The Beam-Beam Counter: A Local Polarimeter at STAR

At the Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider (RHIC) the Beam-Beam Counter (BBC) array for the Solenodial Tracker at RHIC (STAR) is a very versatile tool for polarized proton beam diagnostics. The BBC setup provides an excellent minimum bias trigger; and for hits on the...

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Bibliographic Details
Published in:AIP conference proceedings 2008, Vol.980 (1), p.390-396
Main Author: Whitten Jr, C A
Format: Article
Language:English
Subjects:
ALGORITHMS
ASYMMETRY
BROOKHAVEN RHIC
GEV RANGE
NUCLEAR PHYSICS AND RADIATION PHYSICS
POLARIMETERS
POLARIMETRY
POLARIZATION
POLARIZATION-ASYMMETRY RATIO
POLARIZED BEAMS
PROTON BEAMS
PROTONS
SCINTILLATION COUNTERS
SPIN
TIME DEPENDENCE
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Summary:At the Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider (RHIC) the Beam-Beam Counter (BBC) array for the Solenodial Tracker at RHIC (STAR) is a very versatile tool for polarized proton beam diagnostics. The BBC setup provides an excellent minimum bias trigger; and for hits on the inner annuli of six hexagonal scintillator tiles the BBC coincidence trigger with a suitable algorithm has a quite large single spin analyzing power ~8X10-3 for 100 GeV polarized proton -100 GeV polarized proton collisions. The STAR BBC is a very effective local polarimeter at these energies. For 100 GeV 'p-vector '-100 GeV 'p-vector ' running in 2006 the BBC measured single spin asymmetries to a statistical accuracy of better than 2% for a data run of 20-30 minutes; and these measurements were quite robust. For fills with a duration of at least six hours these STAR BBC asymmetry measurements were used to study the time dependence of the polarization for 100 GeV proton beams in the RHIC rings. The decrease of the polarization is quite small, < 0.01PB per hour.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.2888113