Spin Dependence in Polarized pC → pC Scattering at Low Momentum Transfer and Polarimetry at RHIC

Status of the RHIC Spin Program

“…The observed −t dependence of the measured spin-dependent asymmetry, P beam × A N , suggests substantial contributions from the hadronic spin flip amplitude, meaning that independent measurements are necessary to determine the beam polarization (P beam ). Precision measurements were made for the first time at 100 GeV in RHIC run 4 (April through May, 2004) by exploiting identical particle symmetries in polarized proton elastic scattering from a polarized gas jet target [7,8]. The contribution of the spin dependendent strong interaction amplitude to small |t| elastic scattering is of interest in its own right, and can be extracted from spin observables measured at RHIC in either fixed target experiments with the polarized gas jet target or with carbon ribbon targets, or by studying elastic scattering of the polarized colliding beams [9], which is the object of the pp2pp experiment at RHIC.…”