arXiv : Gluon Radiation from a classical point particle II: dense gluon fields

Kajantie, K.; McLerran, Larry D.; Paatelainen, Risto

doi:10.1103/PhysRevD.101.054012

Article
Report number	arXiv:1911.12738 ; CERN-TH-2019-201 ; HIP-2019-37/TH ; INT-PUB-19
Title	Gluon Radiation from a classical point particle II: dense gluon fields
Author(s)	Kajantie, K. (Helsinki U.) ; McLerran, Larry D. (Washington U., Seattle) ; Paatelainen, Risto (Helsinki U. ; CERN)
Publication	2020-03-11
Imprint	2019-11-28
Number of pages	18
Note	36 pages, 8 figures
In:	Phys. Rev. D 101 (2020) 054012
DOI	10.1103/PhysRevD.101.054012
Subject category	nucl-th ; Nuclear Physics - Theory ; hep-ph ; Particle Physics - Phenomenology
Abstract	The goal of this paper is to extend the results of Ref. [1], where formulae were derived for gluonic radiation for a high energy nucleus colliding with a classical colored particle. In Ref. [1], we computed the amplitudes for radiation in the fragmentation region of the particle for a dilute gluonic field. In this paper, we compute the radiation by solving the fluctuation equations of the dense background field in a specific gauge which makes it simple to solve the asymptotic radiation from an initial condition immediately after the passage of the nucleus. We identify and compute two components of gluon radiation, a bulk component which extends to the central region and bremsstrahlung, which may give rise to an experimentally observable intensity peak in the target fragmentation region.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2020-2025 authors (License: CC-BY-4.0)

$\small Nucleus $A$ moving along the light-cone $x^-=0$ collides with a static quark in the origin, interacts with its color electric field and accelerates it to a constant momentum (thick lines). The nuclear vacuum equivalent background color field in LC gauge $A^-=0$ is chosen so that it is nonzero at $x^-<0$ before the collision (light blue area) and zero after it. The asymptotic color fluctuation field, which gives the gluon distribution, can then be simply solved from initial conditions formulated at $x^-=\epsilon\to0$.$ $\small A plot of $k_T^4 N(k_T,y=0)$ computed from \eq\nr{bulkspectranum} for $y=0$ and for the correlator $S$ computed for $Q^A_s=2$ and $m_{\rm IR} =0.2$. The red curve is the logarithmic approximation in \eq\nr{loga}.$ $\small A plot of $k_T^4 N(k_T,y)$ computed from \eq\nr{bulkspectranum} for values of $y$ maked in the figure and for $Q^A_s=2$ and $m_{\rm IR} =0.2$ (left panel). The red dashed curve is the analytic large $k_T$ approximation \eq\nr{ydepeq} for $y=6$. The blue dashed curve is the $y\to\infty$ limit \eq\nr{dNCR}. The right panel shows the $y$ dependence for $k_T=2, 10$ and for the same $Q_s^A,\,m_{\rm IR}$. The red dashed curve is the analytic approximation in \eq\nr{ydepeq}. The curves are proportional to $(Q^A_s)^2$.$ Show more plots

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