p-Carbon polarimetry at RHIC. Page: 3 of 12
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p-Carbon Polarimetry at RHIC
I. Nakagawa*,t, I. Alekseev**, A. Bazilevskyt, A. BravarO, G. Buncett,
S. Dhawan, K.O. Eyserl, R. Gill+, W. Haeberlitt, H. Huang+, Y. Makdisi+,
A. Nassit, H. Okada+, E. Stephenson"e, D.N. Svirida**, T. Wisett, J. Wood+
and A. Zelenski+
*RIKEN, 2-1 Hirosawa Wako, Saitama 351-0198, Japan
tRIKEN-BNL Research Center Upton, NY 11973, USA
**Institute for Theoretical and Experimental Physics (ITEP), 117259 Moscow, Russia
lBrookhaven National Laboratory, Upton, NY 11973, USA
University of Geneva, 1205 Geneva, Switzerland
IYale University, New Haven, CT 06520, USA
"IUniversity of California, Riverside, CA 92521, USA
tt University of Wisconsin, WI 53706, USA
$$ University of Erlangen, 91058 Erlangen, Germany
Indiana University Cyclotron Facility, Bloomington, IN 47408, USA
Abstract. The polarization measurement through elastic (p,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
(p,C) is determined as well in combination with the absolute polarization meausement by a H-
jet polarimeter. The systematic uncertainty of the RunO5 measurements are discussed as well as
introducing the experimental apparatus of the polarimeter system.
Keywords: polarimeter, CNI, elastic scattering, polarized proton beam
The polarization of the proton beams at the Relativistic Heavy Ion Collider (RHIC)
is measured using both a hydrogen jet (H-Jet) [1, 2] and carbon polarimeters[3, 5].
These polarimeters are set up in the 12 o'clock area in the RHIC ring. The H-Jet
polarimeter is located at the collision point allowing measurements of both beams. Two
identical pC-polarimeters are equipped in the yellow and blue rings, where the rings are
separated. The pC-polarimeter measures relative polarization to a few percent statistical
accuracy within 20 to 30 seconds using an ultra-thin (typically 10 - 20 yg/cm2) carbon
ribbon target, providing fast feedback to beam operations and experiments. The absolute
normalization is provided by the H-Jet polarimeter, which measures over 1 ~ 2 days
to obtain ~ 5% statistical uncertainty (in RunO5). Thus, the operation of the carbon
polarimeters was focused on better control of relative stability between one measurement
to another measurement rather than measuring the absolute polarization.
The published data of the analyzing power for the elastic polarized proton-carbon
scattering is available up to the 21.7 GeV/c. There are no published data available
at the storage (flat-top) proton beam energy of 100 GeV where the colliding experi-
ment was performed in RHIC. Shown in the Fig. 1 is the analyzing power measured
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Nakagawa,I.; Makdisi,Y.; Alekseev, I.; Bazilesky, A.; Bravar, A.; Bunce, G. et al. p-Carbon polarimetry at RHIC., article, September 10, 2007; United States. (digital.library.unt.edu/ark:/67531/metadc901626/m1/3/: accessed July 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.