Measurement of the underground atmospheric muon charge ratio using the MINOS Near Detector

TL;DR

This study measures the atmospheric muon charge ratio at a shallow underground depth using the MINOS Near Detector, providing data consistent with previous measurements and insights into muon production mechanisms.

Contribution

First measurement of muon charge ratio at 225 mwe depth using the MINOS Near Detector, comparing results with the deeper MINOS Far Detector to study depth dependence.

Findings

Charge ratio measured as 1.266±0.001(stat.)±0.015(syst.)

Charge ratio is lower than at the deeper detector by 0.108±0.019

Increase in charge ratio with depth suggests more muons from kaon decay

Abstract

The magnetized MINOS Near Detector, at a depth of 225 meters of water equivalent (mwe), is used to measure the atmospheric muon charge ratio. The ratio of observed positive to negative atmospheric muon rates, using 301 days of data, is measured to be 1.266+/-0.001(stat.)+0.015/-0.014(syst.). This measurement is consistent with previous results from other shallow underground detectors, and is 0.108+/-0.019(stat. + syst.) lower than the measurement at the functionally identical MINOS Far Detector at a depth of 2070 mwe. This increase in charge ratio as a function of depth is consistent with an increase in the fraction of muons arising from kaon decay for increasing muon surface energies.