Abstract. Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of A&am/Pbeam < 5%.The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power AN of this process has allowed us to achieve Mbeam/Pbeam = 4.2% in 2005 for the first long spin-physics run.In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004 -2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c)2) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.
Precise measurements of the single spin asymmetry, A N and the double spin asymmetry, A NN , 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 RHIC polarized proton beam at 24 GeV/c and 100 GeV/c. The polarized gaseous proton target allowed us to achieve the measurement of A NN in the CNI region for the first time. Our results of A N and A NN provide significant constraints to determine the magnitude of poorly known hadronic single and double spin-flip amplitudes at this energy.
Abstract. The polarization measurement through elastic @C) reaction plays a crucial role in the polarized proton beam operation of Relativistic Heavy Ion collider at Brookhaven National Laboratory. As well as measuring the polarization, the unknown analyzing power AN of elastic @,C) is determined as well in combination with the absolute polarization meausement by a Hjet polarimeter. The systematic uncertainty of the Run05 measurements are discussed as well as introducing the experimental apparatus of the polarimeter system.
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