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Polarization Profile and its impact on polarization measurements

Polarization Profile and its impact on polarization measurements. A.Bazilevsky For the RHIC Polarimetry group RSC meeting March 21, 2007. Polarization vs Luminosity Profile, Blue. Polarization vs Luminosity Profile, Yellow. Polarization Profile Impacts.

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Polarization Profile and its impact on polarization measurements

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  1. Polarization Profile and its impact on polarization measurements A.Bazilevsky For the RHIC Polarimetry group RSC meeting March 21, 2007

  2. Polarization vs Luminosity Profile, Blue

  3. Polarization vs Luminosity Profile, Yellow

  4. Polarization Profile Impacts • We do see polarization profile (in yellow beam) • Polarization measurements depend on target position (need correction?) • Normalization to jet polarimeter measurements requires correction (jet pol. measures luminosity averaged value) • Polarization values for experiments requires correction (experiments “utilize” luminosity averaged value) • We have only few measurements of profiles • Do they represent the whole set of Run5 data? Probably not • Are there other ways to estimate the average polarization profile and its variation?

  5. Polarization vs Rate P Polarization+Luminosity profiles  Polarization vs Rate dependence If both profiles are gaussians: L

  6. Polarization vs Rate, yellow Pol Rate Pol • Rate normalized for beam intensity (WCM) • Variation in rate are due to luminosity profile, beam emittance fluct. etc. • Variation in polarization are due to variation in polarization at injection and shower profile Rate

  7. Polarization vs Rate, blue Pol Rate Pol • Rate normalized for beam intensity (WCM) • Variation in rate are due to luminosity profile, beam emittance fluct. etc. • Variation in polarization are due to variation in polarization at injection and shower profile Rate

  8. Pol. Profile fit Pol For each slice in Rate we can get Pol distribution, define <Pol> and its uncertainty (stat. errors do not matter if they are much smaller than variation in Pol) Then define the average polarization profile and its uncertainty from the fit Rate We didn’t take into account variation in Rate (~20% in yellow). Does it matter? – Yes The effect is obtained from simple MC and included in syst. errors Measurement points are not uniformly distributed, the fit result may vary with binning – assigned additional error L/ P = 0.38  0.04(stat)  0.04(model)  0.02(bin) L/ P = 0.00 + 0.09(stat)

  9. Variation in Pol. profile Pol • Pol. variation in each slice in Rate includes: • Intrinsic variation in polarization • Variation in polarization profile (relative to lum. profile) • Bin width + pol. profile • Rate variation + pol. Profile • From simultaneous fit of Pol. distributions in all slices we obtain • Intrinsic variation in polarization • Variation in polarization profile (relative to lum. profile) Rate (L/ P) = 0.20  0.50 (L/ P) = 0.00  0.25

  10. Implication to jet normalization Jet polarimeter measures lum. average profile pC integrates only in one direction (usually in Y) This correction: L/ P = 0.38  0.07  C=0.930.02 L/ P = 0.38  0.07  C=1.000-0.005 If want to apply correction fill-by-fill (L/ P) = 0.20  0.50  C= 0.930.05 (L/ P) = 0.00  0.25  C=1.00 - 0.03

  11. BackupComparison to profile measurements Pol Green: real measurements of pol. profiles Black-solid: average profile from fit Black-dashed:1 variation of pol. Profile from fit Rate Pol Rate

  12. Backupsimultaneous fit Rate=0.2-0.4 Rate=0.4-0.6 Rate=0.6-0.8 Rate=0.8-1.0 2/NDF=13/17 Pol 2/NDF=17/12 Pol

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