pC polarimeter at RHIC. Status and performance. 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 of Wisconsin, 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 IX WORKSHOP ON HIGH ENERGY SPIN PHYSICS, Dubna, September 27 - October 1, 2005

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

Igor Alekseev (ITEP) 3 Challenge 1.Absolute polarization measurement with  P beam / P beam < 0.05 for experiments. 2.Fast (< 5 min) measurement for accelerator debugging. 3.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 P target (Breit-Rabi polarimeter) B A N for elastic pp in CNI region: A N = - 1 / P target  N ’ C P beam = 1 / A N  N ” (B & C) can be combined in a single measurement: P beam / P target = -  N ’ /  N ” “self calibration” works for elastic scattering only D CALIBRATION: A N pC for pC CNI polarimeter in covered kinematical range: A N pC = 1 / P beam  N ”’ (B & C & D) measured simultaneously with several insertions of carbon target E BEAM POLARIZATION: P beam = 1 / A N pC  N ”” to experiments 1.Absolute polarization measurement with  P beam / P beam < 0.05 for experiments. 2.Fast (< 5 min) measurement for accelerator debugging. 3.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 P target (Breit-Rabi polarimeter) B A N for elastic pp in CNI region: A N = - 1 / P target  N ’ C P beam = 1 / A N  N ” (B & C) can be combined in a single measurement: P beam / P target = -  N ’ /  N ” “self calibration” works for elastic scattering only D CALIBRATION: A N pC for pC CNI polarimeter in covered kinematical range: A N pC = 1 / P beam  N ”’ (B & C & D) measured simultaneously with several insertions of carbon target E BEAM POLARIZATION: P beam = 1 / A N pC  N ”” to experiments

Igor Alekseev (ITEP) 4 EM spin-flip amplitude hadronic non spin-flip amplitude A N arises mainly from interference between EM spin-flip amplitude and hadronic non spin-flip amplitude (CNI = Coulomb – Nuclear Interference) Elastic scattering in the CNI region  m,p M TRTR All kinematics is defined by recoil particle. For all RHIC beam energies recoil particle goes at 90 o. Analyzing power small, but with weak energy dependence. Large cross section  very good figure of merit. Need to collect 2-5  10 7 events per measurement. Energy of the recoil particle is very small  target must be extremely thin. Pure CNI Regge poles /Pomeron exchange A N is also sensitive probe to hadronic spin flip amplitude

Igor Alekseev (ITEP) 5 pC polarimeter setup Ultra thin Carbon ribbon Target (3.5  g/cm 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 No dead time !

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

Igor Alekseev (ITEP) 7 FPGA algorithms baseline A MAX /4 A MAX t CFD t MAX Pipeline (for each bunch crossing) Baseline subtraction A MAX and t MAX Integral t CFD Use A MAX versus t CFD 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 2·10 8 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. 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 2·10 11 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) Invariant Mass M C ~ GeV  M ~ 1.5 GeV carbon alpha prompts Plots by O. Jinnouchi

Igor Alekseev (ITEP) 10 pC: shape is different ! Re r 5 =0, Im r 5 =0 no hadron spin-flip p = 3.9 GeV/c p = 6.5 GeV/c p = 9.7 GeV/c p = 21.7 GeV/c AGS preliminary A N (%) recoil Carbon energy (keV) 100 GeV 24 GeV 100 GeV RHIC preliminary Fit with CNI theory function (hep-ph/ ) Crosses zero Doesn’t cross zero 24 GeV 100 GeV Plots by O. Jinnouchi Plot by S. Bravar

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 P target (Breit-Rabi polarimeter)    2%. B A N for elastic pp in CNI region: A N = - 1 / P target  N ’. C P beam = 1 / A N  N ”. (B & C) can be combined in a single measurement: P beam / P target = -  N ’ /  N ”   stat  4% in 2 weeks (one ring) D CALIBRATION: A N pC for pC CNI polarimeter in covered kinematical range: A N pC = 1 / P beam  N ”’. (B & C & D) measured simultaneously with several insertions of carbon target   stat (pC)  0% - very large statistics. E BEAM POLARIZATION: P beam = 1 / A N pC  N ”” to experiments   (A N pC ) < 1-2% if jet is run continuously. A JET target polarization P target (Breit-Rabi polarimeter)    2%. B A N for elastic pp in CNI region: A N = - 1 / P target  N ’. C P beam = 1 / A N  N ”. (B & C) can be combined in a single measurement: P beam / P target = -  N ’ /  N ”   stat  4% in 2 weeks (one ring) D CALIBRATION: A N pC for pC CNI polarimeter in covered kinematical range: A N pC = 1 / P beam  N ”’. (B & C & D) measured simultaneously with several insertions of carbon target   stat (pC)  0% - very large statistics. E BEAM POLARIZATION: P beam = 1 / A N pC  N ”” to experiments   (A N pC ) < 1-2% if jet is run continuously. 2%4%1-2%0%