3+1 and 3+2 Sterile Neutrino Fits

TL;DR

This paper analyzes short-baseline neutrino oscillation data within 3+1 and 3+2 sterile neutrino models, highlighting their fits, tensions, and potential for future experimental testing, with 3+2 allowing CP violation explanations.

Contribution

It provides the first comprehensive comparison of 3+1 and 3+2 sterile neutrino models with detailed fits to short-baseline data, including CP violation effects.

Findings

3+1 model is simple but has data tension.

3+2 model reduces tension with an extra sterile neutrino.

CP violation in 3+2 can explain MiniBooNE results.

Abstract

We present the results of fits of short-baseline neutrino oscillation data in 3+1 and 3+2 neutrino mixing schemes. In spite of the presence of a tension in the interpretation of the data, 3+1 neutrino mixing is attractive for its simplicity and for the natural correspondence of one new entity (a sterile neutrino) with a new effect (short-baseline oscillations). The allowed regions in the oscillation parameter space can be tested in near-future experiments. In the framework of 3+2 neutrino mixing there is less tension in the interpretation of the data, at the price of introducing a second sterile neutrino. Moreover, the improvement of the parameter goodness of fit is mainly a statistical effect due to an increase of the number of parameters. The CP violation in short-baseline experiments allowed in 3+2 neutrino mixing can explain the positive antinu_mu -> antinu_e signal and the negative nu_mu -> nu_e measurement in the MiniBooNE experiment. For the CP-violating phase we obtained two minima of the marginal chi^2 close to the two values where CP-violation is maximal.