1. Performance of the PHENIX Muon Identifier Introduction Calibration with cosmic rays Performance in Au+Au collisions Summary Hiroki Sato, Kyoto University for the PHENIX Collaboration Outline First Joint Meeting of the Nuclear Physics Divisions of APS and JPS October 17, 2001 Wailea, Maui, Hawaii

2. Physics with the PHENIX Muon Arms QGP signals in Au+Au collisions –J/  suppression –  mass shift –Charm enhancement ← , e  Proton spin structure with polarized p+p collisions –Double-longitudinal spin asymmetry for J/  and open heavy flavor production →  G(x) –Parity violating spin asymmetry for W boson production →  q(x) - ← 

3. The PHENIX Muon Arms Muon Tracker (MuTr) Cathode-readout strip chambers at three stations  x ~ 100  m →Δp/p~3%@3~10GeV/c Muon Identifier (MuID) 5 layers of chambers (Iarocci tubes) sandwiched in steel  misidentification probability ~ 3  10 -4 used as a trigger counter Acceptance: 1.2 < |  | < 2.4 Total absorber ~ 10λ int Minimum Momentum ~ 2GeV/c 2001 South Muon Arm operation started 2002~ Both Arms operation Muon Identifier Muon Tracker Muon Magnet South Muon ArmNorth Muon Arm

4. MuID Structure 4 large panels and 2 small panels in one layer (gap) In a panel, Iarocci tubes with 2.5~5.6m length and 8.4cm width run both horizontally and vertically 6340 tubes ( 3170 channels ) / Arm South Muon Arm North Arm One channel consists of two staggered tubes for better efficiency and faster drift time Those two layers are in different HV and gas chains to minimize dead channels Large panelSmall panel

5. Cosmic rays are found! Both hardware and software (road-finder, event display, …) are confirmed to be working well. Roads matches clusters in MuTr. Useful for calibration of both MuID and MuTr. Used MuID NIM-logic trigger → talked by Ken Read (next speaker) Reconstructed road (track in MuID) MuID panel Hit tubes MuTr clusters Hit tube cross points

6. HV/threshold Scan for Efficiency ~95% tube efficiency is achieved threshold = 90mV HV = 4300V No threshold dependence →set to 90mV Noise is serious < 60mV Nice plateau for 4300~4500V → Operation Voltage is set Threshold = 90mV

7. Geometry check Geometry is confirmed to be OK Number of panels  x (cm) Number of panels reconstructed road Fired tube (2-pack) xx. Number of roads(hits) Mean DistributionRMS Distribution cm

8. Roads Found in Au+Au Collisions! The entire South MuID is being operated in Au+Au collisions ar  s NN = 200GeV Road-finder is working well in Au+Au collision MuID road Au+Au collision  s NN = 200GeV MuTr clusters MuID hit tubes MuID Road

9. Correlation with Beam-Beam Counter Total number of hits in the South MuID is clearly correlated with the charge sum in the Beam-Beam Counter(3.1<|  |<4) Confirms MuID is observing collisions Total number of hits in MuID Charge Sum of Beam-Beam Counter

10. Tube Hit Rates Hit rates agree with simulation well Tube y position(cm) Gap3 (4 th gap), Panel0, Horizontal Number of hits/event Gap 3, Panel0, Vertical Tube x position(cm) Number of hits/event Panel 0 Viewed From IP Red: Data Blue: HIJING simulation Red: Data Blue: HIJING simulation

11. Road Density Road position distribution agrees with simulation Number of Roads/event/bin Gap 0 Position(cm) Red: Data Blue: HIJING simulation Event vertex

12. Road efficiency in Au+Au collisions Single muons ( Pz = 5GeV/c and  = 20deg. ) mixed with HIJING events ‘Good’ road means 2/3 of hits of a road comes from the signal muon. ~70% of ‘good’ road efficiency will be achieved at most central events simulation Single  (Pz = 5GeV/c,  = 20deg) + HIJING Au+Au  s=200GeV 95% tube efficiency Most Peripheral Most Central

13. Summary Both hardware and software are confirmed to be working fine with cosmic ray data and chamber efficiency was found to be about 95%. The entire South MuID is successfully being operated in Au+Au collisions. Hit rates and road density agree with simulation well. Road-finder works even at most central Au+Au events.

14. Top view Side view Front view

15. Geometry check Geometry is confirmed to be OK Number of panels  x (cm) Number of panels reconstructed road Fired tube (2-pack) xx. Number of roads(hits)