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Polarization Measurement of 100GeV Proton Beams at RHIC with CNI pC Polarimeter

This study presents the measurement of 100GeV proton beam polarization at RHIC using the Coulomb Nuclear Interference (CNI) pC polarimeter. The impact of polarimetry on RHIC-SPIN single spin asymmetries and double spin asymmetries is evaluated, and the characteristics of the pC polarimeter are discussed.

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Polarization Measurement of 100GeV Proton Beams at RHIC with CNI pC Polarimeter

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  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.AlekseevA A.BravarB G.BunceB S.DhawanD R.GillB H.HuangB W.HaeberliE G.IgoF O.Jinnouchi V.P.KanavetsA K.KuritaH A.KhodinovJ Z.LiB Y.MakdisiB A.NassB W.LozowskiI W.W.MacKayB H.OkadaG S.ResciaB T.RoserB N. SaitoG H.SpinkaL D.N.SviridaA D.UnderwoodL C.WittenF T.WiseI J.WoodF A.ZelenskiB RBRC ITEPA BNLB ANLC Yale UD Wisconsin UE UCLAF Kyoto UG Rikkyo UH Indiana UI StonyBrook UJ IUCFK Argonne UL

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

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

  4. Characteristics of pC polarimeter  High Event Rate • 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 • ANpC ~ a few %

  5. Absolute Polarimeter (H jet) RHIC pC Polarimeters Siberian Snakes BRAHMS & PP2PP (p) RHIC PHENIX (p) STAR (p) Siberian Snakes Spin Rotators Solenoid Snake LINAC BOOSTER Pol. Proton Source 500 mA, 300 ms AGS Warm Snake 200 MeV Polarimeter AC Dipole AGS pC CNI Polarimeter Cold Snake RHIC Polarimetry

  6. Ultra thin Carbon ribbon Target (3.5mg/cm2) 6 1 15cm 2 5 Si strip detectors (TOF, EC) 3 4 pC Detector Setup ~100mV Shaped Si Signal Next Bunch (60 bunch mode) Next Bunch (120 bunch mode) Bunch Wave Form Digitizer (WFD) Thin dead layer for low energy carbon spectroscopy • 420 Msamples/sec • - Pulse Height - Bunch ID • TOF - Integral (Q) • TMAX - revolution # 2mm pitch 12 strips 10mm p+ implants ~150 nm depth online • Select carbons at on-board LUT • Scaler data • Asymmetry calculation • Online results (to experiments) 72 strips in total Redundancy  Systematic/Consistency Check offline • Event by event data • Stored in on-board memory • Used for offline detailed study

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

  8. Run05 Online Results Polarization [%] Polarization [%] PHENIXPhysics Store Fill Number Fill Number Polarization [%] Stable Measurement

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

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

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

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