Hunting for an EMC-like effect for antiquarks

TL;DR

This paper explores the potential for an EMC-like modification of antiquark distributions in nuclei through Drell-Yan processes, analyzing recent experimental data and proposing optimal kinematic conditions for future observations.

Contribution

It suggests the possibility of an antiquark EMC-like effect in nuclei and discusses how current data challenge traditional nuclear effect explanations, proposing specific measurements to confirm this.

Findings

Preliminary data are inconsistent with Fermi motion and energy loss scenarios.

Data suggest a modification of antiquark distributions similar to the EMC effect.

Optimal measurements are proposed for specific kinematic ranges.

Abstract

We argue that the Drell-Yan process in the $x_A \ge 0.15$ kinematics recently studied at FNAL by the E906/SeaQuest experiment may allow to observe an analogous of the EMC effect for antiquarks. The effects of Fermi motion and energy loss are considered. The preliminary E906/SeaQuest data are inconsistent with the growth of the $\sigma_A/A\sigma_N$ ratio expected in the Fermi motion scenario at $x_A \ge 0.25$. The pattern of the $x_A$ dependence of the ratio seems also inconsistent with a scenario in which the dominant nuclear effect is a suppression of the cross section due to the energy loss experienced by a quark of the projectile proton involved in the Drell-Yan process. All together the data suggest the possibility of a modification of the antiquark parton distributions in nuclei, with a pattern similar to the one observed in the EMC effect. We argue that optimal kinematics to look for an antiquark EMC-like effect would be to measure the $\sigma_A^{DY}/A\sigma_N^{DY}$ ratios for $x_A$ = 0.2-0.4 and $x_p$ $\approx$ constant.