Drell-Yan Studies at Fermilab

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It is now a well-established fact that nucleons, protons and neutrons, are made up of more elementary particles called quarks. The main physics program supported by this award is directed at the study of the quark structure of nucleons and the nuclei that are made up of these nucleons. Research will be carried out at the Fermilab Laboratory near Chicago as part of a collaboration called SeaQuest. This collaboration is focused on the production of pairs of particles called muons, which are like electrons but more massive, used as a probe of the anti-quark distributions in the nucleon (and whether these distributions are modified in nuclei). This information will provide direct input to theoretical models of the proton, and shed light on the origin of the proton's spin. A related study, using a polarized proton beam, will provide new information on symmetries of the quark distributions based on predictions from the fundamental theory of Quantum Chromodynamics. In addition, the Michigan group will lead the operation of the low-temperature hydrogen targets at the SeaQuest experiment, and participate in the development of a polarized hydrogen target for a next-generation experiment. Education and training of both undergraduate and graduate students, as well as outreach aimed at the general public, is an important aspect of this research program. The SeaQuest experiment at the Fermilab Laboratory near Chicago will provide a better understanding how light anti-quarks are distributed in nucleons and nuclei, on the physical mechanism that generates the sea of the nucleon, and how orbital angular momentum might contribute to the nucleon spin. A smaller, but very important effort will be spent on developing a polarized Drell-Yan program at Fermilab that is complementary to the spin physics programs at Brookhaven National Lab and Jefferson Lab. This program builds on the expertise the group has gained, and is a natural extension of the group's work over the past years. It allows them to play a major role in the Drell-Yan experiment at Fermilab now, and to lead the way towards a polarized Drell-Yan program at Fermilab in the future.