Extracting the proton ū content from pp → direct photon plus jet cross sections

An analysis procedure is proposed to measure the antiquark distributions in the proton over the region 0.01<x<0.1. The procedure involves the measurement of high p_t asymmetric direct photon and jet final states in pp interactions. This measurement can be made at the BNL RHIC collider running in pp mode at an energy of √s = 500 GeV/c. This analysis identifies a region of phase space where the contribution from quark-antiquark annihilation uncharacteristically approaches the magnitude of the contribution from the leading process, quark-gluon Compton scattering. The forward-backward angular asymmetry in the parton center of mass is sensitive to the antiquark content of the proton and the ū parton density function can be extracted.