Updated constraints on sterile neutrino mixing in the OPERA experiment using a new $\nu_e$ identification method

TL;DR

This paper introduces a new $ u_e$ identification method for the OPERA experiment, significantly enhancing low-energy neutrino detection efficiency and tightening constraints on sterile neutrino mixing parameters.

Contribution

The paper presents a novel $ u_e$ identification technique that improves detection efficiency and sensitivity in the OPERA experiment for sterile neutrino searches.

Findings

25-70% increase in $ u_e$ detection efficiency at low energies

Additional $ u_e$ candidate identified, improving sensitivity

Upper limit on $ ext{sin}^2 2 heta_{ ext{μe}}$ constrained to 0.016

Abstract

This paper describes a new $\nu_e$ identification method specifically designed to improve the low-energy ($< 30\,\mathrm{GeV}$) $\nu_e$ identification efficiency attained by enlarging the emulsion film scanning volume with the next generation emulsion readout system. A relative increase of 25-70% in the $\nu_e$ low-energy region is expected, leading to improvements in the OPERA sensitivity to neutrino oscillations in the framework of the 3 + 1 model. The method is applied to a subset of data where the detection efficiency increase is expected to be more relevant, and one additional $\nu_e$ candidate is found. The analysis combined with the $\nu_\tau$ appearance results improves the upper limit on $\sin^2 2\theta_{\mu e}$ to 0.016 at 90% C.L. in the MiniBooNE allowed region $\Delta m^2_{41} \sim 0.3\,\mathrm{eV}^2$.