis,namely two real Yukawa couplings plus the two right-handed neutrino masses, can be determined by an excellent fit to the seven currently constrained observables of low-energy neutrino data and leptogenesis. Taking into account renormalisation group corrections, we estimate $\chi^2 \simeq 1.5-2.6$ for the three d.o.f., depending on the high-energy scale and the type of non supersymmetric Littlest Seesaw model. We extract allowed ranges of neutrino parameters from our fit data, including the approximate mu-tau symmetric predictions $\theta_{23}=45^o\pm 1^o$ and $\delta = -90^o \pm 5^o $, which, together with a normal mass ordering with $m_1=0$, will enable Littlest Seesaw models to be tested in future neutrino experiments., Comment: Typos corrected, references added. 25 pages, 20 figures

The detection of coherent neutrino-nucleus scattering by the COHERENT collaboration has set on quantitative grounds the existence of an irreducible neutrino background in direct detection searches of Weakly Interacting Massive Dark Matter candidates. This background leads to an ultimate discovery limit for these experiments: a minimum Dark Matter interaction cross section below which events produced by the coherent neutrino scattering will mimic the Dark Matter signal, the so-called \emph{neutrino floor}. In this work we study the modification of such neutrino floor induced by non-standard neutrino interactions within their presently allowed values by the global analysis of oscillation and COHERENT data. By using the full likelihood information of such global analysis we consistently account for the correlated effects of non-standard neutrino interactions both in the neutrino propagation in matter and in its interaction in the detector. We quantify their impact on the neutrino floor for five future experiments: DARWIN (Xe), ARGO (Ar), Super-CDMS HV (Ge and Si) and CRESST phase III (CaWO$_4$). Quantitatively, we find that non-standard neutrino interactions allowed at the $3\sigma$ level can result in an increase of the neutrino floor of up to a factor $\sim 5$ with respect to the Standard Model expectations and impact the expected sensitivities of the ARGO, CRESST phase III and DARWIN experiments., Comment: 21 pages, 4 figures. Matches version published in the JHEP. Corrected exposure and results for CRESST phase III

We study the phenomenological implications of the modular symmetry $\Gamma(3) \simeq A_4$ of lepton flavors facing recent experimental data of neutrino oscillations. The mass matrices of neutrinos and charged leptons are essentially given by fixing the expectation value of modulus $\tau$, which is the only source of modular invariance breaking. We introduce no flavons in contrast with the conventional flavor models with $A_4$ symmetry. We classify our neutrino models along with the type I seesaw model, the Weinberg operator model and the Dirac neutrino model. In the normal hierarchy of neutrino masses, the seesaw model is available by taking account of recent experimental data of neutrino oscillations and the cosmological bound of sum of neutrino masses. The predicted $\sin^2\theta_{23}$ is restricted to be larger than $0.54$ and $\delta_{CP}=\pm (50^{\circ}\mbox{--}180^{\circ})$. Since the correlation of $\sin^2\theta_{23}$ and $\delta_{CP}$ is sharp, the prediction is testable in the future. It is remarkable that the effective mass $m_{ee}$ of the neutrinoless double beta decay is around $22$\,meV while the sum of neutrino masses is predicted to be $145$\,meV. On the other hand, for the inverted hierarchy of neutrino masses, only the Dirac neutrino model is consistent with the experimental data., Comment: 17 pages, 6 figures, 5 tables, major modifications

We investigate the prompt neutrino background at IceCube, as determined from forward charm. We consider the role of intrinsic charm and of a recombination model and show that the contribution of these mechanisms is at most a factor two., Comment: 10 pages, 6 figures; v2: Improved discussion, figures; no changes in results; version accepted for publication in JHEP

We investigate the effect of new physics interacting with both Dark Matter (DM) and neutrinos at DM direct detection experiments. Working within a simplified model formalism, we consider vector and scalar mediators to determine the scattering of DM as well as the modified scattering of solar neutrinos off nuclei. Using existing data from LUX as well as the expected sensitivity of LUX-ZEPLIN and DARWIN, we set limits on the couplings of the mediators to quarks, neutrinos and DM. Given the current limits, we also assess the true DM discovery potential of direct detection experiments under the presence of exotic neutrino interactions. In the case of a vector mediator, we show that the DM discovery reach of future experiments is affected for DM masses $m_\chi \lesssim 10$ GeV or DM scattering cross sections $\sigma_\chi \lesssim 10^{-47}$ cm$^2$. On the other hand, a scalar mediator will not affect the discovery reach appreciably., Comment: One figure, comments and references added. Version published in the JHEP

