Underground flux of atmospheric muons and its variations with 25 years of data of the LVD experiment

Abstract

The Large Volume Detector (LVD) is a 1 kton liquid scintillator detector located at Laboratori Nazionali del Gran Sasso, Italy, at the average depth of 3600 m w.e. The experiment has been continuously taking data since June 1992. The muon dataset collected by LVD over 25 years (from 1992 to 2016) consists of 5.5·107 events, being the largest ever provided by a single detector underground. The analysis of the global time series shows a modulation of muon flux underground with period of T = (365.1±0.2)days, an amplitude of 1.5% and a maximum at the beginning of July. A clear correlation with atmospheric temperature variations is present, with a measured coefficient of αT = 0.93±0.02. This is in agreement with the expected value at LVD depth and with the value measured by other experiments in the same underground site.