Single spin asymmetry AN in polarized proton-proton elastic scattering at s=200GeV

We report a high precision measurement of the transverse single spin asymmetry AN at the center of mass energy s=200GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The AN was measured in the four-momentum transfer squared t range 0.003⩽|t|⩽0.035(GeV/c)2, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of AN and its t-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this s, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.