gamma-ray telescopes using conversions to electron-positron pairs: event generators, angular resolution and polarimetry

TL;DR

This paper evaluates different event generators for gamma-ray pair-conversion telescopes, highlighting their impact on angular resolution and polarization measurement accuracy, crucial for high-resolution gamma-ray astronomy.

Contribution

It benchmarks and validates event generators against an exact model, analyzing their effects on angular resolution and polarization detection in gamma-ray telescopes.

Findings

Generator choice influences angular resolution estimates.

Current generators inadequately model linearly polarized photon sources.

Validation against an exact 5D differential cross-section provides a reference.

Abstract

We benchmark various available event generators in Geant4 and EGS5 in the light of ongoing projects for high angular-resolution pair-conversion telescopes. We compare the distributions of key kinematic variables extracted from the geometry of the three final state particles. We validate and use as reference an exact generator using the full 5D differential cross-section of the conversion process. We focus in particular on the effect of the unmeasured recoiling nucleus on the angular resolution. We show that for high resolution trackers, the choice of the generator affects the estimated resolution of the telescope. We also show that the current available generator are unable to describe accurately a linearly polarised photon source.