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JUNE 1997 PHOBOS Review Mark D. Baker
PHOBOS Review Physics Simulations
Mark D. Baker
• Physics PHOBOS design is sound.– ( & PHOBOS Computing Project is on track.)
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JUNE 1997 PHOBOS 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
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JUNE 1997 PHOBOS Review Mark D. Baker
Detailed GEANT simulation
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JUNE 1997 PHOBOS 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
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JUNE 1997 PHOBOS Review Mark D. Baker
Event-by-Event Multiplicity
Instrumental uncertainty: N3
250
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JUNE 1997 PHOBOS Review Mark D. Baker
Event-by-event dN/d
5938trueN6122. avgN
.)(51.)(775881 inststatNmeas .)(51.)(775881 inststatNmeas
5938trueN
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JUNE 1997 PHOBOS 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 ,
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JUNE 1997 PHOBOS Review Mark D. Baker
Measurement of secondariesPHOBOS testbeam data (May ‘97)
Target Beam mom. Chg. # ev.
Empty 2-5 GeV/c - 600k
Thin Be 0.5-5 GeV/c +/- 900kThick Be 5 GeV/c - 230k
Thin Al 4 GeV/c - 50kThick Al 5 GeV/c - 220k
Thin Fe 5 GeV/c - 200kThick Fe 5 GeV/c - 100k
Thin = 6 mm, Thick = 6 cm
Beampipe:
Supports:
Magnet:
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JUNE 1997 PHOBOS Review Mark D. Baker
Measurement of secondaries
PHOBOS: Very preliminary data. (May ‘97)
Beam thru hole: 50k pions @ 5GeV
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JUNE 1997 PHOBOS Review Mark D. Baker
Measurement of secondaries
PHOBOS: Very preliminarydata! (May ‘97)
Fe target No target
Beam hits detector:
Beam thru hole:
5 GeV beam:
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JUNE 1997 PHOBOS 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.
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JUNE 1997 PHOBOS Review Mark D. Baker
Hough Tracking Event Display
Placeholder only. Will use baker_sideways.ppt
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JUNE 1997 PHOBOS 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
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JUNE 1997 PHOBOS Review Mark D. Baker
Momentum Resolution
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JUNE 1997 PHOBOS Review Mark D. Baker
Tracking vs. Plane Efficiency
• No major problem– 1% plane inefficiency 2% tracking inefficiency
– Probably improvable (better covariance matrices)
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JUNE 1997 PHOBOS Review Mark D. Baker
Track finding - very low Pt
deg
deg
deg
deg
7 planes, E>800 keV
7 planes, all hits
80
6020 40
20 40 60
80
0
0
-8
8
8
-8
Stopping Kaon
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JUNE 1997 PHOBOS Review Mark D. Baker
Particle ID by dE/dx
safe extended
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JUNE 1997 PHOBOS Review Mark D. Baker
Particle ID - very low Pt
2
1
dx
dE
2mEkin
mdx
dEEkin
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JUNE 1997 PHOBOS Review Mark D. Baker
Particle ID - very low Ptm
ass
para
met
er
mas
s pa
ram
eter
)(MeVEloss )(MeVEloss
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JUNE 1997 PHOBOS Review Mark D. Baker
Spectrometer Acceptance
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JUNE 1997 PHOBOS Review Mark D. Baker
HBT Acceptance
TruthResolution smeared
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JUNE 1997 PHOBOS Review Mark D. Baker
PHOBOS HBT Capabilities
• “Standard” Scenario– Extrapolate from low E
• Exotic Scenario I– Very large source
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JUNE 1997 PHOBOS Review Mark D. Baker
PHOBOS HBT Capabilities• “Standard” Scenario
– Extrapolate from low E
• Exotic Scenario II– Very rapid expansion
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JUNE 1997 PHOBOS 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.
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JUNE 1997 PHOBOS 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
+
+
+
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JUNE 1997 PHOBOS 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)
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JUNE 1997 PHOBOS Review Mark D. Baker
Phi Width Measurement
Placeholder only
see baker_sideways.ppt
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JUNE 1997 PHOBOS Review Mark D. Baker
Phi Width Measurement
Placeholder only
see baker_sideways.ppt
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JUNE 1997 PHOBOS Review Mark D. Baker
Computing Organization
R . V erd ie rD ep u ty H ead
D . M cL eodC . C on n er
C . H a lliwe llO n lin e M on ito rin g
A . Trzu p ekP ID & low P t
P . D ecow sk i B . W os iekm om . fit t in g
G . R o lan dS p ec t. R econ s tru c tion
R . G an zP rim ary V ertex
R . V erd ie rM u ltip lic ity R econ .
R . G an zTes tb eam A n a lys is
K . W ozn iakG E A N T M C
A . O lszewsk iF as t S im .
A . Trzu p ekG eom etry
E .G arc ia -S o lisG en era to rs
B . W os iekS im u la tion s & K rakow L iason
A . O lszewsk iP . D ecow sk i
TB A : (V erd ie r/R o lan d /G an z )O fflin e In fras tru c tu re
M . B akerH ead o f C om p u tin g ~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
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JUNE 1997 PHOBOS 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 acceptanceT