Seasonal variations of the rate of multiple-muons in the Gran Sasso underground laboratory

TL;DR

This paper analyzes seasonal variations in multiple-muon rates at Gran Sasso, revealing a summer peak contrary to previous findings at MINOS, which may be due to latitude-related atmospheric temperature differences, impacting dark matter searches.

Contribution

It provides the first re-analysis of MACRO data showing a summer peak in multiple-muon rates at Gran Sasso, contrasting with MINOS results and suggesting latitude influences muon seasonal modulation.

Findings

Multiple-muon rate peaks in summer at Gran Sasso.

Contrasts with MINOS findings of winter peaks.

Implications for dark matter seasonal modulation studies.

Abstract

It is well known that the rate of cosmic ray muons depends on the atmospheric temperature, and that for events with a single muon the peak of the rate is in summer, in underground laboratories in the northern hemisphere. In 2015 the MINOS experiment, in USA, found that, for small distances between the multiple-muons, the rate of multiple-muons peaks in the winter and that the amplitude of the modulation is smaller than in the case of a single muon. I have done a re-analysis of data of the past MACRO experiment. The result is that under Gran Sasso the rate of multiple-muons at small distances peaks in the summer. This difference with MINOS could be explained by differences in the atmospheric temperature due to latitude. This results could be of interest for dark matter experiments looking to dark matter seasonal modulation due to the Earth's motion.