Studies on the atmospheric erenkov radiation from large cosmic ray showers

Abstract

The experiment on which the present investigation is based was conducted at the Cosmic Radiation Research Laboratory, Physics Department, Gauhati University, India, during the autumn and winter seasons of November 1979 to March 1982. EAS of primary energy Epgt 1016eV were selected by an array of GM Counter Trays. The associated optical Cerenkov pulses were detected by a Cerenkov counter comprising of PM tube and parabolic reflec-ting mirror and recorded by CRO and camera arrangement. In about 140 hours of operation, 457 genuine optical pulses were recorded. The distribution of the pulse heights has been compared with analytical and simulation results deduced by the authoress. The experimental pulse height distribution has further been compared with experimental data of other workers. In the analytical solution of the problem, the primary energy has been tacitly eliminated, since energy could not be determined with the present detecting system. Further, con-tributions from vertical as well as inclined showers have been duly considered. Cerenkov pulse height distributions have also been obtained by the method of Monte Carlo Simulation, assuming four different models of primary mass compositions viz., (i) Pure proton, (ii) Constant mixed, (iii) Rigidity cutoff and (iv) Heavy to light in the energy interval 1016-1018eV. The normalised experimental data when compared with these simulation results, give best fit corresponding to primary mass composition having predominantly protons at energies beyond 1016eV.