1. JUNE 1997PHOBOS Review Mark D. Baker PHOBOS Review Physics Simulations Mark D. Baker Physics PHOBOS design is sound. –( & PHOBOS Computing Project is on track.)

2. JUNE 1997PHOBOS Review Mark D. Baker PHOBOS Physics Goals 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 Study QCD confinement and vacuum

3. JUNE 1997PHOBOS Review Mark D. Baker Detailed GEANT simulation

4. JUNE 1997PHOBOS Review Mark D. Baker 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

5. JUNE 1997PHOBOS Review Mark D. Baker Event-by-Event Multiplicity Instrumental uncertainty:

6. JUNE 1997PHOBOS Review Mark D. Baker Event-by-event dN/d 

7. JUNE 1997PHOBOS Review Mark D. Baker 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  , 

8. JUNE 1997PHOBOS Review Mark D. Baker Measurement of secondaries PHOBOS testbeam data (May ‘97) Thin = 6 mm, Thick = 6 cm Beampipe: Supports: Magnet:

9. JUNE 1997PHOBOS Review Mark D. Baker Measurement of secondaries PHOBOS: Very preliminary data. (May ‘97) Beam thru hole: 50k pions @ 5GeV

10. JUNE 1997PHOBOS Review Mark D. Baker Measurement of secondaries PHOBOS: Very preliminarydata! (May ‘97) Fe targetNo target Beam hits detector: Beam thru hole: 5 GeV beam:

11. JUNE 1997PHOBOS Review Mark D. Baker 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.

12. JUNE 1997PHOBOS Review Mark D. Baker Hough Tracking Event Display Placeholder only. Will use baker_sideways.ppt

13. JUNE 1997PHOBOS Review Mark D. Baker Efficiency and Ghosts Full GEANT simulation –100% efficient planes Hough Transform –Tight cuts Results: –85% efficiency –No p dependence –Ghosts negligible

14. JUNE 1997PHOBOS Review Mark D. Baker Momentum Resolution

15. JUNE 1997PHOBOS Review Mark D. Baker Tracking vs. Plane Efficiency No major problem –1% plane inefficiency 2% tracking inefficiency –Probably improvable (better covariance matrices)

16. JUNE 1997PHOBOS Review Mark D. Baker Track finding - very low Pt  deg   deg  7 planes, E>800 keV 7 planes, all hits 80 602040 204060 80 0 0 -8 8 8 Stopping Kaon

17. JUNE 1997PHOBOS Review Mark D. Baker Particle ID by dE/dx safe extended

18. JUNE 1997PHOBOS Review Mark D. Baker Particle ID - very low Pt

19. JUNE 1997PHOBOS Review Mark D. Baker Particle ID - very low Pt mass parameter

20. JUNE 1997PHOBOS Review Mark D. Baker Spectrometer Acceptance

21. JUNE 1997PHOBOS Review Mark D. Baker HBT Acceptance Truth Resolution smeared

22. JUNE 1997PHOBOS Review Mark D. Baker PHOBOS HBT Capabilities “Standard” Scenario –Extrapolate from low E Exotic Scenario I –Very large source

23. JUNE 1997PHOBOS Review Mark D. Baker PHOBOS HBT Capabilities “Standard” Scenario –Extrapolate from low E Exotic Scenario II –Very rapid expansion

24. JUNE 1997PHOBOS Review Mark D. Baker 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.

25. JUNE 1997PHOBOS Review Mark D. Baker Phi Rates Assumptions: –15  K K / central event –100 Hz central events (15% central & vtx cut) –Yields: 9x10  K K /nominal week Reconstructed  K K –1 nominal week (15% central cut) Si-extended + TOF: 230,000 Si-only conservative PID: 50,000 +  +   + 

26. JUNE 1997PHOBOS Review Mark D. Baker Phi Resolution Resolution:  (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)

27. JUNE 1997PHOBOS Review Mark D. Baker Phi Width Measurement Placeholder only see baker_sideways.ppt

28. JUNE 1997PHOBOS Review Mark D. Baker Phi Width Measurement Placeholder only see baker_sideways.ppt

29. JUNE 1997PHOBOS Review Mark D. Baker Computing Organization ~9 FTEs total 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

30. JUNE 1997PHOBOS Review Mark D. Baker Conclusions Physics capabilities look good! –N, dN/d  –HBT –Phi mass Technical capabilities look good –Track Finding –Particle ID –Low p acceptance T