Nuclear Suppression of Dileptons at Large xF

TL;DR

This paper investigates the nuclear suppression of dilepton production at large xF in proton-nucleus collisions, attributing it to energy conservation in multiple parton rescatterings rather than coherence effects, and confirms this with experimental data and predictions.

Contribution

It demonstrates that nuclear suppression at large xF is governed by energy conservation in rescatterings, challenging the coherence-based explanations.

Findings

Good agreement with E772 experimental data

Predictions of nuclear suppression at RHIC energies

Suppression mechanism explained by energy conservation

Abstract

We study a significant nuclear suppression of the relative production rates (p(d)+A)/(p+d(p)) for the Drell-Yan process at large Feynman xF. Since this is the region of minimal values for the light-front momentum fraction variable x2 in the target nucleus, it is tempting to interpret this as a manifestation of coherence or of a Color Glass Condensate. We demonstrate, however, that this suppression mechanism is governed by the energy conservation restrictions in multiple parton rescatterings in nuclear matter. To eliminate nuclear shadowing effects coming from the coherence, we calculate nuclear suppression in the light-cone dipole approach at large dilepton masses and at energy accessible at FNAL. Our calculations are in a good agreement with data from the E772 experiment. Using the same mechanism we predict also nuclear suppression at forward rapidities in the RHIC energy range.