The information from muon arrival time distributions of high-energy EAS as measured with the KASCADE detector KASCADE Collaboration

Using the facilities of the KASCADE Central Detector extensive air showers (EAS) muon arrival time distributions, observed with reference to the arrival time of the first locally registered muon, and their correlations with other EAS observables have been experimentally investigated. The variation of adequately defined time parameters with the distance Rl from the EAS axis has been measured. The experimental data enable a study of the sensitivity of such local arrival time distributions, which characterise the structure of the shower disc, to the mass composition of cosmic rays in the energy region around the knee. For that purpose, non-parametric multivariate even-by-event analyses have been performed for an estimate of the mass composition specified by three different mass groups, invoking detailed Monte Carlo simulations of the EAS development. It turns out that local muon arrival time distributions, without information Corresponding author. E-mail address: [email protected] (A.F. Badea). 1 On leave of absence from National Institute of Physics and Nuclear Engineering, Bucharest, Romania. 2 On leave of absence from University of Lodz, Lodz, Poland. 3 On leave of absence from Moscow State University, Moscow, Russia. 0927-6505/02/$ see front matter 2002 Elsevier Science B.V. All rights reserved. PII: S0927-6505 (02 )00153-6 Astroparticle Physics 18 (2003) 319–331 www.elsevier.com/locate/astropart on the curvature of the shower disc, display a minor sensitivity to the mass of the EAS inducing particle, at least for distances from the shower axis Rl < 100 m. The measurements comprise a subset of all EAS events registered by KASCADE due to the observation conditions of the arrival time distributions, with a threshold of the muon energy Eth 1⁄4 2.4 GeV and a minimum multiplicity nth for being accepted in the observed data samples. This subset is sensitive to variations of the integral EAS muon energy spectrum. By studying the event acceptance in the registered samples on basis of Monte Carlo simulations a test of the consistency of the Monte Carlo simulations with the data is enabled, comparing the results inferred from observations at different Rl and different nth values. Within the present uncertainties the results of such a test show a remarkable agreement of the experimental findings with the Monte Carlo simulations, using the QGSJET model as generator of the high-energy hadronic interactions. 2002 Elsevier Science B.V. All rights reserved. PACS: 98.70.Sa; 96.40.Pq