References - Bogoliubov Laboratory of Theoretical Physics - JINR

PROTON BEAM POLARIZATION MEASUREMENTS AT RHIC
A. Bazilevsky 1 , I. Alekseev 2 , E. Aschenauer 1 ,G.Atoyan 1 ,A.Bravar 3 ,G.Bunce 1 ,
G. Boyle 4 ,C.M.Camacho 5 , V. Dharmawardane 6 , R. Gill 1 , H. Huang 1 ,S.Lee 7 ,X.Li 8 ,
H. Liu 6 ,Y.Makdisi 1 , B. Morozov 1 , I. Nakagawa 4,9 ,H.Okada 1 ,D.Svirida 2 ,
M. Sivertz 1 and A. Zelenski 1
(1) Brookhaven National Laboratory, Upton, NY 11973, USA
(2) Institute for Theoretical and Experimental Physics (ITEP), 117259 Moscow, Russia
(3) University of Geneva, 1205 Geneva, Switzerland
(4) RIKEN-BNL Research Center, Upton, NY 11973, USA
(5) Los Alamos National Laboratory, Los Alamos, NM 87545, USA
(6) New Mexico State University, Las Cruces, NM 88003, USA
(7) Stony Brook University, SUNY, Stony Brook, NY 11794, USA
(8) Shandong University, China
(9) RIKEN, 2-1 Hirosawa Wako, Saitama 351-0198, Japan
Abstract
We discuss the beam polarization measurement strategy at RHIC with achieved
relative precision of better than 5%.
1 Introduction
Polarimetry is one of the crucial part of the RHIC Spin Program [1]. It provides precise
measurements of beam polarizations which is a necessary component of all high precision
spin dependent measurements at RHIC.
Two types of polarimeters are used at RHIC, which are based on small angle elastic
scattering, with sensitivity to the proton beam polarization coming from interference
between electromagnetic and hadronic amplitudes (Coulomb-Nuclear Interference (CNI)
region).
One type of polarimeter (pC) uses an ultra-thin (10–20 μg/cm 2 ) carbon ribbon target,
and provides fast relative polarization measurements with a few percent statistical
uncertainty in 20–30 sec. The other type polarimeter (H-Jet) uses a polarized hydrogen
gas target and utilizes the analyzing power in proton-proton elastic scattering in the
CNI region. It accumulates data over the entire store and provides absolute polarization
measurements, with ∼10% statistical uncertainty in a store (6–8 hours). H-Jet data accumulated
over several stores are used for the absolute calibration of the pC polarimeters.
In addition, two experiments STAR and PHENIX employ local polarimeters which
are used to set up and to monitor the spin direction at collision. They also proved to be
a valuable tool for beam polarization monitoring when spin orientation at collision was
set up to be transverse.
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