Effects of New Physics on Neutrino Interactions

Abstract

Effects of New Physics on Neutrino Interactions We explore the effects of neutrino interactions due to new physics with the standard Lorentz structure, but with the nonstandard flavor structure in the reactor electron- antineutrino disappearance short- and medium-baseline oscillation and in the very- short-baseline scattering experiments. In both types of experiments, we explore the nonstandard interactions of neutrinos produced in the charged current neutron beta decays and, later on, when detected through inverse beta decay and through purely leptonic elastic scattering processes. In oscillation experiments, there is degeneracy between oscillations and the new interactions, whereas the scattering experiments are free from the degeneracy because of their baseline short enough to ignore the standard oscillation phenomenon. In oscillation experiments, we draw on the short-baseline Daya Bay and its future upgrade JUNO for the spectral event rate and the statistical analyses and in the scattering experiments TEXONO and its future upgrade version with improved statistical sensitivities for confidence level boundary regions of the nonstandard neutrino interaction parameters. In the oscillation experiments, we find that the average spectrum of observed events at a baseline of 50 km, in the middle of the currently favored region, provides improvement in sensitivity to new physics if combined with improved precision of input mixing parameters in independent experiments, despite of the ambiguity due to the degeneracy between new physics and oscillations in medium-baseline data. Moreover, the nonstandard interactions can enhance or suppress the sensitivity of experiments to the mass hierarchy, depending on the combination of nonstandard and the standard CP-violating phases. In the scattering experiments, we confirm that the current data of TEXONO experiment allows for new physics constraints at the detector of the same order as those currently published. The new physics phase effects are at the 5% level, noticeable in the 90% contour plots but not significantly affecting the conclusions. Based on the projected statistical sensitivities with an upgraded version of TEXONO experiment, we estimate sensitivity of new physics at both source and detector. We find that bounds on source nonstandard interaction parameters improve by an order of magnitude, but do not reach parameter space beyond current limits. On the other hand, the detector new physics sensitivity would push current limits by maximum of an order of magnitude.