1. Polarization Measurement of 100GeV Proton Beams at RHIC with CNI pC Polarimeter Itaru Nakagawa (RIKEN/RBRC) On behalf of CNI Polarimeter Group I.G.Alekseev A A.Bravar B G.Bunce B S.Dhawan D R.Gill B H.Huang B W.Haeberli E G.Igo F O.Jinnouchi V.P.Kanavets A K.Kurita H A.Khodinov J Z.Li B Y.Makdisi B A.Nass B W.Lozowski I W.W.MacKay B H.Okada G S.Rescia B T.Roser B N. Saito G H.Spinka L D.N.Svirida A D.Underwood L C.Witten F T.Wise I J.Wood F A.Zelenski B RBRC ITEP A BNL B ANL C Yale U D Wisconsin U E UCLA F Kyoto U G Rikkyo U H Indiana U I StonyBrook U J IUCF K Argonne U L Itaru Nakagawa (RIKEN/RBRC) On behalf of CNI Polarimeter Group I.G.Alekseev A A.Bravar B G.Bunce B S.Dhawan D R.Gill B H.Huang B W.Haeberli E G.Igo F O.Jinnouchi V.P.Kanavets A K.Kurita H A.Khodinov J Z.Li B Y.Makdisi B A.Nass B W.Lozowski I W.W.MacKay B H.Okada G S.Rescia B T.Roser B N. Saito G H.Spinka L D.N.Svirida A D.Underwood L C.Witten F T.Wise I J.Wood F A.Zelenski B RBRC ITEP A BNL B ANL C Yale U D Wisconsin U E UCLA F Kyoto U G Rikkyo U H Indiana U I StonyBrook U J IUCF K Argonne U L

2. Polarimetry: Impact on RHIC-SPIN Physics Asymmetries Single Spin Asymmetries Double Spin Asymmetries Polarization measurement by Elastic pp/pC Polarized proton Recoil carbon 90º in Lab frame Carbon target P beam Required Accuracy ~5%

3. A N at Coulomb Nuclear Interference (CNI) Region ? Pomeron exchange zero hadronic spin-flip With hadronic spin-flip (E950) Phys.Rev.Lett.,89,052302(2002) pC Analyzing Power Requires absolute calibration p = 21.7GeV Need to measure A N pC @ 100GeV Elastic pp ( High energy & small t limit )

4. Characteristics of pC polarimeter Large Cross Section Solid target 20 sec./measurement with  (sta) ~ 2% Immediate feedback to accelerator operation “Fill by Fill” & “Bunch by Bunch” measurement Polarization profile measurement A N pC ~ a few %  High Event Rate

5. RHIC Polarimetry

6. pC Detector Setup Ultra thin Carbon ribbon Target (3.5  g/cm 2 )1 3 4 5 6 2 Si strip detectors (TOF, E C ) 15cm 10mm 2mm pitch 12 strips p + implants ~150 nm depth 72 strips in total Thin dead layer for low energy carbon spectroscopy ~100mV Bunch Next Bunch (60 bunch mode) Shaped Si Signal Next Bunch (120 bunch mode) Wave Form Digitizer (WFD) 420 Msamples/sec - Pulse Height - Bunch ID - TOF - Integral (Q) - TMAX - revolution # Select carbons at on-board LUT Scaler data Scaler data Asymmetry calculation Asymmetry calculation Online results (to experiments) Online results (to experiments) Event by event data Stored in on-board memory Stored in on-board memory Used for offline detailed study Used for offline detailed study offline online Redundancy  Systematic/Consistency Check

7. Event Selection +3  -3  12 C  Run4 Run5

8. Run05 Online Results PHENIX Physics Store Fill Number Polarization [%]

9. Run5 Polarization Profile 2mm Polarization Count Rate[Hz]

10. pC extended t-range A N @ 100GeV No Hadronic Spin flip Best Fit with Hadronic Spin-flip hep-ph/0305085 From Run4 pp A N pC @100GeV will soon be finalized > 0.1(GeV/c) 2 Run5 Data from Run4 Preliminary

11. Summary RHIC Beam Polarization was measured by taking asymmetry of pC elastic scattering. Absolute calibration was done using P beam determined by elastic pp scattering data(Run4). A N pC was measured for extended t range (Up to t>0.1 (GeV/c) 2 )to explore t-evolution of hadronic spin-flip amplitude. RHIC Beam Polarization was measured by taking asymmetry of pC elastic scattering. Absolute calibration was done using P beam determined by elastic pp scattering data(Run4). A N pC was measured for extended t range (Up to t>0.1 (GeV/c) 2 )to explore t-evolution of hadronic spin-flip amplitude.