Testing the energy resolution capabilities of the Compton And Two Photons Spectrometer

Abstract

The nuclear equation of state describes the properties and formation of large astrophysical objects, notably neutron stars. It can be constrained with the density dependence of the symmetry energy, which is modelled to have a linear correlation with neutron skin thickness. Neutron skin thickness can be studied with parity-violating electron scattering experiments, which have a systematic error that can be constrained by measuring beam-normal single-spin asymmetries. Experimental measurements of such asymmetries agree with theoretical values, but the theoretical values have an error of 20% due to a poorly known Compton form factor, which is a function of the energy deposited into the target in elastic Compton scattering. Because of this, it is necessary to separate elastic and inelastic Compton scattering events. CATSis alarge NaI(Tl) scintillating detector that will be used to study the Compton form factor at the A2 Collaboration in Mainz, Germany. Two Geant4 simulations of CATS were built, and using results from Ref. [Wis94], efficiency and contamination were calculated for a range of energies with one of these simulations. This was done by estimating the ratio of elastic to inelastic photons produced at a variety of energies for Compton scattering off of a 12C target. Then, based on the estimated ratio, photons at energies associated with elastic and inelastic Compton scattering off of a 12C target were fired into the core of the CATS simulation. Additionally, CATS was used for the first time in years to collect cosmic ray data for an overnight run in Mainz in July of 2022 for testing purposes.