We consider the ν µ → ν τ appearance channel in the future Deep Underground Neutrino Experiment (DUNE) which offers a good statistics of the ν τ sample. In order to measure its impact on constraining the oscillation parameters, we consider several assumptions on the efficiency for ν τ charged-current signal events (with subsequent τ → e decay) and the related backgrounds and study the effects of various systematic uncertainties. Two different neutrino fluxes have been considered, namely a CP-violation optimized flux and a ν τ optimized flux.Our results show that the addition of the ν µ → ν τ appearance channel does not reduce the current uncertainties on the standard 3-ν oscillation parameters while it can improve in a significant way the sensitivity to the Non-Standard Interaction parameter | µτ | and to the new mixing angle θ 34 of a sterile neutrino model of the 3 + 1 type.

The hypothesis of the decay of neutrino mass eigenstates leads to a substantial modification of the appearance and disappearance probabilities of flavor eigenstates. We investigate the impact on the standard oscillation scenario caused by the decay of the heaviest mass eigenstate ν 3 (with a mass m 3 and a mean life τ 3) to a sterile state in deep underground neutrino experiment. We find that the lower bound of 5.1 × 10−11 s eV−1 at 90% confidence level on the decay parameter τ 3/m 3 can be set if the neutral current data are included in the analysis, thus providing the best long-baseline expected limit so far. We also show that the ν τ appearance channel would give only a negligible contribution to the decay parameter constraints. Our numerical results are corroborated by analytical formulae for the appearance and disappearance probabilities in vacuum (which is a useful approximation for the study of the invisible decay model) that we have developed up to the second order in the solar mass splitting and to all orders in the decay factor t/τ 3.

No abstract

Our knowledge on the active 3ν mixing angles (θ12, θ13, and θ23) and the CP phase δCP is becoming accurate day-by-day enabling us to test the unitarity of the leptonic mixing matrix with utmost precision. Future high-precision long-baseline experiments are going to play an important role in this direction. In this work, we study the impact of possible non-unitary neutrino mixing (NUNM) in the context of next-generation long-baseline experiments DUNE and T2HKK/JD+KD having one detector in Japan (T2HK/JD) and a second detector in Korea (KD). We estimate the sensitivities of these setups to place direct, model-independent, and competitive constraints on various NUNM parameters. We demonstrate the possible correlations between the NUNM parameters, θ23, and δCP. Our numerical results obtained using only far detector data and supported by simple approximate analytical expressions of the oscillation probabilities in matter, reveal that JD+KD has better sensitivities for |α21| and α22 as compared to DUNE, due to its larger statistics in the appearance channel and less systematic uncertainties in the disappearance channel, respectively. For |α31|, |α32|, and α33, DUNE gives better constraints as compared to JD+KD, due to its larger matter effect and wider neutrino energy spectrum. For α11, both DUNE and JD+KD give similar bounds. We also show how much the bounds on the NUNM parameters can be improved by combining the prospective data from DUNE and JD+KD setups. We find that due to zero-distance effects, the near detectors alone can also constrain α11, |α21|, and α22 in both these setups. Finally, we observe that the ντ appearance sample in DUNE can improve the constraints on |α32| and α33.

We check the capability of the DUNE neutrino experiment to detect new sources of leptonic CP violation beside the single phase expected in the Standard Model. We illustrate our strategy based on the measurement of CP asymmetries in the case that new physics will show up as nonstandard neutrino interactions and sterile neutrino states and show that the most promising one, once the experimental errors are taken into account in both scenarios, is the one related to the νμ→νe transition.