Combined analysis of short-baseline neutrino experiments in the(3+1)and(3+2)sterile neutrino oscillation hypotheses

Abstract

We investigate adding two sterile neutrinos to resolve the apparent tension existing between short-baseline neutrino oscillation results and CPT-conserving, four-neutrino oscillation models. For both $(3+1)$ and $(3+2)$ models, the level of statistical compatibility between the combined dataset from the null short-baseline experiments Bugey, CHOOZ, CCFR84, CDHS, KARMEN, and NOMAD, on the one hand; and the LSND dataset, on the other, is computed. A combined analysis of all seven short-baseline experiments, including LSND, is also performed, to obtain the favored regions in neutrino mass and mixing parameter space for both models. Finally, four statistical tests to compare the $(3+1)$ and the $(3+2)$ hypotheses are discussed. All tests show that $(3+2)$ models fit the existing short-baseline data significantly better than $(3+1)$ models.