Transverse Single-Spin Asymmetries of Midrapidity Direct Photons and Neutral Mesons at PHENIX

Abstract

Results are presented for the transverse single-spin asymmetries of direct photons, neutral pions, and eta mesons for |\eta|<0.35|η|<0.35 from p^\uparrow + pp↑+p collisions with \sqrt{s} = 200s=200 GeV at PHENIX. As hadrons, \pi^0π0 and \etaη mesons are sensitive to both initial- and final-state effects and at midrapidity probe the dynamics of gluons along with a mix of quark flavors. Because direct photon production does not include hadronization, the direct photon TSSA is only sensitive to initial-state effects and at midrapidity provides a clean probe of the gluon dynamics in transversely polarized protons. All three of these results will help constrain the collinear twist-3 trigluon correlation function as well as the gluon Sivers function, improving our knowledge of spin-dependent gluon dynamics in QCD.