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PHOBOS Review Physics Simulations Mark D. Baker

PHOBOS Review Physics Simulations Mark D. Baker. Physics PHOBOS design is sound. ( & PHOBOS Computing Project is on track.). PHOBOS Physics Goals. Study QCD confinement and vacuum. Typical physics topics: Look for Excess Entropy Source Size & Lifetime (HBT)

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PHOBOS Review Physics Simulations Mark D. Baker

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  1. PHOBOS Review Physics SimulationsMark D. Baker • Physics PHOBOS design is sound. • ( & PHOBOS Computing Project is on track.) PHOBOS Review Mark D. Baker

  2. PHOBOS Physics Goals Study QCD confinement and vacuum • Typical physics topics: • Look for Excess Entropy • Source Size & Lifetime (HBT) • Multiplicity distributions and fluctuations • Look for collective phenomena (over large V) • Low transverse momentum • Look for unusual medium effects • Phi mass and width PHOBOS Review Mark D. Baker

  3. Detailed GEANT simulation PHOBOS Review Mark D. Baker

  4. Types of Uncertainties • Statistical (Poisson) • Unavoidable in event-by-event physics • Can be made negligible for distributions • Instrumental • Fluctuations in non-ideal detector • Landau fluctuations • Secondary production, etc. • Systematic PHOBOS Review Mark D. Baker

  5. Event-by-Event Multiplicity Instrumental uncertainty: PHOBOS Review Mark D. Baker

  6. Event-by-event dN/dh PHOBOS Review Mark D. Baker

  7. Measuring Multiplicity Corrections • Spectrometer • Measure p distributions for primaries • Measure dE/dx distribution directly • Vertex Detector • Measure dE/dx directly • Multiplicity Detector: • Effective measurement of most secondaries: • Primaries: independent of Zvtx,f , h -h. PHOBOS Review Mark D. Baker

  8. Measurement of secondaries PHOBOS testbeam data (May ‘97) Beampipe: Supports: Magnet: Thin = 6 mm, Thick = 6 cm PHOBOS Review Mark D. Baker

  9. Measurement of secondaries Beam thru hole: 50k pions @ 5GeV PHOBOS: Very preliminary data. (May ‘97) PHOBOS Review Mark D. Baker

  10. Measurement of secondaries 5 GeV beam: Fe target No target Beam hits detector: Beam thru hole: PHOBOS: Very preliminarydata! (May ‘97) PHOBOS Review Mark D. Baker

  11. Tracking Results • Hough Transform Studies • Limited acceptance, non-GEANT • Spectrometer design optimized and validated • Efficiency & ghost rate acceptable • Full acceptance GEANT studies • Validated above results • Template Tracking Code • Limited acceptance, non-GEANT • Fully integrated in ROOT/C++ • Results look good. PHOBOS Review Mark D. Baker

  12. Hough Tracking Event Display Placeholder only. Will use baker_sideways.ppt PHOBOS Review Mark D. Baker

  13. Efficiency and Ghosts • Full GEANT simulation • 100% efficient planes • Hough Transform • Tight cuts • Results: • 85% efficiency • No p dependence • Ghosts negligible PHOBOS Review Mark D. Baker

  14. Momentum Resolution PHOBOS Review Mark D. Baker

  15. Tracking vs. Plane Efficiency • No major problem • 1% plane inefficiency 2% tracking inefficiency • Probably improvable (better covariance matrices) PHOBOS Review Mark D. Baker

  16. Track finding - very low Pt 8 7 planes, E>800 keV StoppingKaon f (deg.) 0 -8 20 40 60 q (deg.) 80 8 7 planes, all hits f (deg.) 0 -8 20 40 60 q (deg.) 80 PHOBOS Review Mark D. Baker

  17. Particle ID by dE/dx safe extended PHOBOS Review Mark D. Baker

  18. Particle ID - very low Pt PHOBOS Review Mark D. Baker

  19. Particle ID - very low Pt mass parameter mass parameter PHOBOS Review Mark D. Baker

  20. Spectrometer Acceptance PHOBOS Review Mark D. Baker

  21. HBT Acceptance Truth Resolution smeared PHOBOS Review Mark D. Baker

  22. PHOBOS HBT Capabilities • Exotic Scenario I • Very large source • “Standard” Scenario • Extrapolate from low E PHOBOS Review Mark D. Baker

  23. PHOBOS HBT Capabilities • Exotic Scenario II • Very rapid expansion • “Standard” Scenario • Extrapolate from low E PHOBOS Review Mark D. Baker

  24. HBT Summary • We can measure 20 fm sources accurately. • 10% systematics with simple analysis • Easily improved. • We can distinguish interesting physics from a simple baseline extrapolation. PHOBOS Review Mark D. Baker

  25. Phi Rates • Assumptions: • 15 f K K / central event • 100 Hz central events (15% central & vtx cut) • Yields: 9x10 f K K /nominal week • Reconstructed f K K • 1 nominal week (15% central cut) • Si-extended + TOF: 230,000 • Si-only conservative PID: 50,000 + - 8 + - + - PHOBOS Review Mark D. Baker

  26. Phi Resolution • Resolution: s(Minv) = 1.6 MeV • Dominated by momentum resolution • Calculated 2 ways: • Fast Simulation • Analytic propagation of errors • Error on Width (after 1 nominal week) • 0.7 MeV (extended-dE/dx + TOF) • 1.0 MeV (conservative-dE/dx only) PHOBOS Review Mark D. Baker

  27. Phi Width Measurement Placeholder only see baker_sideways.ppt PHOBOS Review Mark D. Baker

  28. Phi Width Measurement Placeholder only see baker_sideways.ppt PHOBOS Review Mark D. Baker

  29. Mark Baker Chris Conner Patrick Decowski Rudi Ganz Edmundo Garcia-Solis Clive Halliwell Don McLeod Andrzej Olszewski Lou Remsberg Gunther Roland Ashutosh Sanzgiri George Stephans Cyrus Taylor Adam Trzupek Robin Verdier Frank Wolfs Barbara Wosiek Krzysztof Wozniak Computing Organization ~9 FTEs total PHOBOS Review Mark D. Baker

  30. Conclusions • Physics capabilities look good! • N, dN/dh • HBT • Phi mass • Technical capabilities look good • Track Finding • Particle ID • Low p acceptance T PHOBOS Review Mark D. Baker

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