Measurement of the cosmic muon annual and diurnal flux variation with the COSINE-100 detector

TL;DR

This study measures annual and diurnal variations in cosmic muon flux underground, finding a correlation with atmospheric temperature and confirming the expected seasonal pattern, while no significant daily variation was detected.

Contribution

First measurement of both annual and diurnal cosmic muon flux variations at Y2L using COSINE-100 data, with analysis of atmospheric temperature correlation and diurnal modulation search.

Findings

Muon rate correlates with atmospheric temperature (α_T = 0.80 ± 0.11)

No significant diurnal muon flux variation detected

Results consistent with atmospheric meson production models

Abstract

We report measurements of annual and diurnal modulations of the cosmic-ray muon rate in the Yangyang underground laboratory (Y2L) using 952 days of COSINE-100 data acquired between September 2016 and July 2019. A correlation of the muon rate with the atmospheric temperature is observed and its amplitude on the muon rate is determined. The effective atmospheric temperature and muon rate variations are positively correlated with a measured effective temperature coefficient of $\alpha_{T}$ = 0.80 $\pm$ 0.11. This result is consistent with a model of meson production in the atmosphere. We also searched for a diurnal modulation in the underground muon rate by comparing one-hour intervals. No significant diurnal modulation of the muon rate was observed.