Estimating a cosmic ray detector exposure sky map under the hypothesis of seasonal and diurnal effects factorization

TL;DR

This paper introduces a method to accurately estimate cosmic ray detector exposure maps by factoring seasonal and diurnal environmental effects, improving anisotropy measurements in cosmic ray arrival directions.

Contribution

It proposes a novel empirical approach to correct for environmental variations assuming factorization of seasonal and diurnal effects, enhancing exposure map accuracy.

Findings

Method successfully tested on a model detector with atmospheric-dependent aperture

Achieves sub-1% accuracy in exposure map estimation

Improves the reliability of large-scale anisotropy measurements in cosmic rays

Abstract

The measurement of large scale patterns or anisotropies in the arrival direction of high energy cosmic rays is an important step towards the understanding of their origin. Such measurements rely on an accurate estimation of the detector relative exposure in each direction on the sky : the coverage map. To reach an accuracy on the determination of this map below the one percent level one must properly identify and correct for all the environmental effects that may induce variations in the detector exposure as a function of time. In an approach, similar to the one used in anti-sidereal time analysis, we propose a method to empirically estimate and correct for those effects under the hypothesis that seasonal and diurnal variations can be factorized. We tested this method using a model ground detector of cosmic ray air showers, whose aperture varies due to the dependence of the air shower development on the atmospheric conditions.