Abstract
We present a measurement of the transverse single-spin asymmetry for π0 and η mesons in p↑+p collisions in the pseudorapidity range |η|<0.35 and at a center-of-mass energy of 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. In comparison with previous measurements in this kinematic region, these results have factor-of-3-smaller uncertainties. As hadrons, π0 and η mesons are sensitive to both initial- and final-state nonperturbative effects for a mix of parton flavors. Comparisons of the differences in their transverse single-spin asymmetries have the potential to disentangle the possible effects of strangeness, isospin, or mass. These results can constrain the twist-3 trigluon collinear correlation function as well as the gluon Sivers function.