Seasonal Variation of the Underground Cosmic Muon Flux Observed at Daya Bay

TL;DR

This study measures the seasonal variation of underground cosmic muon flux at Daya Bay, showing a positive correlation with atmospheric temperature and quantifying this relationship across three underground halls over two years.

Contribution

It provides the first detailed measurement of seasonal muon flux variation and temperature correlation at Daya Bay's underground halls with specific correlation coefficients.

Findings

Muon flux varies seasonally with temperature.

Correlation coefficients differ among the three halls.

Data covers a two-year period.

Abstract

The Daya Bay Experiment consists of eight identically designed detectors located in three underground experimental halls named as EH1, EH2, EH3, with 250, 265 and 860 meters of water equivalent vertical overburden, respectively. Cosmic muon events have been recorded over a two-year period. The underground muon rate is observed to be positively correlated with the effective atmospheric temperature and to follow a seasonal modulation pattern. The correlation coefficient $\alpha$, describing how a variation in the muon rate relates to a variation in the effective atmospheric temperature, is found to be $\alpha_{\text{EH1}} = 0.362\pm0.031$, $\alpha_{\text{EH2}} = 0.433\pm0.038$ and $\alpha_{\text{EH3}} = 0.641\pm0.057$ for each experimental hall.