Cosmic rays interacting in the solar atmosphere produce showers that result in a flux of high-energy neutrinos from the Sun. These form an irreducible background to indirect solar WIMP co-annihilation searches, which look for heavy dark matter particles annihilating into final states containing neutrinos in the Solar core. This background will eventually create a sensitivity floor for indirect WIMP co-annihilation searches analogous to that imposed by low-energy solar neutrino interactions for direct dark matter detection experiments. We present a new calculation of the flux of solar atmospheric neutrinos with a detailed treatment of systematic uncertainties inherent in solar atmospheric shower evolution, and we use this to derive the sensitivity floor for indirect solar WIMP annihilation analyses. We find that the floor lies less than one order of magnitude beyond the present experimental limits on spin-dependent WIMP-proton cross sections for some mass points, and that the high-energy solar atmospheric neutrino flux may be observable with running and future neutrino telescopes., 21 pages, 11 figures

Sterile neutrinos at the eV scale have long been studied in the context of anomalies in short baseline neutrino experiments. Their cosmology can be made compatible with our understanding of the early Universe provided the sterile neutrino sector enjoys a nontrivial dynamics with exotic interactions, possibly providing a link to the Dark Matter (DM) puzzle. Interactions between DM and neutrinos have also been proposed to address the long-standing "missing satellites" problem in the field of large scale structure formation. Motivated by these considerations, in this paper we discuss realistic scenarios with light steriles coupled to DM. We point out that within this framework active neutrinos acquire an effective coupling to DM that manifests itself as a new matter potential in the propagation within a medium of asymmetric DM. Assuming that at least a small fraction of asymmetric DM has been captured by the Sun, we show that a sizable region of the parameter space of these scenarios can be probed by solar neutrino experiments, especially in the regime of small couplings and light mediators where all other probes become inefficient. In the latter regime these scenarios behave as familiar $3+1$ models in all channels except for solar data, where a Solar Dark MSW effect takes place. Solar Dark MSW is characterized by modifications of the most energetic $^8$B and CNO neutrinos, whereas the other fluxes remain largely unaffected., Comment: 19 pages, 7 figures

We investigate the detection prospects of a non-standard dark sector in the context of boosted dark matter. We consider a scenario where two stable particles have a large mass difference and the heavier particle accounts for most of dark matter in our current universe. The heavier candidate is assumed to have no interaction with the standard model particles at tree-level, hence evading existing constraints. Although subdominant, the lighter dark matter particles are efficiently produced via pair-annihilation of the heavier ones in the center of the Galaxy or the Sun. The large Lorentz boost enables detection of the non-minimal dark sector in large volume terrestrial experiments via exchange of a light dark photon with electrons or nuclei. Various experiments designed for neutrino physics and proton decay are examined in detail, including Super-K and Hyper-K. In this study, we focus on the sensitivity of the far detector at the Deep Underground Neutrino Experiment for boosted dark matter produced in the center of the Sun, and compare our findings with recent results for boosted dark matter produced in the galactic center., 11 Pages, 5 Figures

DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary goal will be to explore the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass-range, until neutrino interactions with the target become an irreducible background. The prompt scintillation light and the charge signals induced by particle interactions in the xenon will be observed by VUV sensitive, ultra-low background photosensors. Besides its excellent sensitivity to WIMPs above a mass of 5 GeV/c2, such a detector with its large mass, low-energy threshold and ultra-low background level will also be sensitive to other rare interactions. It will search for solar axions, galactic axion-like particles and the neutrinoless double-beta decay of 136-Xe, as well as measure the low-energy solar neutrino flux with, 36 pages, 11 figures

The next generation of dark matter direct detection experiments will be sensitive to both coherent neutrino-nucleus and neutrino-electron scattering. This will enable them to explore aspects of solar physics, perform the lowest energy measurement of the weak angle to date, and probe contributions from new theories with light mediators. In this article, we compute the projected nuclear and electron recoil rates expected in several dark matter direct detection experiments due to solar neutrinos, and use these estimates to quantify errors on future measurements of the neutrino fluxes, weak mixing angle and solar observables, as well as to constrain new physics in the neutrino sector. Our analysis shows that the combined rates of solar neutrino events in second generation experiments (SuperCDMS and LZ) can yield a measurement of the $pp$ flux to 2.5% accuracy via electron recoil, and slightly improve the $^8$B flux determination. Assuming a low-mass argon phase, projected tonne-scale experiments like DARWIN can reduce the uncertainty on both the $pp$ and boron-8 neutrino fluxes to below 1%. Finally, we use current results from LUX, SuperCDMS and CDMSlite to set bounds on new interactions between neutrinos and electrons or nuclei, and show that future direct detection experiments can be used to set complementary constraints on the parameter space associated with light mediators., 15 pages. v3: corrected typos in Table IV and mistake in LUX constraints in Fig. 6

