Status of 3+1 Neutrino Mixing

TL;DR

This paper updates the analysis of short-baseline neutrino oscillation data within the 3+1 mixing framework, addressing recent experimental results and tensions between appearance and disappearance data, and exploring implications for sterile neutrino parameters.

Contribution

It provides an updated global fit of 3+1 neutrino mixing parameters incorporating recent MiniBooNE and MINOS data, highlighting tensions and potential sterile neutrino mass regions.

Findings

Best-fit Delta m^2_{41} around 5.6 eV^2

Regions within 1 sigma at Delta m^2_{41} about 1.6, 1.2, 0.91 eV^2

Gallium anomaly favors Delta m^2_{41} > 1 eV^2

Abstract

We present an update of our analysis of short-baseline neutrino oscillation data in the framework of 3+1 neutrino mixing taking into account the recent update of MiniBooNE antineutrino data and the recent results of the MINOS search for nu_mu disappearance into sterile neutrinos (the more complicated 3+2 neutrino mixing is not needed since the CP-violating difference between MiniBooNE neutrino and antineutrino data has diminished). The results of our fits of short-baseline neutrino oscillation data including the MiniBooNE low-energy anomaly (now present both in the neutrino and antineutrino data) leads to a strong tension between appearance and disappearance data. Hence, it seems likely that the low-energy anomaly is not due to nu_mu -> nu_e transitions. Excluding the MiniBooNE low-energy anomaly, appearance and disappearance data are marginally compatible. The global analysis has the best-fit point at Delta m^2_{41} about 5.6 eV^2, which is rather large in comparison with cosmological bounds, but there are three regions within 1 sigma at Delta m^2_{41} about 1.6, 1.2, 0.91 eV^2. We also show that the data on the Gallium neutrino anomaly favor values of Delta m^2_{41} larger than about 1 eV^2.