pC polarimeter at RHIC. Status and performance.

1. S. Bravar, G. Bunce+, R. Gill, H. Huang, Y. Makdisi, A. Nass, A. Zelensky: Brookhaven National Laboratory, Upton, USA O. Jinnouchi: Riken-BNL Research Center, Upton, USA I. Nakagawa: RIKEN, Saitama, Japan I.G. Alekseev, V.P. Kanavets, D.N. Svirida: ITEP, Moscow, Russia S. Dhawan: Yale University, New Haven, USA W. Haeberli, T. Wise: University ofWisconsin, Madison, USA G. Igo, C. Whitten, J. Wood: UCLA, Los Angeles, USA K. Kurita: Rikkyo University, Tokyo, Japan A. Khodinov: SUNY, Stony Brook, USA H. Okada, N. Saito: Kyoto University, Kyoto, Japan W. Lozowski, E. Stephenson: IUCF, Bloomington, USA +also Riken-BNL Research Center pC polarimeter at RHIC. Status and performance. IX WORKSHOP ON HIGH ENERGY SPIN PHYSICS, Dubna, September 27 - October1, 2005

2. RHIC-Spin accelerator complex RHIC pC “CNI” polarimeters absolute pH polarimeter BRAHMS & PP2PP PHOBOS RHIC Siberian Snakes PHENIX STAR Siberian Snakes Spin Rotators 5% Snake Pol. Proton Source LINAC BOOSTER AGS 200 MeV polarimeter AGS quasi-elastic polarimeter 20% Snake AGS pC “CNI” polarimeter Rf Dipoles Igor Alekseev (ITEP)

3. Challenge • Absolute polarization measurement withDPbeam / Pbeam < 0.05 for experiments. • Fast (< 5 min) measurement for accelerator debugging. • Ramp and profile measurements. • Fast but relative pC-polarimeter; • Slow but absolute p-polarized H-jet polarimeter. • Road to the absolute polarization: A JET target polarization Ptarget(Breit-Rabi polarimeter) BAN for elastic pp in CNI region: AN = - 1 / PtargeteN’ CPbeam = 1 /ANeN” (B & C) can be combined in a single measurement: Pbeam/ Ptarget = - eN’ / eN” “self calibration” works for elastic scattering only DCALIBRATION: ANpC for pC CNI polarimeter in covered kinematical range: ANpC = 1 / PbeameN”’ (B & C & D) measured simultaneously with several insertions of carbon target E BEAM POLARIZATION:Pbeam = 1 / ANpCeN”” to experiments Igor Alekseev (ITEP)

4. Elastic scattering in the CNI region Pure CNI Regge poles /Pomeron exchange ANarises mainly from interference between EMspin-flip amplitude and hadronic non spin-flip amplitude(CNI = Coulomb – Nuclear Interference) AN is also sensitive probe to hadronic spin flip amplitude • All kinematics is defined by recoil particle. • For all RHIC beam energies recoil particle goes at 90o. • Analyzing power small, but with weak energy dependence. • Large cross section  very good figure of merit. • Need to collect 2-5107 events per measurement. • Energy of the recoil particle is very small  target must be extremely thin. M m,p TR  Igor Alekseev (ITEP)

5. pC polarimeter setup Ultra thin Carbon ribbon Target (3.5mg/cm2) 6 1 15cm 2 5 Si strip detectors (TOF, EC) 3 4 ~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 # No dead time ! 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 offline Event by event data • Stored in on-board memory • Used for offline detailed study Igor Alekseev (ITEP)

6. FPGA block diagram: V9 OR MUX ADC 3pt Filter Virtex FPGA Waveform FIFO / Delay Baseline Subtraction 140 MHz 1/4 Time CFD, TMAX Amplitude :2 Baseline Calculation ControlLogic Integral Result FIFO 70 MHz LevelTrigger Delim CAMAC readout Int/Ampl LUT Time/Ampl LUT Bunch #, Rev. # Bunch 0 SYNC and Window Logic AND Bunch Polarization Pattern +1 Ext INH Scalers&histograms Bunch # Distr. Energy P0 Distr. Special Scalers: P+,P–,P0, BG always accessible INH 2-dim T(E) Hist. Energy P+ Distr. Energy P– Distr. to Memory Igor Alekseev (ITEP)

7. FPGA algorithms baseline Pipeline (for each bunch crossing) AMAX/4 Baseline subtraction AMAX and tMAX Integral tMAX tCFD tCFD AMAX Use AMAX versus tCFD lookup table Fill internal histograms Move to memory FIFO • Baseline is averaged for about a dozen bunch crossings without signal. • No dead time processing and accepting events. • Nearly 2·108 events can be stored in the onboard memory for one measurement. Igor Alekseev (ITEP)

8. Improvements 2005 • New ceramic supports • USB 2.0 readout: up to 2 Mevents/second  all measurements are done now in event mode  all data are available for off-line analysis. • Independent BLUE and YELLOW DAQ hardware. • Better WFD time and amplitude reconstruction. NO BEAM CHARGE INDUCED SIGNAL !!! (Up to 2·1011 p/bunch) • Top secret: every second line IS GROUND the whole way down to the very strip • No pileup in the preamp • Lower limit in –t is only by the detector noise • No signal distortion • No upper limit on –t Igor Alekseev (ITEP)

9. Recoil particle identification (2004) carbon MC ~ 11.17 GeV sM ~ 1.5 GeV prompts alpha Invariant Mass Plots by O. Jinnouchi Igor Alekseev (ITEP)

10. pC: shape is different ! Rer5=0, Imr5=0 no hadron spin-flip Plots by O. Jinnouchi AN (%) Fit with CNI theory function (hep-ph/0305085) p = 3.9 GeV/c 100 GeV AGS preliminary p = 6.5 GeV/c RHIC preliminary Crosses zero p = 9.7 GeV/c 24 GeV 24 GeV p = 21.7 GeV/c Plot by S. Bravar 100 GeV 100 GeV Doesn’t cross zero recoil Carbon energy (keV) Igor Alekseev (ITEP)

11. Beam polarization profile (2005) 1mm Plots by I. Nakagawa Igor Alekseev (ITEP)

12. Roadmap to absolute polarization A JET target polarization Ptarget(Breit-Rabi polarimeter)    2%. BAN for elastic pp in CNI region: AN = - 1 / PtargeteN’. CPbeam = 1 /ANeN”. (B & C) can be combined in a single measurement: Pbeam/ Ptarget = - eN’ / eN”  stat  4% in 2 weeks (one ring) DCALIBRATION: ANpC for pC CNI polarimeter in covered kinematical range: ANpC = 1 / PbeameN”’. (B & C & D) measured simultaneously with several insertions of carbon target  stat(pC)  0% - very large statistics. E BEAM POLARIZATION:Pbeam = 1 / ANpCeN”” to experiments  (ANpC) < 1-2% if jet is run continuously. 2% 4% 1-2% 0% Igor Alekseev (ITEP)