Measurement of the charge ratio of atmospheric muons with the CMS detector

TL;DR

This paper reports a highly precise measurement of the positive to negative muon flux ratio from cosmic rays using the CMS detector at CERN, covering a wide momentum range and confirming model predictions.

Contribution

It provides the most precise measurement to date of the atmospheric muon charge ratio across a broad momentum spectrum, utilizing CMS data at ground and underground levels.

Findings

Surface flux ratio measured as 1.2766 ± 0.0045, independent of momentum below 100 GeV/c.

Data at higher momenta suggest an increasing charge ratio, aligning with cosmic ray models.

Results are consistent with previous underground measurements and theoretical predictions.

Abstract

We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interactions in the atmosphere, using data collected by the CMS detector both at ground level and in the underground experimental cavern at the CERN LHC. Muons were detected in the momentum range from 5 GeV/c to 1 TeV/c. The surface flux ratio is measured to be 1.2766 \pm 0.0032(stat.) \pm 0.0032 (syst.), independent of the muon momentum, below 100 GeV/c. This is the most precise measurement to date. At higher momenta the data are consistent with an increase of the charge ratio, in agreement with cosmic ray shower models and compatible with previous measurements by deep-underground experiments.