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

Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, via E.Fermi 40 - 00044 Frascati, Italy

^a e-mail: francesco.ronga@lnf.infn.it

Published online: 23 March 2017

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.