The Atmospheric Muon Charge Ratio at the MINOS Near Detector

TL;DR

This paper reports a precise measurement of the atmospheric muon charge ratio using the MINOS near detector, providing insights into cosmic ray interactions and decay processes.

Contribution

It presents the first high-precision charge ratio measurement at the MINOS near detector, reducing systematic errors through data combination with opposite magnetic polarities.

Findings

Measured charge ratio of 1.2666 with small statistical and systematic uncertainties.

Results are consistent with the world average but lower than previous MINOS far detector measurements.

Supports the hypothesis that kaon decay contributes significantly to muon production.

Abstract

The magnetized MINOS near detector can accurately determine the charge sign of atmospheric muons, this facilitates a measurement of the atmospheric muon charge ratio. To reduce the systematic error associated with geometric bias and acceptance we have combined equal periods of data obtained with opposite magnetic field polarities. We report a charge ratio of $1.2666\pm0.0015(stat.)^{+0.0096}_{-0.0088}(syst.)$ at a mean E$_{\mu,0}cos(\theta)$=\unit[63]{GeV}. This measurement is consistent with the world average\cite{Hebbeker}\cite{Haino}\cite{Achard} but significantly lower than the earlier observation at the MINOS far detector\cite{Adamson}. This increase is shown to be consistent with the hypothesis that a greater fraction of the observed muons arise from kaon decay within the cosmic ray shower.