Measurements of single and double spin asymmetry in pp elastic scattering in the CNI region with a polarized atomic hydrogen gas jet target

Precise measurements of the single spin asymmetry AN, and the double spin asymmetry ANN, in proton-proton (pp) elastic scattering in the region of four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c)(2) have been performed using a polarized atomic hydrogen gas jet target and the Relativistic Heavy Ion Collider (RHIC) polarized proton beam. We present measurements of A(N) and A(NN) at center-of-mass energies root s = 6.8 and 13.7 GeV. These spin-dependent observables are sensitive to the poorly known hadronic spin-dependent amplitudes. Comparing A(N) at different energies, a root s dependence of the hadronic single spin-flip amplitude is suggested. A hadronic double spin-flip amplitude from the A(NN) data is consistent with zero within a 2-sigma level. We also present Delta(sigma T), estimated from the measured A(NN) data. The results for Delta(sigma T) are consistent with zero. Our results provide significant constraints toward a comprehensive understanding of the reaction mechanism for pp elastic scattering.