The separation of the particle and light fronts in cosmic ray showers at mountain altitudes

This Thesis describes a study of the time separation of the Cerenkov light and particle fronts in large (10(^16) - 10(^18) eV) cosmic ray air showers at an atmospheric depth of 862 g cm(^-2). The work formed only part of a much larger experiment conducted at the Dugway Proving Ground, Utah, U.S.A. during the autumn and winter months of 1977/8, 1978/79, 1979/80. The aim of this particular work is to refine our understanding of the time delay between the Cerenkov light and the particle fronts, and to establish this time as a depth of maximum sensitive measure. Since this is a prime indicator of the mass of the initiating primary, the time delay which can be readily measured may yield a method of estimating the primary mass of energetic cosmic rays. An account of earlier measurements of Cerenkov radiation is given as well as a theoretical treatment of the time separation based on computer simulations of showers. The experimental results are presented which demonstrate a sensitivity to cascade development and recommendations for future time separation studies are made.