Disentangling Shadowing from Coherent Energy Loss using the Drell-Yan Process

TL;DR

This paper proposes using Drell-Yan lepton pair measurements in p-Pb collisions at the LHC to distinguish between shadowing and coherent energy loss effects in quarkonium production, providing a clearer understanding of nuclear modifications.

Contribution

It introduces a method to disentangle shadowing from coherent energy loss in quarkonium production using the DY to J/psi suppression ratio at the LHC.

Findings

Shadowing effects cancel out in the DY/J/psi suppression ratio.

Coherent energy loss remains significant in the ratio.

Measurement feasible at forward rapidity with existing LHC detectors.

Abstract

We suggest the measurement of Drell-Yan (DY) lepton pairs in p-Pb collisions at the LHC (sqrt(s)=5.02 TeV) in order to disentangle the relative contributions of shadowing and coherent energy loss in quarkonium production off nuclei. The nuclear modification of low mass DY production is computed at NLO using various sets of nuclear parton densities. It is then observed that shadowing effects strongly cancel out in the J/psi over DY suppression ratio R_{pA}^{J/psi}(y) / R_{pA}^{DY}(y), unlike the effect of coherent energy loss. Such a measurement could be performed at forward rapidity by the ALICE and LHCb collaborations at the LHC.