Opportunities with Drell-Yan Scattering at Fermilab

Abstract

The proton is a composite object made of fundamental, strongly-interacting quarks. Many of the features of the proton can be described by a simple picture based on three valence quarks bound by the exchange of gluons. However, protons are much more complex objects with the vast majority of their mass dynamically generated by the strong force and manifest in the sea quark and gluon distributions. While deep inelastic scattering cannot differentiate between quark and antiquarks, the Drell-Yan process inherently involves the antiquark distributions of either the beam or target hadron. By measuring Drell-Yan scattering, the Fermilab E-906/SeaQuest experiment will study the sea quarks in the proton and in nuclei. The primary goals of this measurement include elucidating the anti-d to anti-u quark asymmetry in the proton and a study of the EMC effect in sea quarks. With the same data, the angular distribution of Drell-Yan scattering will be studied. Previous measurements of these distributions have been interpreted as evidence for transverse momentum dependent Boer-Mulders h⊥1 distribution; although, pion and proton induced Drell-Yan data disagree. The increased statistical precision of the anticipated data will allow for better extraction of the angular distributions. To accomplish these goals, the experiment will use a 120 GeV proton beam extracted from the Fermilab Main Injector. While the experiment will be taking advantage of equipment from earlier Drell-Yan experiments, the changes in kinematics of the experiment require several, significant upgrades to the spectrometer. The collaboration expects to begin data collection in late fall of 2010.