A method for energy estimation and mass composition determination of primary cosmic rays at the Chacaltaya observation level based on the atmospheric Cherenkov light technique

Abstract

A new method for energy and mass composition estimation of primary cosmic rays based on the atmospheric Cherenkov light flux in extensive air showers (EAS) is proposed. The Cherenkov light flux in EAS initiated by primary protons and iron nuclei is simulated with the CORSIKA 5.62 code for the Chacaltaya observation level (536g/cm2) in the energy range 10TeV–10PeV. An adequate model for the lateral distribution of Cherenkov light in showers is obtained. Using the model and a solution for the overdetermined system of nonlinear equations based on the Gauss–Newton method with autoregularization, two different detector arrangements are compared. The accuracies in energy and shower axis determination are studied and the corresponding selection criteria are proposed. An approximation with a nonlinear fit is obtained and the energy dependence of the proposed model parameters is studied. A detailed study of the model parameters as a function of the primary energy is made. This permits, taking into account the properties of the proposed method and the strong nonlinearity of the model, a distinction to be made between proton and iron primaries. The detector response for the detector sets is simulated and the accuracies in energy determination are calculated. In addition, the accuracies in shower axis determination are studied and criteria for shower axis position estimation are proposed.