Muon-induced background to proton decay in the $p \rightarrow K^{+}\nu$ decay channel with large underground liquid argon TPC detectors

TL;DR

This paper estimates the background noise from muons in large underground liquid argon detectors for proton decay, showing it is very low and manageable over long exposure times.

Contribution

It provides a detailed simulation-based estimate of muon-induced background rates for proton decay searches in large liquid argon TPCs.

Findings

Background rate estimated at < 0.0012 events/kt/year

Simulations performed with MUSIC and Geant4 frameworks

Background is negligible for long-term proton decay experiments

Abstract

Large liquid argon TPC detector programs such as LBNE and LAGUNA-LBNO will be able to make measurements of the proton lifetime which will outperform Cherenkov detectors in the proton decay channel $p \rightarrow K^{+}\nu$. At the large depths which are proposed for such experiments, a non-negligible source of isolated charged kaons may be produced in the showers of cosmogenic muons. We present an estimate of the cosmogenic muon background to proton decay in the $p \rightarrow K^{+}\nu$ channel. The simulation of muon transport to a depth of 4 km w.e, is performed in the MUSIC framework and the propagation of muons and secondary particles through to a cylindrical 20 kt LAr target is performed using Geant4. An exposure time of 100 years is considered, with a rate of $< 0.0012$ events/kt/year at 90$\%$ CL predicted from our simulations.