Parton Dynamics Inferred from High-Mass Drell-Yan Dimuons Induced by 120 GeV p+D Interactions

摘要

Fermilab Experiment 906/SeaQuest (E906/SeaQuest) is the latest in a well established tradition of studying leptoproduction from the annihilation of a quark and anti-quark, known as the Drell-Yan process. The broad goal of E906/SeaQuest is measuring various properties of nucleon structure in order to learn more about quarks and Quantum Chromodynamics, the mathematical description of the strong force. The present work investigated violations of the Lam-Tung relation between virtual photon polarization and quark and lepton angular momentum. The violation of Lam-Tung can be explained as the signature of quark-nucleon spin-orbit coupling through the use of the Transverse-Momentum-Dependent (TMD) framework, which assumes that the initial transverse momentum of quarks is smaller than the hard scattering scale, but also non-negligible.;An analysis of the angular moments in Drell-Yan collected by E906/SeaQuest was performed with four different configurations in order to estimate the systematic errors attributed to each correction. After correction for background and error propagation,the final extraction of the azimuthal moment excluding contributions from the trigger was nu = 0.151 +/- 0.88(stat. ) +/- 0.346(syst.) at an average transverse momentum of 0.87 +/- 0.50 GeV/c and an average dimuon mass of 5.48 +/- 0.70 GeV. In the future, the magnitude of the systematic errors on the extraction could potentially be reduced by improving the quality of the trigger efficiency calculation, improving the intensity dependent event reconstruction efficiency, considering the changes in acceptance due to a beam shift relative to the E906/SeaQuest spectrometer, and improving the modeling of background.