The recent observation of very high energy cosmic neutrinos by IceCube heralds the beginning of neutrino astronomy. At these energies, the dominant background to the astrophysical signal is the flux of `prompt' neutrinos, arising from the decay of charmed mesons produced by cosmic ray collisions in the atmosphere. In this work we provide predictions for the prompt atmospheric neutrino flux in the framework of perturbative QCD, using state-of-the-art Monte Carlo event generators. Our calculation includes the constraints set by charm production measurements from the LHCb experiment at 7 TeV, and has been recently validated with the corresponding 13 TeV data. Our results for the prompt flux are a factor of about 2 below the previous benchmark calculation, in general agreement with two other recent estimates, and with an improved estimate of the uncertainty. This alleviates the existing tension between the theoretical prediction and IceCube limits, and suggests that a direct direction of the prompt flux is imminent., Comment: 20 pages, 10 figures; corrected conventional flux in Fig. 6, to appear in JHEP. The PrompNuFlux code is available from http://promptnuflux.hepforge.org/

Precision measurements of solar neutrinos emitted by specific nuclear reaction chains in the Sun are of great interest for developing an improved understanding of star formation and evolution. Given the expected neutrino fluxes and known detection reactions, such measurements require detectors capable of collecting neutrino-electron scattering data in exposures on the order of 1 ktonne yr, with good energy resolution and extremely low background. Two-phase liquid argon time projection chambers (LAr TPCs) are under development for direct Dark Matter WIMP searches, which possess very large sensitive mass, high scintillation light yield, good energy resolution, and good spatial resolution in all three cartesian directions. While enabling Dark Matter searches with sensitivity extending to the "neutrino floor" (given by the rate of nuclear recoil events from solar neutrino coherent scattering), such detectors could also enable precision measurements of solar neutrino fluxes using the neutrino-electron elastic scattering events. Modeling results are presented for the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). The results show that such a detector could measure the CNO neutrino rate with ~15% precision, and significantly improve the precision of the 7Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector., Comment: 21 pages, 7 figures, 6 tables

We study the sensitivity of large-scale xenon detectors to low-energy solar neutrinos, to coherent neutrino-nucleus scattering and to neutrinoless double beta decay. As a concrete example, we consider the xenon part of the proposed DARWIN (Dark Matter WIMP Search with Noble Liquids) experiment. We perform detailed Monte Carlo simulations of the expected backgrounds, considering realistic energy resolutions and thresholds in the detector. In a low-energy window of 2-30 keV, where the sensitivity to solar pp and $^7$Be-neutrinos is highest, an integrated pp-neutrino rate of 5900 events can be reached in a fiducial mass of 14 tons of natural xenon, after 5 years of data. The pp-neutrino flux could thus be measured with a statistical uncertainty around 1%, reaching the precision of solar model predictions. These low-energy solar neutrinos will be the limiting background to the dark matter search channel for WIMP-nucleon cross sections below $\sim$2$\times$10$^{-48}$ cm$^2$ and WIMP masses around 50 GeV$\cdot$c$^{-2}$, for an assumed 99.5% rejection of electronic recoils due to elastic neutrino-electron scatters. Nuclear recoils from coherent scattering of solar neutrinos will limit the sensitivity to WIMP masses below $\sim$6 GeV$\cdot$c$^{-2}$ to cross sections above $\sim$4$\times$10$^{-45}$cm$^2$. DARWIN could reach a competitive half-life sensitivity of 5.6$\times$10$^{26}$ y to the neutrinoless double beta decay of $^{136}$Xe after 5 years of data, using 6 tons of natural xenon in the central detector region., Comment: 17 pages, 4 figures

