Updated constraints on sterile neutrino mixing in the OPERA experiment using a new νe identification method. (24th January 2023) - ,
Abstract: This paper describes a new ν e identification method specifically designed to improve the low-energy ($\lt {30}\, {\rm GeV}$ ) ν 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 ν 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 ν e candidate is found. The analysis combined with the ντ appearance results improves the upper limit on sin 2 2θμ e to 0.016 at 90% C.L. in the MiniBooNE allowed region $\Delta m^2_{41} \sim {0.3}\, {\rm eV}^{2}$ .