Transverse Single Spin Asymmetry of π0 and η Mesons at RHIC/PHENIX

We presented measurements of the transverse single spin asymmetries ([Formula: see text]) for neutral [Formula: see text] and [Formula: see text] meson at forward rapidities and central rapidity with the PHENIX detector at RHIC at 62.4 GeV and 200 GeV. At mid-rapidity, [Formula: see text] and [Formula: see text] are reconstructed from di-photon decay. At forward rapidities, [Formula: see text] and [Formula: see text] meson are measured using di-photons decays and electromagnetic clusters due to the photon merging effects are significant for energy [Formula: see text]. The neutral-pion measurement of [Formula: see text] at mid-rapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, both neutral [Formula: see text] and [Formula: see text] [Formula: see text] exhibit sizable asymmetries. The origin of the forward [Formula: see text] is presently not understood quantitatively. We also measured [Formula: see text] meson cross section for [Formula: see text] GeV/c and [Formula: see text]. It is well described by a NLO pQCD calculation.