Agradecimentos: A. E. thanks ICTP for hospitality, where this work initiated and partially done. A. E. acknowledges financial support by the funding grant 2009/17924-5, from Sao Paulo Research Foundation (FAPESP) Abstract: We study oscillations of the high energy atmospheric neutrinos in the Earth into sterile neutrinos with the eV-scale mass. The MSW resonance and parametric enhancement of the (nu) over bar (mu) -> (nu) over bar (s) oscillations lead to distortion of the zenith angle distribution of the muon-track events which can be observed by IceCube. Due to matter effect, the IceCube signal depends not only on the mixing element U-mu 4 relevant for LSND and MiniBooNE but also on U-tau 4 and the CP-violating phase delta(24). We show that the case with U-tau 4 = delta(24) = 0 leads to the weakest IceCube signal and therefore should be used to bound U-mu 4. We compute the zenith angle distributions of the nu(mu)-events for different energy intervals in the range (0.1 - 10) TeV and find that inclusion of the energy information (binning in energy) improves the sensitivity to nu(s) drastically. We estimate that with already collected (during 3 - 4 years) IceCube statistics the bound vertical bar U-mu 4 vertical bar(2) < 0.01 (99% C.L.) can be established and the mixing required by LSND and MiniBooNE can be excluded at (4-6)sigma confidence level FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: The authors thank CENAPAD and CCJDR for computing facilities. A. E. thanks FAPESP for financial support Abstract: We consider effects of the Non-Standard Interactions (NSI) on oscillations of the high energy atmospheric neutrinos. The v(mu)-oscillograms are constructed and their dependence on the NSI strength parameters epsilon(alpha beta) studied. We computed the zenith angle distributions of the v(mu)-events in the presence of NSI in different energy regions. The distributions are confronted with the IceCube-79 (high energy sample) and the DeepCore (low energy sample) data and constraints on the strength parameters vertical bar epsilon(mu T)vertical bar less than or similar to 6 x 10(-3) and vertical bar epsilon mu mu - epsilon tau tau vertical bar x 10(-2) (90% C.L.) have been obtained. Future measurements of the zenith angle distributions by DeepCore in several energy bins will allow to improve the bounds by factor 2-3. We discuss the signatures of NSI in the zenith angle and energy distributions of events which allow to discriminate them from the effects of sterile neutrinos FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

We develop a formalism for constructing the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix and neutrino masses using an expansion that originates when a sequence of heavy right handed neutrinos are integrated out, assuming a seesaw mechanism for the origin of neutrino masses. The expansion establishes relationships between the structure of the PMNS matrix and the mass differences of neutrinos, and allows symmetry implications for measured deviations from tri-bimaximal form to be studied systematically. Our approach does not depend on choosing the rotation between the weak and mass eigenstates of the charged lepton fields to be diagonal. We comment on using this expansion to examine the symmetry implications of the recent results from the Daya-Bay collaboration reporting the discovery of a non zero value for theta_{13}, indicating a deviation from tri-bimaximal form, with a significance of 5.2 sigma., 16 pp, 1 figure v2: Jhep version, more exposition/description,results unchanged

Agradecimentos: The work of F. H. is supported in part by the National Science Foundation under Grant No. OPP-0236449, by the DOE under grant DE-FG02-95ER40896 and in part by the University of Wisconsin Alumni Research Foundation. O. L. G. P. thanks the ICTP, FAPESP, CAPES and Fulbright commission for financial support, the C.N. Yang Institute at Stony Brook University and Arizona State University for the hospitality were this work was partially developed. A. E. thanks FAPESP and World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, for financial support. The authors thank CENAPAD and CCJDR for computing facilities Abstract: We demonstrate that atmospheric neutrino data accumulated with the AMANDA and the partially deployed IceCube experiments constrain the allowed parameter space for a hypothesized fourth sterile neutrino beyond the reach of a combined analysis of all other experiments, for Delta m(41)(2) less than or similar to 1 eV(2). Although the IceCube data wins the statistics in the analysis, the advantage of a combined analysis of AMANDA and IceCube data is the partial remedy of yet unknown instrumental systematic uncertainties. We also illustrate the sensitivity of the completed IceCube detector, that is now taking data, to the parameter space of 3+1 model FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Aberto

