Photon emission in neutral current interactions at the T2K experiment

TL;DR

This paper models single photon emission in neutral current interactions at T2K, revealing a higher event rate than previous simulations, which impacts background estimates for neutrino oscillation measurements.

Contribution

It introduces a microscopic model for photon emission that predicts a larger number of events than existing generators, refining background estimations for T2K.

Findings

Photon event count is twice that of NEUT generator.

Detailed energy and angular distribution comparisons.

Implications for neutrino oscillation background estimates.

Abstract

We have applied a microscopic model for single photon emission in neutral current interactions on nucleons and nuclei to determine the number and distributions of such events at the Super-Kamiokande detector, for the flux and beam exposure of the T2K experiment in neutrino mode. These reactions represent an irreducible background in electron-(anti)neutrino appearance measurements aimed at a precise measurement of mixing angle $\theta_{13}$ and the $CP$ violating phase. We have obtained a total number of photon events that is twice larger than the one from the NEUT event generator (version 5.1.4.2) used in the analysis of T2K data. Detailed comparisons of energy and angular distributions for the $\nu_\mu$ and $\bar\nu_\mu$ fluxes have also been performed.