Drell-Yan Experiment: Studying Anti-Quarks in the Proton

Abstract

The internal structure of the proton is one of the most vital topic in the present hadron physics. At a high-energy scale the proton reveals its complicated parton structure which is beyond the scope of the Quark Parton Model (QPM), i.e. quarks (q), anti-quarks (q̄) and gluons (g). Gluons and anti-quarks are dynamically created via q → q + g and g → q + q̄, respectively. The dynamics of the proton structure is being investigated in both experiment and theory.The Drell-Yan process in proton+proton collisions is the reaction in which a quark in one proton and an anti-quark in the other proton annihilate into a virtual photon and then create a muon pair: q + q̄ → γ* → μ+ + μ−. This process is suited to study the anti-quarks in the proton, and many experiments measuring the Drell-Yan process have been carried out in the past 20 years. The E906/SeaQuest experiment at Fermi National Accelerator Lab (FNAL) in USA is a Drell-Yan experiment being prepared now to explore a new kinematic region with very high statistics. The main purpose of this experiment is to precisely measure the asymmetry of ū and d̄ distributions in the proton at the xBj range from 0.25 to 0.45.In this paper, the anti-quark flavor asymmetry in the proton and the past Drell-Yan experiments are summarized, and the status of the E906 experiment is reported.