The Observation of Up-going Charged Particles Produced by High Energy Muons in Underground Detectors

TL;DR

This study investigates up-going charged particles produced by high-energy muons in underground detectors, analyzing their characteristics and implications as a background in neutrino flux measurements.

Contribution

It provides the first detailed analysis of up-going particles from muon interactions in underground detectors, highlighting their potential as background in neutrino experiments.

Findings

243 up-going events observed from 12.2 million muons

Range and emission angle distributions characterized

Implications for neutrino flux measurements discussed

Abstract

An experimental study of the production of up-going charged particles in inelastic interactions of down-going underground muons is reported, using data obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of 12.2 10^6 single muons, corresponding to a detector livetime of 1.55 y, 243 events are observed having an up-going particle associated with a down-going muon. These events are analysed to determine the range and emission angle distributions of the up-going particle, corrected for detection and reconstruction efficiency. Measurements of the muon neutrino flux by underground detectors are often based on the observation of through-going and stopping muons produced in $\nu_\mu$ interactions in the rock below the detector. Up-going particles produced by an undetected down-going muon are a potential background source in these measurements. The implications of this background for neutrino studies using MACRO are discussed.