Conversion of photons to dileptons in the Kroll-Wada and parton shower approaches

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Main Authors: Ježo, Tomáš, Klasen, Michael, Neuwirth, Alexander Puck
Format: Preprint
Published: 2025
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author Ježo, Tomáš
Klasen, Michael
Neuwirth, Alexander Puck
author_facet Ježo, Tomáš
Klasen, Michael
Neuwirth, Alexander Puck
contents The study of dileptons in high-energy heavy-ion collisions provides critical insights into the properties of the quark-gluon plasma and the thermal radiation emitted throughout its evolution. In the low-mass region, dileptons originate from both direct photon conversion and hadronic decays, with the Kroll-Wada equation traditionally used to relate direct real and direct virtual photon production. In this work, we explore the possibility of using parton shower event generators to model this conversion process, leveraging their unitary treatment of internal photon conversions that naturally preserves normalisation, as well as their ability to incorporate higher-order corrections, recoil kinematics, and realistic experimental selection criteria. We compare the Kroll-Wada approach to simulations using the Pythia8 simple shower, the Vincia sector shower, and the POWHEG shower matched NLO event generator. Our results reveal that the parton shower approach offers improved accuracy in describing the dilepton spectrum, particularly towards larger invariant masses where phase-space suppression effects become relevant.
format Preprint
id arxiv_https___arxiv_org_abs_2506_23162
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Conversion of photons to dileptons in the Kroll-Wada and parton shower approaches
Ježo, Tomáš
Klasen, Michael
Neuwirth, Alexander Puck
High Energy Physics - Phenomenology
The study of dileptons in high-energy heavy-ion collisions provides critical insights into the properties of the quark-gluon plasma and the thermal radiation emitted throughout its evolution. In the low-mass region, dileptons originate from both direct photon conversion and hadronic decays, with the Kroll-Wada equation traditionally used to relate direct real and direct virtual photon production. In this work, we explore the possibility of using parton shower event generators to model this conversion process, leveraging their unitary treatment of internal photon conversions that naturally preserves normalisation, as well as their ability to incorporate higher-order corrections, recoil kinematics, and realistic experimental selection criteria. We compare the Kroll-Wada approach to simulations using the Pythia8 simple shower, the Vincia sector shower, and the POWHEG shower matched NLO event generator. Our results reveal that the parton shower approach offers improved accuracy in describing the dilepton spectrum, particularly towards larger invariant masses where phase-space suppression effects become relevant.
title Conversion of photons to dileptons in the Kroll-Wada and parton shower approaches
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2506.23162