High-energy hadrons in extensive air showers

Abstract

Various attempts to interpret the experimental results on high-energy hadrons in extensive air showers of size ∼10⁵-10⁶ at mountain altitudes in terms of the characteristics of high-energy particle interactions have yielded ambiguous results due to apparently large differences between results from different experiments using different types of hadron detectors. In an attempt to understand these differences we have studied the response of different types of detectors to showers with multiple hadrons incident over the detector area. Our simulations suggest that large-area nnonvisual detectors overestimate the energies of high-energy hadrons. The energy overestimation depends on the type and the size of the detector, the energy of the high-energy hadron, the shower size, and the observational altitude. We discuss the results from our experiment at mountain altitude laboratory at Ooty where we have studied this problem by comparing the response of a burst detector placed inside a multiplate cloud chamber with the visual information from the chamber. Our observations show that large discrepancies between the results from different experiments are mostly due to the differences between the response functions of the detectors and that measurements with visual detectors give the most reliable data on the number of high-energy hadrons in air showers. We also show that three experiments which have used burst detectors agree well with each other and with the cloud-chamber experiment if appropriate corrections are applied. We have compared these measurements with the expectations from Monte Carlo simulations of air showers using scaling models for high-energy particle interactions and find that the observed number of hadrons in a shower are too few compared to the expected number. We show that changes in the interaction model which affect only particles in the central region do not have any significant effect on the expected number of high-energy hadrons in a shower. These results imply that either hadron - air-nucleus collisions are very different at high energies ∼10⁶ GeV in the fragmentation region compared to hadron-hadron collisions or there is substantial violation of scaling in the fragmentation region in hadron-hadron interactions at air-shower energies.