..., the primary focus of this experiment was to measure the asymmetry of down and up antiquarks in the nucleon sea using Drell-Yan di-muons. The first Drell-Yan experiment was performed on E-866/NuSea at Fermilab with 800-GeV proton beam interactions with liquid hydrogen and deuterium targets. To extend these measurements to larger Bjorken-x, E-906/SeaQuest has been approved by Fermilab. It will use a 120 GeV proton beam extracted from the Fermilab Main Injector instead. In addition to extending the down to up antiquark measurements, the experiment will also examine the modifications to the antiquark structure of the proton from nuclear binding.
The Drell–Yan process occurs in high energy hadron–hadron scattering. It takes place when a quark of one hadron and an antiquark of another hadron annihilate, creating a virtual photon or Z boson which then decays into a pair of oppositely-charged leptons. This process was first suggested by Sidney Drell and Tung-Mow Yan in 1970 to describe the production of lepton-antilepton pairs in high-energy hadron collisions. Experimentally, this process was first observed by J.H. Christenson et al. in proton–uranium collisions at the Brookhaven National Laboratory, Alternating Gradient Synchrotron.