Detection of muon bundles from cosmic ray showers by the DELPHI experiment

Multi-muon bundles, originated from cosmic ray interactions in the atmosphere, have been detected by the DELPHI detector at LEP. Data have been taken since the year 1998 when the dedicated cosmic trigger was implemented. The aim is to measure muon multiplicity distribution over a wide range of multiplicities using signals of streamer tubes inside DELPHI hadron calorimeter. The measurement is compared with prediction of the QGSJET model implemented to the CORSIKA simulation package.