Drell-Yan and J/psi Production in High Energy Proton-Nucleus and Nucleus-Nucleus Collisions

TL;DR

This paper investigates Drell-Yan and J/psi production in high-energy proton-nucleus and nucleus-nucleus collisions, analyzing nuclear effects like energy degradation, quantum coherence, and absorption, and comparing results across different collision systems.

Contribution

It introduces a coherent framework accounting for quantum coherence and energy loss to explain nuclear effects in Drell-Yan and J/psi production, with consistent coherence time estimates.

Findings

Coherence time of approximately 0.4-0.5 fm/c for particle production.

Absorption cross section of J/psi around 3.6 mb.

Reasonable reproduction of S+U collision data, but not Pb+Pb.

Abstract

The distributions of outgoing protons and charged hadrons in high energy proton-nucleus collisions are described rather well by a linear extrapolation from proton-proton collisions. This linear extrapolation is applied to precisely measured Drell-Yan cross sections for 800 GeV protons incident on a variety of nuclear targets. The deviation from linear scaling in the atomic number A can be accounted for by energy degradation of the proton as it passes through the nucleus if account is taken of the time delay of particle production due to quantum coherence. We infer an average proper coherence time of 0.4 +/- 0.1 fm/c. Then we apply the linear extrapolation to measured J/psi production cross sections for 200 and 450 GeV/c protons incident on a variety of nuclear targets. Our analysis takes into account energy loss of the beam proton, the time delay of particle production due to quantum coherence, and absorption of the J/psi on nucleons. The best representation is obtained for a coherence time of 0.5 fm/c, which is consistent with Drell-Yan production, and an absorption cross section of 3.6 mb, which is consistent with the value deduced from photoproduction of the J/psi on nuclear targets. Finally, we compare to recent J/psi data from S+U and Pb+Pb collisions at the SPS. The former are reproduced reasonably well with no new parameters, but not the latter.