1. Performance of the PHENIX Ring Imaging Cherenkov detector Takao Sakaguchi, CNS U. Tokyo, for the PHENIX Collaboration CNS, U. Tokyo (H. Hamagaki, T. Matsumoto, S. Nishimura, K. Oyama, T. Sakaguchi) Florida State U. (R. Chappell, D. Crook, A.D.Frawley, M. Kennedy) KEK (Y. Akiba, K. Shigaki) Nagasaki IAS (K. Ebisu, H. Hara, Y. Nagasaka, Y. Tanaka, T. Ushiroda) ORNL (M.S.Emerry, C.G.Moscone, J.W.Walker, A.L.Wintenberg, G.R.Young) SUNY at Stony Brook (R. Begay, J. Burward-Hoy, J.Ferriera, T.K.Hemmick, R.Hutter, S.Salomone) U. Tokyo (R.S.Hayano) Waseda U. (M.Hibino, S. Kametani, J. Kikuchi, M. Tamai) The PHENIX RICH Team consists of 32 scientists from 8 institutions! For Quark Matter 2001, Dec. 16, 2001

2. PHENIX Detector System Search for Quark Gluon Plasma phase in Hot Dense Matter produced by 100 GeV/u Au+Au at BNL RHIC (65 GeV/u Au+Au for Year-1) Central Arms Coverage (E&W) -0.35< y < 0.35 30 o <|  |< 120 o A complex apparatus to measure: Hadrons, Muons, Electrons, Photons Muon Arms Coverage (N&S) -1.2< |y| <2.3 -  <  <  View From Beam View From Top For Quark Matter 2001, Dec. 16, 2001

3. PHENIX RICH Cerenkov photons from e + or e - are detected by array of PMTs mirror Most hadrons do not emit Cerenkov light Electrons emit Cerenkov photons in RICH. Central Magnet ＲＩＣＨ PMT array Primary electron ID device of PHENIX Hadron rejection at 10 4 level for single track Full acceptance coverage for PHENIX central arms |y| < 0.35 ;  = 90 degrees x 2 Threshold gas Cherenkov C 2 H 6 (  th ~ 25) or CO 2 (  th ~ 35) eID p t range : 0.2 ~ 4 GeV/c PMT array readout 5,120 channels in 2 arms pixel size ~ 1 degree x 1 degree 2-D angles ( ,  ) of electron tracks were determined from center of Cerenkov ring, and associated with the tracks reconstructed by Drift Chamber(DC)+Pad Chamber(PC)+Time Expansion Chamber(TEC) For Quark Matter 2001, Dec. 16, 2001

4. Gas Vessel Two RICH detectors one for each arm - Weight: 7250 kg / arm - Gas volume: 40 m 3 / arm - Radiator length: 0.9 - 1.5 m - Mirror system Radius : 403 cm Surface area: 20 m 2 / arm - Photon detector: 2560 PMTs / arm - Radiation length Gas: 0.41 % (ethane) Windows: 0.2% Mirror panels: 0.53% Mirror support: 1.0% Total: 2.14% The vessels are designed and fabricated at Florida State University. For Quark Matter 2001, Dec. 16, 2001

5. RICH PMT Hamamatsu H3171S Cathode Diameter: 25 mm Tube Diameter: 29 mm Cathode: Bialkali Gain: > 10 7 Operation Voltage: - 1400 ~ -1800 V Dark current: < 100 nA at Gain=10 7 Cathode Luminous: >70 (mA/lm) Blue Sensitivity: > 9(mA/lm) Quantum efficiency: >19% at 300 nm >5 % at 200 nm Rise Time: < 2.5ns Transit Time Spread: < 750ps Total number of PMTs in RICH: 5120 Each PMT is housed in a magnetic shielding case –First 900 PMTs Soft iron and mu-metal –Other 4220 PMTs: FERROPERM (NKK) A Winstone cone shaped conical mirror is attached to each PMT to collect Cherenkov light –Entrance: 50 mm, Exit: 25 mm, Angular cut off: 30  Magnetic Shielding Case design For Quark Matter 2001, Dec. 16, 2001

6. RICH PMT array Supermodule are installed in RICH vessel to form a tightly packed PMT array 40 super-modules per one side of a RICH vessel, forming a 16x80 array Two arrays per RICH vessel, 4 arrays in two arms. Total number of PMTs: 5120 Completed PMT array of the first RICH detector. There is an identical PMT array in the opposite side of the RICH 32 PMTs are assembled into 2x16 sub-assembly called “super module” PMTs are grouped by its gain so that 8 tubes can share the same HV Supermodules are assembled and tested at Stony Brook, and sent to BNL At BNL, Winston cones are installed in PMTs, and the completed supermodules are installed in the RICH vessel Super Modules? For Quark Matter 2001, Dec. 16, 2001

