Cosmic multi-muon bundles detected by DELPHI

The DELPHI detector at LEP, located 100 m underground, has been used to detect multi-muon bundles originated from cosmic ray interactions in the atmosphere. The cosmic events registered during the years 1999 and 2000 correspond roughly to 1.6 106 s of effective run time. The muon multiplicity distribution has been measured over a wide range of multiplicities. This paper provides a preliminary comparison between the data and a prediction of the QGSJET model implemented to the CORSIKA simulation package.