Measurements of the energy dependence of the analyzing power in pp elastic scattering in the CNI region

Abstract

We present new measurements of the analyzing power AN in proton-proton elastic scattering in the Coulomb-Nuclear Interference region at √s = 7.7 and 21.7 GeV obtained with the polarized atomic hydrogen jet target at RHIC. These measurements complement our earlier results at √s = 6.8 and 13.7 GeV confirming the presence of a hadronic helicity flip amplitude contribution in proton-proton elastic scattering at lower energies (√s <8 GeV), while higher energy data (√s >13 GeV) are consistent with no hadronic helicity flip contribution.