Experiment 1039 at Fermi National Accelerator Laboratory

Experiment 1039 at Fermi National Accelerator Laboratory is poised to better understand the contribution of the sea quarks to the nucleon spin and is the successor to Experiment 906/SeaQuest. E1039 will utilize a 120 GeV proton beam, the mass spectrometer previously used in SeaQuest, and a transversely polarized target to have spin-dependent collisions. It has been known that the valence quarks contribute ~30% to the proton spin while the contribution of the gluons is still being studied. The main focus of E1039 will be to measure the Sivers function, which is a correlation between transverse spin of the sea quarks and nucleon spin, through the Drell-Yan process. Measurement of a non-zero quark Sivers function implies a dependence on quark orbital angular momentum for nucleon spin. A direct measurement of the Sivers function will provide further the efforts in solving the proton spin crisis by determining if there is a non-zero contribution of the sea quarks to the nucleon spin.