Abstract
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-Nc 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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Arnold, P., Gorda, T. & Iqbal, S. The LPM effect in sequential bremsstrahlung: incorporation of “instantaneous” interactions for QCD. J. High Energ. Phys. 2022, 130 (2022). https://doi.org/10.1007/JHEP11(2022)130
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DOI: https://doi.org/10.1007/JHEP11(2022)130