Journal of High Energy Physics 2011.5 (2011): 075 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA), We quantify our current knowledge of the size and flavor structure of the matter effects in the evolution of atmospheric and long-baseline neutrinos based solely on the analysis of the corresponding neutrino data. To this aim we generalize the matter potential of the Standard Model by rescaling its strength, rotating it away from the ee sector, and rephasing it with respect to the vacuum term. This phenomenological parametrization can be easily translated in terms of non-standard neutrino interactions in matter. We show that in the most general case, the strength of the potential cannot be determined solely by atmospheric and long-baseline data. However its flavor composition is very much constrained and the present determination of the neutrino masses and mixing is robust under its presence. We also present an update of the constraints arising from this analysis in the particular case in which no potential is present in the eμ and eτ sectors. Finally we quantify to what degree in this scenario it is possible to alleviate the tension between the oscillation results for neutrinos and antineutrinos in the MINOS experiment and show the relevance of the high energy part of the spectrum measured at MINOS, This work is supported by Spanish MICINN grants 2007-66665-C02-01, FPA-2009-08958, FPA-2009-09017 and consolider-ingenio 2010 grant CSD-2008-0037, by CUR Generalitat de Catalunya grant 2009SGR502, by Comunidad Autónoma de Madrid through the HEPHACOS project S2009/ESP-1473, by USA-NSF grant PHY-0969739 and by EU grant EURONU

19 pages, 9 figures., We present an up-to-date global analysis of solar, atmospheric, reactor and accelerator neutrino data in the framework of three-neutrino oscillations. We discuss in detail the statistical significance of the observed "hint" of non-zero theta13 in the solar sector at the light of the latest experimental advances, such as the Borexino spectral data, the lower value of Gallium rate recently measured in SAGE, and the low energy threshold analysis of the combined SNO phase I and phase II. We also study the robustness of the results under changes of the inputs such as the choice of solar model fluxes and a possible modification of the Gallium capture cross-section as proposed by SAGE. In the atmospheric sector we focus on the latest results for nu_e appearance from MINOS, and we discuss their impact on the determination of theta13. Finally, we combine all the data into a global analysis and determine the presently allowed ranges of masses and mixing., This work is supported by Spanish MICINN grants 2007-66665-C02-01, FPA-2009-08958 and FPA-2009-09017 and consolider-ingenio 2010 grant CSD-2008-0037, by CUR Gener- alitat de Catalunya grant 2009SGR502, by Comunidad Autonoma de Madrid through the HEPHACOS project P-ESP-00346, by USA-NSF grant PHY-0653342 and by EU grant EURONU.

11 pages, 11 figures.-- ISI article identifier:000267776100008 .-- ArXiv pre-print avaible at: http://arxiv.org/abs/0904.0796, Neutrino radiography may provide an alternative tool to study the very deep structures of the Earth. Though these measurements are unable to resolve the fine density layer features, nevertheless the information which can be obtained are independent and complementary to the more conventional seismic studies. The aim of this paper is to assess how well the core and mantle averaged densities can be reconstructed through atmospheric neutrino radiography. We find that about a 2% sensitivity for the mantle and 5% for the core could be achieved for a ten year data taking at an underwater km(3) Neutrino Telescope. This result does not take into account systematics related to the details of the experimental apparatus., This work is supported by the Istituto Nazionale di Fisica Nucleare I.S. Fa51, the PRIN 2006 “Fisica Astroparticellare: Neutrini ed Universo Primordiale” of the Italian Minis- tero dell’Istruzione, Universit`a e Ricerca, the Spanish MICINN (grants SAB2006-0171 and FPA2008-00319), by a MICINN-INFN agreement, and by the European Union under the ILIAS project (Contract No. RII3-CT-2004-506222).

