First measurement of AN at s=200GeV in polarized proton-proton elastic scattering at RHIC

We report on the first measurement of the single spin analyzing power (AN) at s=200GeV, obtained by the PP2PP experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured in the four momentum transfer t range 0.01⩽|t|⩽0.03(GeV/c)2. Our result, averaged over the whole |t| interval is about one standard deviation above the calculation, which uses interference between electromagnetic spin-flip amplitude and hadronic non-flip amplitude, the source of AN. The difference could be explained by an additional contribution of a hadronic spin-flip amplitude to AN.