The LPM effect in sequential bremsstrahlung: incorporation of “instantaneous” interactions for QCD

Peter Arnold (Department of Physics, University of Virginia, Charlottesville, VA, 22904, U.S.A.) ; Tyler Gorda (Technische Universität Darmstadt, Department of Physics, Darmstadt, 64289, Germany; ExtreMe Matter Institute EMMI and Helmholtz Research Academy for FAIR, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, 64291, Germany) ; Shahin Iqbal (National Centre for Physics, Quaid-i-Azam University Campus, Islamabad, 45320, Pakistan; Institute of Particle Physics, Central China Normal University, Wuhan, 430079, China)

The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths (formation lengths) of two consecutive splitting processes overlap, avoiding soft-emission approximations. Previous work made a “nearly-complete” calculation of the effect of overlapping formation times on gluonic splittings such as g → gg → ggg (with simplifying assumptions such as an infinite QCD medium and the large-N c limit). In this paper, we extend those previous rate calculations from nearly-complete to complete by including processes involving the exchange of longitudinally-polarized gluons. In the context of Lightcone Pertubation Theory, used earlier for the “nearly-complete” calculation, such exchanges are instantaneous in lightcone time and have their own diagrammatic representation.

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      "value": "The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths (formation lengths) of two consecutive splitting processes overlap, avoiding soft-emission approximations. Previous work made a \u201cnearly-complete\u201d calculation of the effect of overlapping formation times on gluonic splittings such as g \u2192 gg \u2192 ggg (with simplifying assumptions such as an infinite QCD medium and the large-N c limit). In this paper, we extend those previous rate calculations from nearly-complete to complete by including processes involving the exchange of longitudinally-polarized gluons. In the context of Lightcone Pertubation Theory, used earlier for the \u201cnearly-complete\u201d calculation, such exchanges are instantaneous in lightcone time and have their own diagrammatic representation."
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Published on:
23 November 2022
Publisher:
Springer
Published in:
Journal of High Energy Physics , Volume 2022 (2022)
Issue 11
Pages 1-34
DOI:
https://doi.org/10.1007/JHEP11(2022)130
arXiv:
2209.03971
Copyrights:
The Author(s)
Licence:
CC-BY-4.0

Fulltext files: