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PID Capability of MRPC-TOF at STAR at RHIC

PID Capability of MRPC-TOF at STAR at RHIC. L ijuan Ruan ( Lawrence Berkeley National Laboratory ) for the STAR Collaboration. Outline: Motivation Detector and Timing Resolution PID Capability  Hadron PID up to intermediate and high p T  Electron PID Summary and Outlook.

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PID Capability of MRPC-TOF at STAR at RHIC

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  1. PID Capability of MRPC-TOF at STAR at RHIC LijuanRuan (Lawrence Berkeley National Laboratory) for the STAR Collaboration Outline: • Motivation • Detector and Timing Resolution • PID Capability •  Hadron PID up to intermediate and high pT •  Electron PID • Summary and Outlook RHIC-AGS User Meeting, BNL

  2. Motivation • PID from TPC dE/dx: /k ~0.7 GeV/c, (,k)/p ~1.1 GeV/c need to extend hadron PID up to intermediate and high pT region. • With good timing resolution < 100 ps, detecting efficiency > 95%, and low cost, MRPC-TOF is the solution. • Physics: Hadron PID: high pT leading hadron correlation … Electron PID: charm, charmonium, vector meson physics. RHIC-AGS User Meeting, BNL

  3. STAR Detector: TPC & MRPC-TOFr • A new technology ---- • Multigap Resistive Plate Chamber(MRPC) • adopted from CERN-Alice. • A prototype detector of time-of- flight (TOFr) has been installed since year3, 0.3% of TPC acceptance. • Intrinsic timing resolution: 85 psin Run III, IV, V. RHIC-AGS User Meeting, BNL

  4. Timing Resolution Summary Within typical scintillator resolution, but ~ 5 times cheaper RHIC-AGS User Meeting, BNL

  5. Hadron PID TPC alone: /k ~0.7 GeV/c, (,k)/p ~1.1 GeV/c TOF alone:  /k ~1.6 GeV/c, (,k)/p ~ 3.0 GeV/c STAR Collaboration, PLB 616 (2005) 8 RHIC-AGS User Meeting, BNL

  6. Momentum: GeV/c • dE/dx of p are2 separated from those of K and p. Relativistic Rise of pion dE/dx log10(dE/dx (KeV/cm)) log10(p (GeV/c)) RHIC-AGS User Meeting, BNL

  7. Hadron PID at intermediate pT Combine TPC (n,K,p) and TOF (m2) information, the PID range could be greatly extended: ,p up to 5 GeV/c, K up to 3 GeV/c p K  yield_ = 2*yield_(n>0), if the n is a normal Gaussian distribution Ming Shao et al., nucl-ex/0505026 RHIC-AGS User Meeting, BNL

  8. Do we know where dE/dx is? TOFr PID Cross Check m2 Ming Shao et al., nucl-ex/0505026 RHIC-AGS User Meeting, BNL

  9. Do we know where dE/dx is? Au+Au 62 GeV Charged hadron Cross Check Au+Au 62 GeV The TOF PID and charge hadron cross checks confirm that the Bichsel Function can be used to constrain the relative dE/dx position between , kaon and proton. go to high pT. Ming Shao et al., nucl-ex/0505026 RHIC-AGS User Meeting, BNL

  10.  and proton PID at high pT Au+Au 200 GeV Run II Au+Au 62 GeV Ming Shao et al., nucl-ex/0505026 O. Barannikova et al., nucl-ex/0505021 , proton can be identified up to pT 10 GeV/c RHIC-AGS User Meeting, BNL

  11.  and proton PID at high pT Au+Au 200 GeV Run II O. Barannikova et al., nucl-ex/0505021 , proton can be identified up to pT 10 GeV/c RHIC-AGS User Meeting, BNL

  12. MRPC-TOFr Electron PID electrons Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!! STAR Collaboration, PRL 94, 2005, 062301 Clean electron PID can be obtained up to PT< 3 GeV/c.  This is used to measure the semileptonic decay of open charm. RHIC-AGS User Meeting, BNL

  13. Conclusions • 85 ps intrinsic timing resolution was achieved in run 3, run4 and run 5 from MRPC-TOFr at STAR. • By combining the measurements from TPC and TOF,  and proton can be identified up to pT10 GeV/c, kaon up to 3 GeV/c. This will significantly extend the pT reach of resonance measurements with Full TOF coverage ( |η|<1, 2π azimuth coverage, 10%~15% occupancy in central AuAu collision at 200 GeV). • Clean electron PID was obtained at pT<3 GeV/c. This will make the measurements of vector meson dileptonic decays possible at RHIC. RHIC-AGS User Meeting, BNL

  14. Outlook: Vector Meson Di-leptonic Decay Electrons from gamma conversion • Full MRPC-TOF: • Clean Electron PID • TPC+SVT+μVertex: • ~98% electrons from gamma conversion rejected Let’s measure the dileptonic decay of vector meson at RHIC ! RHIC-AGS User Meeting, BNL

  15. Related Publications • Physics Results: Run III: Open charm yields in d+Au collisions, PRL 94 (2005) 062301 Cronin effect of identified particle at RHIC, PLB 616 (2005) 8 • NIM paper: Run II: W.J. Llope et al., Nucl.Instrum.Meth.A522:252-273,2004 Run III: J. Wu et al., Nucl.Instrum.Meth.A538:243-248,2005 Run IV: M. Shao et al., nucl-ex/0505026 • Proceedings of Conference and Workshops: L.J. Ruan et al., J.Phys.G31:S1029-S1034,2005 M. Shao et al., J.Phys.G31:S85-S92,2005 F. Geurts et al., Nucl.Instrum.Meth.A533:60-64,2004 …… Thank you very much! RHIC-AGS User Meeting, BNL

  16. Back Up RHIC-AGS User Meeting, BNL

  17. STAR Preliminary -(K+p) Separation • Worst Contamination: 1-3% at 50% Eff , 10% at 70-90% Eff • 3 Gauss fits: dE/dx(p)>1.3*dE/dx(K)dE/dx(p) as normal Gauss:s=1, mean=0 • -(K+p) Separation: ~1.5-2 RHIC-AGS User Meeting, BNL

  18. Physics Measurements which require or benefit from TOF RHIC-AGS User Meeting, BNL

  19. Physics Measurements which require or benefit from TOF(cont.) RHIC-AGS User Meeting, BNL

  20. Specific Examples of Benefit of TOF: Do→ Kp in central Au-Au collisions Number of central Au-AU events required to see 3s signal FOM (figure of merit) = reduction in data set required by using TOF PID RHIC-AGS User Meeting, BNL

  21. Specific Examples of Benefit of TOF: Resonances in central Au-Au collisions TOF PID also reduces systematic errors from correlated background due to misidentified particles RHIC-AGS User Meeting, BNL

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