Measurement of the Charge Ratio of Atmospheric Muons with the CMS Detector

TL;DR

This study presents a highly precise measurement of the atmospheric muon charge ratio across a wide momentum range using the CMS detector, confirming models of cosmic-ray muon production.

Contribution

It provides the most precise measurement to date of the muon charge ratio below 100 GeV and observes an increase at higher momenta, validating cosmic-ray shower models.

Findings

Charge ratio is constant at 1.2766 below 100 GeV

Charge asymmetry increases at momenta above 100 GeV

Results agree with existing cosmic-ray muon production models

Abstract

This paper describes a new measurement of the flux ratio of positive and negative muons from cosmic-ray interactions in the atmosphere, using data collected by the CMS detector at ground level and in the underground experimental cavern. The excellent performance of the CMS detector allowed detection of muons in the momentum range from 3 GeV to 1 TeV. For muon momenta below 100 GeV the flux ratio is measured to be a constant $1.2766 \pm 0.0032(stat) \pm 0.0032(syst)$, the most precise measurement to date. At higher momenta an increase in the charge asymmetry is observed, in agreement with models of muon production in cosmic-ray showers and compatible with previous measurements by deep-underground experiments.