A thinning method using weight limitation for air-shower simulations

Abstract

The maximum number of particles in a 10 20 eV proton air shower exceeds 10 11. Full simulations are no longer feasible and tracking of a representative sub-sample of particles (so-called “thinning”) has to be introduced. The paper describes the physical and mathematical basis of the thinning algorithms and demonstrates how different thinning methods can be compared. A thinning method using weight limitation is proposed to enhance statistical precision for particle densities at large core distances, where measurements of the highest energy cosmic rays are made. Comparison of the proposed algorithm to the classical Hillas thinning shows an improvement of a factor 10–100 in computing time, depending on the energy, angle of incidence and particle type of the cosmic ray. The proposed thinning method gives consistent results also when single showers are studied, while the classical Hillas thinning can only be used to study average distributions over a number of showers.