Stabilizing energy reconstructions of the surface detector at the Pierre Auger Observatory

Abstract

At the Pierre Auger Observatory, ultra-high energy cosmic rays are measured through indirect measurements of the extensive air showers they induce. Accordingly, an energy reconstruction process must be undertaken. For the surface detector, the models utilized for energy reconstruction are empirical approximations of the true particle distribution and thus, different models should return similar energy reconstructions. However, differing models, particularly at high energies and low zenith angles, do not yield the same energy. The focus of this thesis is to remedy these instabilities; a method was explored using the well-established Nishimura-Kamata-Greisen and Power Law functions. As instabilities are products of geometrical effects leading to poor constrainment of the energy estimator 1000 m from the shower axis, this thesis explores reconstructions using the signal at 1500 m, but, finding the instabilities exacerbated, separate reconstructions for the different geometric occurrences were conducted. Investigating the golden hybrid events, this method was found to reduce instabilities between LDFs and energy estimators.