Fragmentation Function in Non-Equilibrium QCD Using Closed-Time Path Integral Formalism

TL;DR

This paper develops a formalism for defining and calculating the fragmentation function in non-equilibrium QCD using the Schwinger-Keldysh closed-time path integral approach, relevant for high-energy nuclear collisions.

Contribution

It introduces a novel non-equilibrium QCD fragmentation function framework using light-cone quantization and closed-time path integrals, incorporating medium effects via Wilson lines.

Findings

Formulation of non-equilibrium fragmentation function in QCD.

Potential inclusion of medium interactions through Wilson line modifications.

Relevance to hadron production in quark-gluon plasma at RHIC and LHC.

Abstract

In this paper we implement Schwinger-Keldysh closed-time path integral formalism in non-equilibrium QCD to the definition of Collins-Soper fragmentation function. We consider a high p_T parton in QCD medium at initial time t_0 with arbitrary non-equilibrium (non-isotropic) distribution function f(\vec{p}) fragmenting to hadron. We formulate parton to hadron fragmentation function in non-equilibrium QCD in the light-cone quantization formalism. It may be possible to include final state interactions with the medium via modification of the Wilson lines in this definition of the non-equilibrium fragmentation function. This may be relevant to study hadron production from quark-gluon plasma at RHIC and LHC.