Motivation for high-pt PID in PHENIX high-pt detector MRPC TOF in PHENIX Prototype runs

1. Time of Flight System for the PHENIX high-pT Detector UpgradeJulia Velkovska (Vanderbilt) , for PHENIX • Motivation for high-pt PID in PHENIX • high-pt detector • MRPC TOF in PHENIX • Prototype runs • Final design J.Velkovska PANIC05

2. Physics motivation for the high-pT detector Phys. Rev. Lett 91, 172301(2003). • Large suppression of p0 • Non-suppression of protons and anti-protons • Large baryon/meson ratios, a factor of 3 above standard fragmentation “ The large (anti)baryon to pion excess relative to expectations from parton fragmentation functions remains the most striking unpredicted experimental observation at RHIC. 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 • PID out to ~ 10 GeV needed ! J.Velkovska PANIC05

3. PID scheme with TOF, RICH and Aerogel • System requirements for TOF: • Resolution s < 100 ps • Efficiency > 95 % • Occupancy < 10 % • Total cost < 500k : MRPC TOF wins over scintillator TOF J.Velkovska PANIC05

4. The high-pT detector in PHEINIX • ACC installed in Run4 , Run5 • MRPC prototype tested in Run5 • Large area MRPC will be installed for Run6 J.Velkovska PANIC05

5. What is a MRPC ? J.Velkovska PANIC05

6. Honeycomb width = 12 cm Total active area width = 11.2 cm Strip width = 2.81 cm Readout strip thickness = 0.5 mm Strip interval = 0.3 cm PCB thickness = 1.5 mm Outer glass = 1.1 mm Inner glass = 0.55 mm carbon tape = 0.9 mm Mylar thickness = 0.25 mm Honeycomb thickness = 9.5 mm Inner glass width = 11.2 cm Outer glass width = 11.5 cm Glass Electrode Mylar PC board Readout pad Honeycomb Standoff PCB width = 13 cm PCB length = 42.8 cm Outer glass length = 37.4 cm Strip length = 37 cm Honeycomb = 38 cm Inner glass length = 37 cm PHENIX MRPC final design Gas gap = 0.23 mm J.Velkovska PANIC05

7. Here is how an early prototype looked: …now the honeycomb is thinner, the spacers are the exact size, the strips have slightly different dimensions, but the internal structure is the same J.Velkovska PANIC05

8. 3 Prototypes tested at KEK in June 2004 PH1 PH2 PH3 • Different pad/strip design, same structure inside • PH1: 50.9 x 53.5 cm2, 32 strips, readout at both ends. • PH2: 12.5 x 53.5 cm2, 8 strips, readout at both ends. • PH3: 12.7 x 53.7 cm2, 48 pads (6x2 cm2), similar to STAR MRPC. J.Velkovska PANIC05

9. KEK T1 beam line J.Velkovska PANIC05

10. + p PH2 Streamer Avalanche efficiency T = 68 ps (best value) J.Velkovska PANIC05

11. KEK beam test results Efficiency Time Resolution Gas mixture:95%/5% r134a, iC4H10 • 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. J.Velkovska PANIC05

12. To test TOF.W prototype in the PHENIX environment Test 3 prototypes for 3 months continuous operation in AA beam conditions Operate the detector within PHENIX Check timing resolution and efficiency To test electronics chain ( pre-amp +FEMs) Can we use analog signal (only) from RICE pre-amp + TOF.E design FEMs and retain the timing resolution obtained in test beam at KEK RUN5 goals J.Velkovska PANIC05

13. RUN5 configuration: 2 boxes as shown PH4 PH4 PH3 PH2 • PH2 and PH3 previously tested. PH4 – wider strips – considered for final design J.Velkovska PANIC05

14. RUN 5: MRPCs before installation • 192 electronics channels instrumented • To test digitization on-board vs digitization in the FEMs : both analog and digital signals were read-out from selected strips • Digitization in FEMs desirable because: • Proven technology (used since day1 in TOF-East) • Less dissipated power at the detector – can operate with air cooling J.Velkovska PANIC05

15. RUN 5 results : timing resolution • Comparable performance in both read-out chains • Resolution for full start ( BBC) + stop (MRPC) ~ 100 ps • Design goal for both detector and electronics is met ! J.Velkovska PANIC05

16. 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 m2 • Pre-amplification of signals at the detector • Analog signal recorded in FEM ( to be used for slewing corrections). Digitization in FEM J.Velkovska PANIC05

17. Final detector: mechanics • Checkerboard pattern of MRPC+preamp electronics • optimize active area • Keep the electronics outside the box to limit noise • Fit into 3” of radial space available in PHENIX West arm • The most complicated part Vanderbilt machine shop has ever built J.Velkovska PANIC05

18. Summary and status • In the period Jan 2004 – Oct 2005 we have gone from conceptual ideas to final detector construction ( help from our STAR 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. • Status today: • All detector modules produced • Extremely tight schedule for electronics production • We expect to install at least half of the full system in 3 weeks • I hope that my next talk will be about physics produced with the new TOF detector ! J.Velkovska PANIC05