7. RICH Mirror Segmented spherical mirror Radius: 403 cm 48 panels / arm 2 (side) x 2 (z) x 12 (  ) Reflection surface Aluminum Total area: 20 m 2 / area Mirror mounts are adjusted so that all optical targets are within 0.25 mm of the designed sperical surface. graphite fiber epoxy only 0.53 % of radiation length Mirror support structure graphite fiber, Delrin, 1 % of radiation length (ave.) Structure of the mirror Mirror panels are mounted by adjustable 3 point mounts on the frame bars 2 x 12 miror panels forms a spherical surface for one side of a RICH vessel 2 spherical surfaces in a vessel, total of 48 panels Completed mirror array of the first RICH Design of 3 points mirror mounts For Quark Matter 2001, Dec. 16, 2001

8. RICH (mirror alignment) After mirrors are installed, the RICH vessel is rotated up in the same orientation as on PHENIX carriage Positions of optical targets placed on mirror surface were surveyed with a computerized theodolite system (MANCAT). BNL survey crew were measuring the optical targets on the mirror during the mirror alignment. RICH (after mirror alignment) For Quark Matter 2001, Dec. 16, 2001

9. Readout Signals from 5120 PMTs: Zero  10 Photon Detection  0 pC  160 pC (Signal Preceded by Pre-Amp(x10) ) Time Resolution of  200 ps (For Background Rejection) Very Fast Operation: 9.6 MHz RHIC Beam Clock: Average Trigger Frequency  25 KHz Transfer to Data Collection Module (DCM)  Data Link using G-LINK Compactness  Processes 640 PMT Signals per Crate Conceptual Design of RICH FEE 9U VME Dimensions One Controller Module Two Trigger Modules and Readout Modules Ten AMU/ADC Modules Front End Electronics (FEE) RICH-FEE Crate ! For Quark Matter 2001, Dec. 16, 2001

10. Readout Module Controller Module Management of Analog Memory Unit (AMU) Controls FEE synchronous to Master Timing System Controls Burst Transfer Generate AMU Write / TAC Stop Timing Slow Serial Control using ARCNET DSU/ALM BTSK2 Readout FIFO G-Link Transmitter ROC Phase Shifter Transferring Data to PHENIX-DCM using G-LINK at the maximum speed of 800 Mbps G-LINK Transfer asynchronous to BUS Transfer inside RICH-FEE using four FIFOs (Depth: 9 events) Analog Processing (AMU/ADC) Module Integrator+TAC (RICH) Chip AMU/ADC Chip AMU/ADC Burst Controller 64 Inputs, 64 Charge and TAC(Timing) Outputs/Board Trigger Sum: 16 Trigger Sum Outputs/Board (4 PMT Signal Sum) Burst Transfer to Readout Module in 20-40MHz Serial Controllable ASICs on Board 8 RICH Chips (Integrator+VGA+LED+CFD+TAC+Trigger Sum) 8 Inputs, 8 CHARGE and TAC outputs/Chip, and 4 TriggerSum/Chip 4 AMU/ADC Chips (Random Accessible Analog Memory Unit and ADC) 32 Inputs/Chip For Quark Matter 2001, Dec. 16, 2001

11. RICH in Operation! (RHIC Year-1 RUN) High P T electron candidate is seen! Candidate selected with RICH, DC, and Electromagnetic Calorimeter (EMCal). For Quark Matter 2001, Dec. 16, 2001 PHENIX RUN 12280 SEQ 0014 EVENT 850 View from North Side South Side East ArmWest Arm RICH EMCal RICH ring (6 PMT hit) EMCal hit (2.5GeV) 6 PMT RICH ring 2.55 GeV/c track 2.5 GeV EMCal hit electron candidate EMCal RICH PC1 DC EMCal RICH PC1 DC TOF TEC PC3

12. RICH in Operation! (Cont’d) 4480 of 5120 (7/8) PMT signals are readout. Rests are not readout because of short of electronics Only 52 dead channels Used CO 2 as a Radiator gas Momentum acceptance down to 100 MeV/c is achieved Provide very good e/  separation RICH sees electrons in its geometrical acceptance Red: e -, Blue: e + For Quark Matter 2001, Dec. 16, 2001

13. RICH Hit and Multiplicity Number of PMTs fired has good correlation with number of PC1 hits which is corresponding to Multiplicity Occupancy at most central: 3.4 % (Magnetic field ON) Number of PMT hits Number of PC1 hits For Quark Matter 2001, Dec. 16, 2001

14. Electrons seen in Ratio of Energy and Momentum Ratio of energy (E) and momentum (p) of associated track Momentum and energy are measured with DC and EMCal, respectively Condition required PMT hits of more than two in the ring of 3.4cm<r<8.4cm Good ring shape Peak is seen at E/p=1, which corresponds to electrons Good separation of electrons is seen For Quark Matter 2001, Dec. 16, 2001 Green: Raw spectra Black: Cherenkov hit required Blue: Estimated background Red: Background subtracted 0.3GeV<p<0.4GeV0.6GeV<p<0.7GeV 0.8GeV<p<0.9GeV1.1GeV<p<1.2GeV

