Energy loss of fast quarks in nuclei

TL;DR

This paper investigates how fast quarks lose energy while traveling through nuclei by analyzing Drell-Yan dimuon production, revealing the first evidence of nonzero parton energy loss in nuclear matter.

Contribution

It introduces a new formulation of the Drell-Yan process in the nuclear rest frame and measures the first nonzero energy loss of partons in nuclei.

Findings

Energy loss per unit length: -dE/dz = 2.32 ± 0.52 ± 0.5 GeV/fm

First experimental evidence of nonzero parton energy loss in nuclei

Analysis of nuclear dependence ratios versus momentum fraction and mass

Abstract

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of $^2H$, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus the incident proton's momentum fraction and dimuon effective mass. The resulting energy loss per unit path length is $-dE/dz = 2.32 \pm 0.52\pm 0.5$ GeV/fm. This is the first observation of a nonzero energy loss of partons traveling in nuclear environment.