Inaccessibility regions for the sterile neutrino searches at the long baseline experiments

Abstract

We provide a novel approach based on χ2 analysis that investigates regions in the neutrino parameter space where long baseline experiments cannot discriminate between the (3+1)ν oscillation scheme and the standard 3ν oscillation scheme. We call such region of parameter space “the inaccessible region”. The inaccessible area of parameter space is so named because the minimal value of χ2 remains almost unaltered even after inserting the sterile neutrino in the description of the neutrino oscillation data. Such inaccessible zones are discovered for the three long-baseline experiments (T2K, NOva and DUNE). Finally, we find the region of the sterile neutrino parameter space that remains inaccessible even after combining all three experiments. If sterile neutrinos exist in nature but their mixing parameters are in this range, these long-baseline experiments cannot prove their existence. The significance of our finding stems from the likelihood of sterile neutrinos existing in the accessible zone, which may be tested in these experiments in near future.