1. NSS2006Shengli Huang1 The Time of Flight Detector Upgrade at PHENIX Shengli Huang PHENIX Collaboration Outlines: 1.Physics motivations 2.Multi-gap Resistive plate chamber 3.The test beam and Run5 testing results 4.The installation for Run7 5.Conclusions

2. NSS2006Shengli Huang2 Physics motivation for the high-pT detector Phys. Rev. Lett 91, 172301 (2003). Large suppression of    while not protons Large baryon/meson ratios, a factor of 3 above standard fragmentation The data clearly indicates that a new mechanism other than universal parton fragmentation is the dominant source of baryons and anti-baryons in the intermediate pT range in heavy ion collisions. Phenix White paper How about the flavor dependence of energy loss in the higher p T region? X.N. Wang, Phys. Rev. C 58, 2321 (1998). PID out to ~ 10 GeV needed !

3. NSS2006Shengli Huang3 Jet correlations with identified mesons and baryons jet partner equally likely for trigger baryons & mesons, expected from purely thermal recombination (nucl-th/0306027) Need partons from jets to explain the data!! To improve this measurement High-pt PID in both arms Full azimuthal coverage for  Phys. Rev. C 71, 051902(R) (2005)

4. NSS2006Shengli Huang4 Track-by-track high p T PID upgrade With 100ps timing resolution 1)TOF will let the Aerogel detector be well calibrated 2)Aerogel together with TOF can extend the PHENIX track-by- track PID capability to 10 GeV/c 3)Two pieces of TOFw will supply full  coverage for jet correlation measurement High p T PID detector: 1.Areogel Cherenkov n=1.011 2.MRPC TOF  ~100ps

5. NSS2006Shengli Huang5 Ionization Process Avalanche Process Signal Induced Process Multi-gap Resistive Plate Chamber MRPC

6. NSS2006Shengli Huang6 MRPC for PHENIX TOFw 6 gaps (230 micron). Gas mixture: R134A (95%), Isobutene (5%) HV:  7.0~7.5 kV Gas gap = 0.23 mm Readout strip thickness = 0.5 mm Total active area width = 11.2 cm Honeycomb width = 12 cm Glass Electrode Mylar PC board Readout pad Honeycomb Standoff Inner glass width = 11.2 cm Outer glass width = 11.5 cm PCB width = 13 cm Outer glass = 1.1 mm Inner glass = 0.55 mm carbon tape = 0.9 mm Mylar thickness = 0.25 mm PCB thickness = 1.5 mm Honeycomb thickness = 9.5 mm Strip width = 2.81 cm Strip interval = 0.3 cm PHENIX-MRPC: Final Version  Good timing resolution  High efficiency  Cheap for mass production

7. NSS2006Shengli Huang7 Prototypes tested at KEK in June 2004 PH1 PH2 PH3 Different pad/strip design, same structure inside PH1: 50.9 x 53.5 cm 2, 32 strips, readout at both ends. PH2: 12.5 x 53.5 cm 2, 8 strips, readout at both ends. PH3: 12.7 x 53.7 cm 2, 48 pads (6x2 cm 2 ), similar to STAR MRPC.

8. NSS2006Shengli Huang8 KEK beam test results Time Resolution Efficiency PH1: worse timing resolution (>150 ps), same efficency as PH2. Problem on uniformity of performance across the chamber. Difficulties in mechanical assembly. PH2: 68ps timing resolution at optimal condition, but 90% efficiency. Solution  increase strip width. PH3: comparable timing resolution with PH2 (best value: 67ps), 98% efficiency. Gas mixture:95%/5% r134a, iC 4 H 10

9. NSS2006Shengli Huang9 Run5 Beam Results for Final Version Test different MRPC prototypes. Test different electronic chains

10. NSS2006Shengli Huang10 Final Design 1024 readout channels 128 MRPCs, 4 strips/each with double ended readout (detailed dimensions on slide 6) 4 gas volumes. Total active area ~ 8 m 2 Pre-amplification of signals at the detector Analog signal recorded in FEM ( to be used for slewing corrections). Digitization in FEM

11. NSS2006Shengli Huang11 TOF West Installation for Run7 Mechanical Installation Complete Gas System, HV, LV -- operational FEM installation and testing - ongoing

12. NSS2006Shengli Huang12 Conclusions/Outlook In the period Jan 2004 – Oct 2005 we have finished the R&D for the new TOF ( help from our colleagues at RICE university is gratefully acknowledged). A complete detector + electronics chain was successfully operated within PHENIX for 3 months in heavy ion beam conditions in 2005. All design goals were met.  ~100ps, efficiency>90% In the summer of 2006, the whole new TOF has been successfully installed The physics produced with the new TOF detector will be expected from the coming 2007 Run