15. Charge Calibration with Real Data Fit pedestal for each RUN Count events above pedestal Exceed 5000? Accumulate more RUNs Fit single photo-electron (P.E.) Predict mean and sigma of double and triple P.E. Fit double and triple P.E. Using derived fit parameters, re-fit all P.E.s again Substitute pedestal-fit only RUNs with P.E.-fitted parameters NO YES 1.p.e. peak resolution:  = 0.42 p.e. After Calibration For Quark Matter 2001, Dec. 16, 2001

16. Timing Calibration with Real Data See the Timing data for identified Electron Hit. Correlate it with Beam Beam Counter (BBC) timing Determine Time 0 (T0) and conversion factor of RICH timing Data Recheck if (RICH T0 – BBC T0) are flat over entire BBC timing range  = 0.98 nsec Correlation of RICH T0 and BBC T0 Correlation of (RICH T0 - BBC T0) and BBC T0 Correction For Quark Matter 2001, Dec. 16, 2001

17. Photo-electrons seen in RICH Number of PMT hits, number of photo-electrons are in agreement with simulation study e + e - identified with Time of Flight (TOF) in the momentum range from 0.3GeV to 0.4GeV Overall figure of merit (N 0 ) is estimated: N 0 =N pe /L/ =119 cm -1 N pe : number of photo-electrons per ring L: path length in RICH vessel : mean cherenkov cone half-angle Black: Raw spectrum Blue: Background estimated Red: Background subtracted Number of PMTs per ring (r<11cm)Number of photoelectrons per ring (r<11cm) Number of photoelectrons divided by path length in RICH vessel (r<11cm) Mean=0.9798 For Quark Matter 2001, Dec. 16, 2001

18. RICH Ring Associated with Track RICH ring associated with DC+PC1+EMCal reconstructed track Final mirror alignment check is done with no field data in offline Main hits of PMTs are seen in about 3cm<r<11cm Low multiplicity events (PC1 hits<100) are selected More than four PMT hits in r<11cm are required Ring center deviation with reference to track:  =0.5 ,  z=3.3cm Good association is seen with track! For Quark Matter 2001, Dec. 16, 2001

19. Rejection Power of RICH (CO 2 Gas) Real Data e + e - and  +  - identified with TOF in the momentum range from 0.3GeV to 0.4GeV Efficiencies for electrons are  10% lower in this momentum range compared to those in the momentum range of simulation Number of PMTs are taken within ring of 3.4cm<r<8.4cm Ring shape cut is applied Timing cut is not applied (lose factor of two) Shielding for conversion electron at DC is not included (lose factor of two) Event class defined by PC1 hit: Peripheral: (PC1 hit)<150 Central: (PC1 hit)>400 Errors are statistical only Simulation Momentum range from 0.6 to 0.8GeV Au+Au Central Various electron ID cut is applied Timing cut applied Shielding included Black: Simulation for Au+Au Central Blue: Real data for Au+Au Peripheral Red: Real data for Au+Au Central For Quark Matter 2001, Dec. 16, 2001 Rejection Power is good, and will be much better after planned improvement

20. Very Near Future Plan Improve Rejection Power Shielding against conversion electron produced in the massive material at the edge of DC Establish Timing Cut Develop trigger board to associate with EMCal hits in online. Reaction rates at blue book luminosities 200 A GeV Au+Au: 1.2 kHz 200 GeV p+p: 400 kHz (4 MHz later) 500 GeV p+p: 1.2 MHz (12 MHz later) DAQ capability: level-1 limit : 25 kHz (6 kHz initially) required level-1 rejection power order of 10 2 ~ 10 3 for heavy ion physics Access to rare probes J  (di-electron) charm (single electron) Simulated Trigger Rejection Power for Au+Au Trigger Scheme RICH Trigger Board For Quark Matter 2001, Dec. 16, 2001

21. Summary RICH has succeeded to operate in the RHIC Year-1 RUN. High P T electrons are successfully identified. 7/8 of all PMTs (5120PMTs) have been readout with very few dead channels. Charge and timing calibration procedure using online data are established, and confirmed they work well. Following performances are derived. Timing resolution: ~ 1 nsec Charge resolution:  = ~ 1/2 p.e. for single photo-electron Overall figure of merit N 0 : 119 cm -1 Occupancy at most central: 3.4 % (Magnetic field on) Ring center deviation with reference to track:  =0.5 ,  z=3.3cm Rejection power at electron efficiency of 82%: 280 for Peripheral, 85 for Central (Without shielding for conversion electron and timing cut. Ring shape cut applied) Conversion electron shielding, timing cut will be applied for Year-2 RUN. RICH trigger board is developed and will be installed. For Quark Matter 2001, Dec. 16, 2001