Measurement of Direct Photon Cross Section and Double Helicity Asymmetry at √s = 510 GeV in pp Collisions at PHENIX

Understanding the gluon spin contribution to the proton spin is important to solving the proton spin puzzle. Direct photon production in the longitudinally polarized proton (pp) collisions provides a "clean" probe to the gluon spin at leading order. Compared with hadron production, there is little fragmentation involved in direct photon production. The Relativistic Heavy Ion Collider (RHIC) is the only collider that is capable of producing two longitudinal polarized proton beams. The RHIC run of the year 2013 provides the largest integrated luminosity (155 pb^-1) in pp collisions. The Electromagnetic Calorimeter at PHENIX has fine granularity to identify the π⁰ background up to transverse momentum p_T of 30 GeV/c. In this talk, I will present the direct photon cross section and double helicity asymmetry (A_LL) for photon p_T of 6--30 GeV/c and 6--20 GeV/c, respectively. When included in future global analyses, our results will provide an independent constraint on the gluon spin contribution to the proton spin.