Multiple Parton Scattering in Nuclei: Parton Energy Loss

TL;DR

The paper addresses how multiple parton scattering in deeply inelastic scattering off nuclei modifies the fragmentation of fast quarks, leading to parton energy loss. It develops a framework based on generalized factorization of twist-four parton distributions to derive modified quark fragmentation functions and their QCD evolution, explicitly including Landau-Pomeranchuk-Migdal interference. The key finding is that interference constrains gluon radiation, producing a softening of fragmentation functions with a quadratic dependence on nuclear size, governed by twist-four matrix elements T^A_{qg}. This work provides a bridge between medium properties and measurable modifications of hadron distributions, with implications for DIS on nuclei and potentially for pA/AA and quark-gluon plasma contexts.

Abstract

Multiple parton scattering and induced parton energy loss is studied in deeply inelastic scattering (DIS) off nuclei. The effect of multiple scattering of a highly off-shell quark and the induced parton energy loss is expressed in terms of the modification to the quark fragmentation functions. We derive such modified quark fragmentation functions and their QCD evolution equations in DIS using generalized factorization of higher twist parton distributions. We consider double-hard, hard-soft parton scattering as well as their interferences in the same framework. The final result, which depends on both the diagonal and off-diagonal twist-four parton distributions in nuclei, demonstrates clearly the Landau-Pomeranchuk-Migdal interference features and predicts a unique nuclear modification of the quark fragmentation functions.

Figures (15)

• Figure 1: Diagram representing the factorized form of the semi-inclusive hadronic tensor $W_{\mu\nu}$.
• Figure 2: Lowest order process that contributes to $H^(0)_{\mu\nu}$.
• Figure 3: The hard partonic part of next-to-leading order process that contributes to $H^{(1)}_{\mu\nu}$.
• Figure 4: A diagram for quark-gluon rescattering processes with three possible cuts, central(C), left(L) and right(R).
• Figure 5: A diagram for the gluon-gluon rescattering process.