K. Kobayakawa

Angular resolution of the Ohya air shower detector

Accurate measurements of the total number of muons in an air shower are important for the discrimination of showers produced by astronomical gamma rays from those produced by protons. In order to perform this discrimination, muon detectors with a total area of about 400 m2 have been constructed in the Ohya stone mine. At ground level, scintillation detectors have been distributed for determining the total number of electrons in the air shower. The arrival direction of the air shower determined by usual timing information was examined using independent data on the arrival direction determined by muons in the shower. The angular resolution thus obtained at the shower maximum is 1.7° in the south-north plane and 2° in the east-west plane. The difference of the resolution is due to the asymmetric arrangement of scintillation detectors.

A Study of the Contribution of Prompt Cosmic Ray Muons to Total Muon Fluxes

The contribution of prompt cosmic-ray muons from charmed particles to the conventional muons from pi and K mesons is investigated. The inclusive cross sections for charmed-particle production are given in both non-diffractive and diffractive processes of primary-air collisions. The minimum contribution is determined by charmed-particle production only in non-diffractive processes. On the other hand, the maximum contribution is estimated by stressing the diffractive characters of the charmed particles produced. By solving the diffraction equations including the above cross sections, the energy spectra of the prompt cosmic-ray muons at sea level are given. The integral intensities of maximum and minimum prompt muons are equal to the vertical conventional one at about 15 and 290 TeV, respectively.