Study of multi-muon bundles in cosmic ray showers detected with the DELPHI detector at LEP

TL;DR

This study uses the DELPHI detector at LEP to analyze multi-muon bundles from cosmic ray air showers, revealing discrepancies between observed data and Monte Carlo predictions, especially for high multiplicity events.

Contribution

It provides the first detailed measurement of multi-muon bundles with the DELPHI detector and evaluates the performance of the QGSJET01 model in predicting such events.

Findings

QGSJET01 underestimates high multiplicity muon events.

Muon multiplicity distribution shows significant deviation from model predictions.

Data collected over 1.6 million seconds with underground muon detection.

Abstract

The DELPHI detector at LEP has been used to measure multi-muon bundles originating from cosmic ray interactions with air. The cosmic events were recorded in ``parasitic mode'' between individual e+e- interactions and the total live time of this data taking is equivalent to 1.6x10^6 seconds. The DELPHI apparatus is located about 100 metres underground and the 84 metres rock overburden imposes a cut-off of about 52 GeV/c on muon momenta. The data from the large volume Hadron Calorimeter allowed the muon multiplicity of 54201 events to be reconstructed. The resulting muon multiplicity distribution is compared with the prediction of the Monte Carlo simulation based on CORSIKA/QGSJET01. The model fails to describe the abundance of high multiplicity events. The impact of QGSJET internal parameters on the results is also studied.