Data from solar neutrino and KamLAND experiments have led to a discovery of nonzero neutrino masses. Here we investigate what these data can tell us about neutrino interactions with matter, including the poorly constrained flavor-changing νe − ντ interactions. We give examples of the interaction parameters that are excluded by the solar/KamLAND data and are beyond the reach of other experiments. We also demonstrate that flavor-changing interactions, at the allowed level, may profoundly modify the conversion probability for neutrinos of energy 6 MeV and the values of the mass parameter inferred from the data. The implications for future experiments are discussed.

We study the physics potential of the detection of the Cosmic Neutrino Background via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of ∆ ∼ 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m 1 m 2 m 3 = m ν 0.1 eV. These neutrinos are non-relativistic today; detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2m ν above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is ∆ 0.7 m ν . Interestingly, the total capture rate depends on the origin of the neutrino mass, being Γ D 4 and Γ M 8 events per year (for a 100 g tritium target) for unclustered Dirac and Majorana neutrinos, respectively. An enhancement of the rate of up to O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Turning to more exotic neutrino physics, PTOLEMY could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. The experiment would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.

We consider in details the effects of the 13-mixing (sin 2 θ 13 ) and of the type of mass hierarchy/ordering (sign[∆m 2 13 ]) on neutrino signals from the gravitational collapses of stars. The observables (characteristics of the energy spectra of ν e andν e events) sensitive to sin 2 θ 13 and sign[∆m 2 13 ] have been calculated. They include the ratio of average energies of the spectra, r E ≡ E / Ē , the ratio of widths of the energy distributions, r Γ ≡ Γ/Γ, the ratios of total numbers of ν e andν e events at low energies, S, and in the high energy tails, R tail . We construct and analyze scatter plots which show the predictions for the observables for different intervals of sin 2 θ 13 and signs of ∆m 2 13 , taking into account uncertainties in the original neutrino spectra, the star density profile, etc.. Regions in the space of observables r E , r Γ , S, R tail exist in which certain mass hierarchy and intervals of sin 2 θ 13 can be identified or discriminated. We elaborate on the method of the high energy tails in the spectra of events. The conditions are formulated for which sin 2 θ 13 can be (i) measured, (ii) restricted from below, (iii) restricted from above. We comment on the possibility to determine sin 2 θ 13 using the time dependence of the signals due to the propagation of the shock wave through the resonance layers of the star. We show that the appearance of the delayed Earth matter effect in one of the channels (ν e orν e ) in combination with the undelayed effect in the other channel will allow to identify the shock wave appeareance and determine the mass hierarchy.

Neutrino oscillation experiments provide a unique tool for probing neutrino-matter interactions, especially those involving the tau neutrino. We describe the sensitivity of the present atmospheric neutrino data to these interactions in the framework of a three-flavor analysis. Compared to the two-flavor nu_mu-nu_tau analyses, we find qualitatively new features, in particular, that large non-standard interactions, comparable in strength to those in the Standard Model, can be consistent with the data. The existence of such interactions could imply a smaller value of the neutrino mixing angle and larger value of the mass-squared splitting than in the case of standard interactions only. This and other effects of non-standard interactions may be tested in the next several years by MINOS, KamLAND and solar neutrino experiments.Comment: 5 pages, 2 figures; updated to match the journal version (Phys. Rev. D70, 111301(R) (2004)

The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21-26 June 2005) and NuFact06 (Ivine, CA, 24-30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.

In this work we study the the sensitivity of the T2HKK experiment to probe non-standard interaction in neutrino propagation. As this experiment will be statistically dominated due to its large detector volume and high beam-power, it is expected that the sensitivity will be affected by systematics. This motivates us to study the effect of systematics in probing the non-standard interaction. We also compare our results with the other future proposed experiments i.e., T2HK, HK and DUNE.

We perform a detailed study of the Earth matter effects on supernova neutrinos. The dependences of these effects on the properties of the original neutrino fluxes, on the trajectory of the neutrinos inside the Earth and on the oscillation parameters are described. We show that, for a large fraction (60 %) of the possible arrival times of the signal, the neutrino flux crosses a substantial amount of the matter of the Earth at least for one of the existing detectors. For oscillation parameters from the LMA solution of the solar neutrino problem the Earth matter effect consists in an oscillatory modulation of the $\barnue$ and/or $\nu_e$ energy spectra. The relative deviation with respect to the undistorted spectra can be as large as 20-30 % for E> 20 MeV and 70-100 % for E> 40 MeV. For parameters from the SMA and LOW solutions the effect is localized at low energies (E<10 MeV) and is not larger than 10 %. The Earth matter effects can be revealed (i) by the observation of oscillatory distortions of the energy spectra in a single experiment and (ii) by the comparison between the spectra at different detectors. For a supernova at distance D=10 Kpc, comparing the results of SuperKamiokande (SK), SNO and LVD experiments one can establish the effect at (2-3) \sigma level, whereas larger statistical significance ((4-5) \sigma) is obtained if two experiments of SK-size or larger are available. Studies of the Earth matter effect will select or confirm the solution of the solar neutrino problem, probe the mixing U_{e 3} and identify the hierarchy of the neutrino mass spectrum.Comment: LaTeX, 54 pages, 21 figures. Slight modifications in the discussion on the identification of Earth effects, minor changes in the figures and in the notation, typos corrected, references adde

We study matter effects on oscillations of high-energy neutrinos in the Universe. Substantial effect can be produced by scattering of the neutrinos from cosmological sources ($z\gta 1$) on the relic neutrino background, provided that the latter has large CP-asymmetry: $\eta\equiv (n_\nu-n_{\bar{\nu}})/n_\gamma\gta 1$, where $n_\nu$, $n_{\bar{\nu}}$ and $n_\gamma$ are the concentrations of neutrinos, antineutrinos and photons. We consider in details the dynamics of conversion in the expanding neutrino background. Applications are given to the diffuse fluxes of neutrinos from GRBs, AGN, and the decay of super-heavy relics. We find that the vacuum oscillation probability can be modified by $\sim (10-20)%$ and in extreme cases allowed by present bounds on $\eta$ the effect can reach $\sim 100%$. Signatures of matter effects would consist (i) for both active-active and active-sterile conversion, in a deviation of the numbers of events produced in a detector by neutrinos of different flavours, $N_{\alpha}~(\alpha=e,\mu,\tau)$, and of their ratios from the values given by vacuum oscillations; such deviations can reach $\sim 5-15%$, (ii) for active-sterile conversion, in a characteristic energy dependence of the ratios $N_{e}/N_{\mu},N_{e}/N_{\tau},N_{\mu}/N_{\tau}$. Searches for these matter effects will probe large CP and lepton asymmetries in the universe.Comment: 32 pages, RevTeX, 16 figures. Substantial changes in the treatment of conversion effects in the relic neutrino background and of active-active oscillations of high-energy neutrinos. Figures and references added; conclusions partially modifie