Title: The LPM effect in sequential bremsstrahlung

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 analyze the case when the coherence lengths of two consecutive splitting processes overlap, which is important for understanding corrections to standard treatments of the LPM effect in QCD. Previous authors have analyzed this problem in the case of overlapping double bremsstrahlung where at least one of the bremsstrahlung gluons is soft. Here we show how to generalize to include the case where both splittings are hard. A number of techniques must be developed, and so in this paper we simplify by (i) restricting attention to a subset of the interference effects, which we call the “crossed” diagrams, and (ii) working in the large-N _c limit. We first develop some general formulas that could in principle be implemented numerically (with substantial difficulty). To make more analytic progress, we then focus on the case of a thick, homogeneous medium and make the multiple scattering approximation (also known as the $$\hat{q}$$ or harmonic approximation) appropriate at high energy. Lastly, we show that the differential rate dΓ/dx dy for overlapping double bremsstrahlung of gluons with momentum fractions x and y can then be reduced to the calculation of a 1-dimensional integral, which we perform numerically.

Authors:

Arnold, Peter ^[1]; Iqbal, Shahin ^[2]

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+ Show Author Affiliations

1. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Physics
2. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Physics; Quaid-i-Azam Univ. Campus, Islamabad (Pakistan)

Publication Date:

2015-04-15

Research Org.:

Univ. of Virginia, Charlottesville, VA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1454511

Grant/Contract Number:  

SC0007984

Resource Type:

Accepted Manuscript

Journal Name:

Journal of High Energy Physics (Online)

Additional Journal Information:

Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2015; Journal Issue: 4; Journal ID: ISSN 1029-8479

Publisher:

Springer Berlin

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quark-Gluon Plasma; QCD