Systematic analysis of the incoming quark energy loss in cold nuclear matter

TL;DR

This paper analyzes quark energy loss in cold nuclear matter using experimental data, determining the energy loss rate and examining its dependence on path length, with implications for understanding parton propagation.

Contribution

It provides a leading order statistical analysis of experimental data to estimate quark energy loss parameters, challenging some theoretical predictions.

Findings

Quark energy loss per unit length is approximately 1.21 GeV/fm.

Data rules out significant energy loss at lower incident energies.

Linear or quadratic path length dependence cannot be distinguished with current data.

Abstract

The investigation into the fast parton energy loss in cold nuclear matter is crucial for a good understanding of the parton propagation in hot-dense medium. By means of four typical sets of nuclear parton distributions and three parametrizations of quark energy loss, the parameter values in quark energy loss expressions are determined from a leading order statistical analysis of the existing experimental data on nuclear Drell-Yan differential cross section ratio as a function of the quark momentum fraction. It is found that with independence on the nuclear modification of parton distributions, the available experimental data from lower incident beam energy rule out the incident-parton momentum fraction quark energy loss. Whether the quark energy loss is linear or quadratic with the path length is not discriminated. The global fit of all selected data gives the quark energy loss per unit path length {\alpha} = 1.21\pm0.09 GeV/fm by using nuclear parton distribution functions determined only by means of the world data on nuclear structure function. Our result does not support the theoretical prediction: the energy loss of an outgoing quark is three times larger than that of an incoming quark approaching the nuclear medium. It is desirable that the present work can provide useful reference for the Fermilab E906/SeaQuest experiment.