The arrival time distribution of muons in extensive air showers

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Abstract
The longitudinal structure of the muon disc has been studied up to distances of 60 m from the shower axis by measuring the relative arrival times between single muons in extensive air showers with particle numbers of 1*105 to 2*107. A rather constant thickness of the shower disc was found up to 60 m from the shower axis. The longitudinal distribution up to 30 m from the shower axis is not in agreement with the results from a shower model with a fairly high multiplicity rule for secondary particle formation in hadron interactions. It is highly improbable that this discrepancy is due to inaccuracies in the measurements and contamination by the hadron and electron components. Heavy primaries also do not explain the results. The conclusion is that many more nucleons may be formed in hadron interactions than the model predicts or that massive particles may be formed in the first few collisions of shower development. Further, there is no indication that this discrepancy has any connection with the knee in the primary energy spectrum, which would be expected if a change in the interaction mechanism occurred in this energy region.