Super-kamiokande atmospheric neutrino analysis of matter-dependent neutrino oscillation models

Abstract

Current data finds that the atmospheric neutrino anomaly is best explained with numu - nutau neutrino oscillations. However, there is motivation for the Mass Varying Neutrino (MaVaN) model as an explanation for the presence of dark energy and the results of LSND. A possible consequence of said model is a bias in the neutrino mass from the electron density rho e of the matter a neutrino passes through. Using the data from Super-Kamiokande-I, numu - nutau oscillation models whose mass differences are proportional to (rhoe) n are applied to the Monte Carlo predictions for several different n values. A constant mixing angle in all densities is assumed. For each density dependence hypothesis, two sets of models are applied, which do not or do account for the air pathlength. In all of the specific models tested, the density dependent oscillations are disfavored at greater than a 3sigma level compared with 2-flavor oscillations with a fixed mass in all environments. In addition, a separate analysis which assumes maximal mixing finds that a best-fit 2-flavor oscillation of varying density dependence is consistent with no dependence on electron density within 1sigma.