Measurement Of Continuum Dimuon Production In 800-GeV/C Proton-Nucleon Collisions

Fermilab Experiment 866 has performed an absolute measurement of continuum dimuon (Drell-Yan) cross sections in 800-GeV/c $pp$ and $pd$ interactions. Results differential in the mass, Feynman-$x$ ($x_F$) and transverse momenta ($p_T$) of the dimuon pairs are reported. These results represent the most extensive study of the Drell-Yan process to date, based on a data sample of 175,000 dimuon events covering the widest range in kinematics yet achieved ($4.2 \leq M \leq 16.85$ GeV and $-0.05 \leq x_F \leq 0.8$) with this level of precision. The cross sections are primarily sensitive to the magnitude and shape of the light antiquark distributions ($\bar{d}(x)$ and $\bar{u}(x)$) in the nucleon, but also provide important information on the valence quarks as well as the gluons. They are in good agreement with other existing proton-induced Drell-Yan experiments. There is also general agreement between the data and next-to-leading-order calculations based on various sets of parton distribution functions. Differences between data and theory are examined, and the potential impact of these data on future parameterizations of the parton distributions are discussed.