Time variations in the deep underground muon flux measured by MACRO
  More than 30 million of high-energy muons collected with the MACRO detector at the underground Gran Sasso Laboratory have been used to search for flux variations of different natures. Two kinds of studies were carried out: search for periodic variations and for the occurrence of clusters of events. Different analysis methods, including Lomb-Scargle spectral analysis and Scan Test statistics have been applied to the data. 
Y. Becherini, S. Cecchini, M. Cozzi, H. Dekhissi, J. Derkaoui, G.   Giacomelli, M. Giorgini, F. Maaroufi, G. Mandrioli, A. M...