Study of primary cosmic ray composition based on deep underground multiple muons observed in macro.

摘要

The MACRO (Monopole, Astrophysics, and Cosmic Ray Observatory) detector is the largest area deep underground muon detector in the world, capable of observing coincident muons separated by 72 m. Analysis of such multiple muon events yields information about the chemical composition of cosmic ray primaries of energies greater than 100 TeV/nucleus. The distributions of multiplicities and pair separations from 157 days of live-time have been compared to predictions from Monte Carlo simulations assuming different primary compositions. Simulations based on the parameterizations of Forti et al. under-predict the rate of events at large separations. Studies using results from full air shower simulations, which use the HEMAS (High Energy Muons in Air Showers) Monte Carlo program, show a preference for simulations assuming a high energy primary composition of mostly light nuclei. A light composition differs from expectations of traditional acceleration and confinement mechanisms. Further work is required to reduce uncertainties in the simulations, and more measurements must be made to better determine the chemical composition of cosmic ray primaries. ftn*All degree requirements completed in 1993, but degree will be granted in 1994.