54 pages, 14 figures, 1 table.-- Pre-print archive., We study the potential of a Neutrino Factory in constraining the parameter space of a scheme with one sterile neutrino separated from three active ones by an O(1) eV2 mass-squared difference. We present approximated analytic expressions for the oscillation probabilities, showing that the greatest sensitivity to sterile neutrinos at a Neutrino Factory can be achieved using the νμ → νμ and the νμ → ντ oscillations. We have studied two setups: a Neutrino Factory with 50 GeV (20 GeV) stored muons, with two detectors of the Hybrid-MIND type (a magnetized ECC next to a magnetized iron calorimeter), located at L = 3000, 7500 km (L = 4000, 7500 km) from the source. Four channels have been used: νe → νμ,ντ; νμ → νμ,ντ. The relevant backgrounds, efficiencies and systematic errors have been taken into account, and we have discussed dependence of the sensitivities on the systematic errors. We have found that the 50 GeV (20 GeV) setup can constrain sin2 2θ(4fam)13 ≤ 7 × 10−5 (2 × 10−4); θ34 ≤ 12° (14°); and θ24 ≤ 7.5° (8°). Our results hold for any value of Δm2SBLgtrsim0.1 eV2. Eventually we have shown that, if a positive signal is found, the proposed setup is able to measure simultaneously θ34 and δ3 with a precision of few degrees and few tens of degrees, respectively, solving the so-called "intrinsic" and "sign degeneracies". Combination of νμ disappearance and of the νμ → ντ channel, that will be called "the discovery channel'', at the two baselines is able to measure at 99% CL a new CP-violating phase δ3 for sin2 2θ34 ≥ 0.06., We acknowledge H. Minakata for useful comments, M. Maltoni and P. Migliozzi for useful discussions, and P. Lipari and M. Lusignoli for discussions. The work has been partially supported by the JSPS-CSIC Bilateral Joint Projects (Japan- Spain), a Grant-in-Aid for Scientific Research of the Ministry of Education, Science and Culture of Japan,#19340062. K.F. thanks the support by the MEXT program ”Support Program for Improving Graduate School Education”; J. L.-P. acknowledges partial financial support by the Ministry of Science and Innovation of Spain (MICIINN) through an FPU grant, ref. AP2005-1185; A.D. acknowledges partial financial support by the Istituto Nazionale di Fisica Nucleare (INFN) through the Iniziativa Specifica RM21 for foreign guests; and by the MICINN through the research project FPA2006-05423 and through the INFN-MICINN-08 Bilateral Agreement (Italy-Spain) ”Flavour as a window for new physics”; D.M. acknowledges partial financial support by Ministry of University and of Scientific Research of Italy, through the 2007-08 COFIN program. A.D. and J.L.-P. acknowledge also financial support from the Comunidad Aut´onoma de Madrid through the project P-ESP-00346. Eventually, A.D., J.L.-P. and D.M. acknowledge the financial support of the European Community under the European Commission Framework Programme 7 Design Study: EUROnu, Project Number 212372; and under the Framework Programme 6 BENE-CARE networking activity MRTN-CT-2004-506395. The EC is not liable for any use that may be made of the information contained herein. A.D. and J.L.-P. thank the Physics Department of the Universit`a di Roma ”La Sapienza”, where this work has been completed.

Agradecimentos: We are grateful to J Garriga, J A Grifols and S Mohanty for useful discussions. This work is supported by National Science Foundation grant PHY-0354776, by Spanish grants FPA2004-00996 and FPA2005-05904, by Catalan DURSI grant 2005SGR00916, by Fundaação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and by Conselho Nacional de Ciência e Tecnologia (CNPq) Abstract: In this work we study the phenomenological consequences of the existence of long-range forces coupled to lepton flavour numbers in solar neutrino oscillations. We study electronic forces mediated by scalar, vector or tensor neutral bosons and analyse their effect on the propagation of solar neutrinos as a function of the force strength and range. Under the assumption of one mass scale dominance, we perform a global analysis of solar and KamLAND neutrino data which depends on the two standard oscillation parameters, Delta m(21)(2) and tan(2)theta(12), the force coupling constant, its range and, for the case of scalar-mediated interactions, on the neutrino mass scale as well. We find that, generically, the inclusion of the new interaction does not lead to a very statistically significant improvement on the description of the data in the most favored MSW LMA ( or LMA-I) region. It does, however, substantially improve the fit in the high-Delta m(2) LMA ( or LMA-II) region which can be allowed for vector and scalar lepto-forces ( in this last case if neutrinos are very hierarchical) at 2.5 sigma. Conversely, the analysis allows us to place stringent constraints on the strength versus range of the leptonic interaction FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

We discuss the phenomenology of damping signatures in the neutrino oscillation probabilities, where either the oscillating terms or the probabilities can be damped. This approach is a possibility for tests of non-oscillation effects in future neutrino oscillation experiments, where we mainly focus on reactor and long-baseline experiments. We extensively motivate different damping signatures due to small corrections by neutrino decoherence, neutrino decay, oscillations into sterile neutrinos, or other mechanisms, and classify these signatures according to their energy (spectral) dependencies. We demonstrate, at the example of short baseline reactor experiments, that damping can severely alter the interpretation of results, e.g., it could fake a value of $\sin(2\theta_{13})$ smaller than the one provided by Nature. In addition, we demonstrate how a neutrino factory could constrain different damping models with emphasis on how these different models could be distinguished, i.e., how easily the actual non-oscillation effects could be identified. We find that the damping models cluster in different categories, which can be much better distinguished from each other than models within the same cluster., Comment: 33 pages, 5 figures, LaTeX. Final version published in JHEP