Pair invariant mass spectrum and polarization asymmetry in the event generation of gamma-ray conversions

TL;DR

This paper introduces a Geant4 physics model for simulating gamma-ray conversions, focusing on dielectron invariant mass spectra and polarization asymmetry, to improve background simulations in particle physics experiments.

Contribution

The paper presents a new five-dimensional Bethe-Heitler differential cross section model implemented in Geant4 for more accurate gamma-ray conversion simulations.

Findings

The model accurately reproduces analytical expressions.

It addresses background simulation issues in LHC and Belle II.

Enhances understanding of gamma-ray conversion properties.

Abstract

We examine the dielectron invariant mass spectrum and the variation of the polarization asymmetry as a function of that mass in the event generator of the five-dimensional Bethe-Heitler differential cross section of the conversion of linearly polarized photons that we have implemented recently as a Geant4 Physics Model. We compare the results obtained with simulated samples to analytical expressions. Studies of $b \to s \gamma$ decays at LHC and Belle II experiments could provide hints of physics beyond the standard model in flavor-changing neutral current processes; issues have been reported in the simulation of the properties of the background induced by genuine $\gamma$-ray conversions in their detectors. Our results demonstrate that using the five-dimensional model would help solve these issues.