A current scan was made for the Yellow and Blue beam spin rotators at STAR during fill 15425 (April 8-9, 2011) in preparation for longitudinal running.  Five combinations of current settings were used.  STAR collected 3 ZDC polarimetry runs for each of these combinations.

The attachments give the settings and realtime results from the scaler-based analysis.  The analysis based on trigger-data shows consistent results, but with a factor 10 less precision (100 times less data recorded).

CNI polarimeter measurements were made before and after the scan.  However, the CNI results for both beams and with both polarimeters should still be copied from the eLog.  Our shiftlog entries show that the polarizations were typical and at the level of 40-45%.

Following the scan, an optimal set of currents was applied and 3 additional ZDC polarimetry runs were taken (12099014-16). The online results indicate that the residual transverse components are at the level of 5% for the Yellow beam and at the level of 2% for the Blue beam.  No evidence for systematics larger in size than the statistical uncertainties was found from the ZDC polarimetry measurements at negative xF.

Thanks to the crews of the evening and night shift at STAR and MCR, and in particular Haixin Huang and Vahid Ranjbar.

Oleksandr Grebenyuk / Ernst Sichtermann