Revised neutrino-gallium cross section and prospects of BEST in resolving the Gallium anomaly

TL;DR

This paper revises the neutrino-gallium cross section using recent data, refines the Gallium anomaly parameters, and demonstrates that the BEST experiment can potentially discover sterile neutrinos responsible for the anomaly with high confidence.

Contribution

It provides a updated cross section calculation, refines the Gallium anomaly parameters, and assesses the sensitivity of the BEST experiment to sterile neutrinos using Bayesian analysis.

Findings

Revised neutrino-gallium cross section based on recent measurements.

Refined parameters of the Gallium anomaly.

Projected 5σ discovery potential of BEST for sterile neutrinos.

Abstract

O(1) eV sterile neutrino can be responsible for a number of anomalous results of neutrino oscillation experiments. This hypothesis may be tested at short base-line neutrino oscillation experiments, several of which are either ongoing or under construction. Here we concentrate on the so-called Gallium anomaly, found by SAGE and GALLEX experiments, and its foreseeable future tests with BEST experiment at Baksan Neutrino Observatory. We start with a revision of the neutrino-gallium cross section, that is performed by utilizing the recent measurements of the nuclear final state spectra. We accordingly correct the parameters of Gallium anomaly and refine the BEST prospects in testing it and searching for sterile neutrinos. We further evolve the previously proposed idea to investigate the anomaly with Zn-65 artificial neutrino source as a next option available at BEST, and estimate its sensitivity to the sterile neutrino model parameters following the Bayesian approach. We show that after the two stages of operation BEST will make 5$\sigma$-discovery of the sterile neutrinos, if they are behind the Gallium anomaly.