K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -1- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region K. Oleg Eyser University of California, Riverside SPIN th International Spin Physics Symposium Kyoto, Japan October 2, 2006

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -2- Polarized Protons in RHIC this talk: normalization with the Jet Polarimeter TANSTAAFL !!! (x) two Carbon polarimeters plus one Jet polarimeter fast measurements (30 seconds) with fiber targets needs normalization normalization with polarized gas jet target slow (several days) measurement (x) R. Heinlein

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -3- Polarization Measurement scattered recoil left right Rabi spectrometer: hydrogen hyperfine structure Elastic scattering: proton-proton, proton-Carbon, etc. W/W 0 B/B C

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -4- The Jet Polarimeter x y jet 96 silicon strips: (6 x 2 x 8) geometry reflects kinematics of elastic pp scattering displacement of beams ~ 80 cm 8 cm 5 cm

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -5- DAQ and Calibration T R (MeV) t TOF (ns) prompt events (large yield, filtered) ADC peak or integral calibration Am (5.486 MeV) Gd (3.183 MeV) TDC ¼ rise time scale 1.19 ns recoil protons from elastic scattering TDC (a.u.) ADC (a.u.) FPGA onboard memory DAQ PC a typical waveform single strip example

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -6- Proton Identification T R (MeV) t TOF (ns) t TDC (ns) t 0 (ns) single strip example

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -7- Asymmetry Measurement (dashed) scaled with target polarization: 96% atomic / 92% effective scaled with asymmetry ratio: beam / target (1 MeV – 4 MeV) (solid) formal description in terms of helicity amplitudes T R (MeV)

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -8- Background Contributions I yield (polarization up / down) 1.0 – 1.5 MeV beamgas background: empty target runs normalized with beam intensities background yield: between 2.4% and 3.4% about 0.3 to 0.5 of total background no polarization dependence

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -9- Background Contributions II abort gap 2abort gap 1 bunch number prompt background contribution from displaced beam in signal region gap 2gap 1 abort gaps: prompt background contribution from displaced beam kinematics: no elastic proton signal background yields: between 1.2 % and 5.0 %

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -10- Systematic Errors determination of beam polarization: simple asymmetries: for cross checks (creates acceptance asymmetry)(creates luminosity asymmetry) (s)ignal and (b)ackground yields: background 5% - 7% not polarization dependent background contributes in second order to determination of beam polarization

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -11- Background Effects elastic pp scattering signal: two detector strips (out of eight) in each (of six) detector pads background roughly evenly distributed  4 x background asymmetries reflect an increase in background asymmetry ratio (beam polarization) is only weakly affected backgound yield < 7% systematic error ΔP < 2% two stripsfour stripseight strips target asymmetry beam asymmetry T R (MeV)

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -12- Polarization Measurements at RHIC goal: contains systematic errors of Jet and pC Polarizations of up to 49.4% have been measured at RHIC in Statistical errors are as small as 1.4%. An upper limit for systematic uncertainties of 2% has been determined. The total uncertainty for fast measurements is coming close to goal. Systematic studies of Jet and pC polarimeters are ongoing. Hadronic helicity amplitudes can be further determined from data sets. yellow beamPΔP stat period %2.9 % period %2.9 % period %1.4 % blue beamPΔP stat period %2.8 % period %3.8 % period %1.7 % normalization uncertainty for pC measurements

K.O. Eyser --- Absolute Polarization Measurement at RHIC in the Coulomb Nuclear Interference Region -13- Thank You! I. Alekseev, (1) A. Bravar, (2) G. Bunce, (2,3) S. Dhawan, (4) R. Gill, (2) W. Haeberli, (5) H. Huang, (2) Y. Makdisi, (2), I. Nakagawa, (6) A. Nass, (7) H. Okada, (6,8), E. Stephenson, (9) D. Svirida, (1) T. Wise, (5) J. Wood, (2) A. Zelenski (2) (1) ITEP (2) Brookhaven National Laboratory (3) RIKEN BNL Research Center (4) Yale University (5) University of Wisconsin, Madison (6) RIKEN (7) University of Erlangen (8) Kyoto University (9) Indiana University, Bloomington