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Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region

Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region. 2005. September 30, 2006 RHIC Spin Collaboration Meeting RIKEN, Wako, Japan K. Oleg Eyser University of California, Riverside. recoil. scattered. Jet Polarimeter Setup. 96 silicon strips: 6 x 2 x 8

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Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region

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  1. Absolute Polarization Measurementat RHIC in theCoulomb Nuclear Interference Region 2005 September 30, 2006RHIC Spin Collaboration MeetingRIKEN, Wako, Japan K. Oleg Eyser University of California, Riverside

  2. recoil scattered Jet Polarimeter Setup 96 silicon strips: 6 x 2 x 8 geometry reflects kinematics in: 5 cm displacement of beams 8 cm y ~ 80 cm x jet

  3. ADC (a.u.) TDC (a.u.) Recoil Protons a typical waveform single strip (example) tTOF (ns) recoil protonsfrom elastic scattering TDC¼ rise time scale 1.19 ns T0 calibration from proton signals TR (MeV) ADC(peak or integral) CalibrationAm (5.486 MeV)Gd (3.183 MeV) prompt events(large yield, filtered)

  4. 1 2 3 4 5 6 Beamgas backgroundfrom empty target runs: 2.4% - 3.4% elastic signal 1.0 < TR < 1.5 MeV 1.5 < TR < 2.0 MeV 2.0 < TR < 2.5 MeV 2.5 < TR < 3.0 MeV 3.0 < TR < 3.5 MeV strips 0 - 95 strips 0 - 95

  5. abort gaps(example: blue 120 bunch mode) 1.0 - 1.5 MeV bunch distributions, including all cutsblue and yellow detector sides separated 1.5 – 2.0 MeV 2.0 – 2.5 MeV 2.5– 3.0 MeV yellow abort gap blue abort gap 3.0 – 3.5 MeV 3.5– 4.0 MeV

  6. TargetYellow beamBlue beam Asymmetries and Polarization

  7. bunch shuffling yellow beam centered 120 bunch mode 5000 shuffles asymmetry ratio (beam / target)divided by its statistical error fit gaussian • too large where statistical errors are small • include systematic errors from abort gaps !!! • consistent with 1 within accuracy of number of filled bunches

  8. variations of proton signal regions beam and target asymmetries pick up more background, ratio (polarization) is very stable 1 strip 2 strips 3 strips 4 strips 5 strips all strips

  9. Systematic Error Summary simple asymmetries: left-right, up-down relative luminosity:no monitoruse integrated left-right yields cut dependence acceptance asymmetry:detector alignment efficiency asymmetry:detector efficiency yields include (s)ignal and (b)ackground Background should have noeffect at all on the determinationof the beam polarization !!!Issues when dealing with physicalproperties (analyzing power). if not polarization dependent !!! background yield 5% to 7%. (same for physics quantities)systematic errors of beam polarization smaller than 2%.(strip signal region variations, previous slide)

  10. 120 bunch mode TargetYellow beamBlue beam Beam Polarizations 120 bunch mode TargetYellow beamBlue beam

  11. Polarizations: comparison toonline numbers from Carbon polarimeters  one sigma bands pC online meas. both beams on jet(60 bunch mode) yellow beam on jet(60 & 120 bunch modes) blue beam on jet(60 & 120 bunch modes) 205 GeV/c blue measurements yellow measurements

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