Neutrino interactions at COMET

TL;DR

This paper evaluates the expected positron event rates from neutrino interactions in the COMET experiment, which is designed to search for rare muon-to-electron conversion processes indicating new physics beyond the Standard Model.

Contribution

It provides the first detailed calculation of positron event rates from neutrino interactions in the COMET experimental setup, highlighting an additional background consideration.

Findings

Approximately 7±1 positron events per 10^18 stopped muons are expected from neutrino interactions.

The study emphasizes the significance of neutrino-induced backgrounds in the sensitivity of COMET and PRISM experiments.

Results inform background modeling for future searches of charged lepton flavor violation.

Abstract

The experimental search for coherent neutrinoless conversion of muon to electron in the presence of a nucleus, aims to probe the possibility of charged lepton flavour violation. The COMET experiment at J-PARC is one such setup offering unprecedented statistical reach, with single event sensitivities down to $\mathcal{O}$ ($\mathrm{10^{-17}}$). Its successor experiment - PRISM, planned as the final stage, is expected to take this bound further down by two orders of magnitude. The electrons from standard model decay of bound muons are considered the most formidable physics background to the detection of these conversion electrons. Keeping in view the high stopped muon statistics for COMET and PRISM, the rate of charged current interaction of decay neutrinos with nuclear protons is also non-negligible. In this work, we perform a calculation of the positron event rates expected due to interactions of electron antineutrinos with Al target protons in the COMET setup. About $\mathrm{7\pm1}$ such $\mathrm{e^{+}}$ events per $\mathrm{10^{18}}$stopped muons are expected.