Hot Quarks 2004

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Electrons (and Electron Pairs) in STAR

• Charm (onium) and Bottom (onium!) in STAR

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Heavy Flavor Program In STAR

• Learn about charm/beauty physics (Peter and Matt)
• Suppression? Potential for direct probe of
  deconfinement?
• Very long term quarkonium spectroscopy
• Measurements
• Open Charm via Ds H. Zhang (yesterday)
• Single electrons Access charm (and bottom at
  higher pt!)
• ee- pairsQuarkonium J/Y, ?
• Electron ID capabilites
• Single electron data
• TPCEMC
• Electron pairs towards quarkonium
• Run IV data

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Electron Identification, dE/dx

• Use TPC for dE/dx
• Look at pgt1.5 GeV/c
• Can see a region where the electron band sits.
• Not ideal, but
• LARGE acceptance
• h?1, 0ltflt2p
• TOF in limited f

4
Electron Identification dE/dx

• Can select two regions
• around electron band
• signal
• Outside electron band
• Background
• e/h 500 (p dependent)

5
Electron Identification, Barrel EMC

• Run IV acc
• 0lthlt1, 0ltflt2p
• Distance from track to center of a tower
• Tower Energy
• High-granularity Shower Maximum information

6
Barrel EMC Electron ID

• p/E for electron and hadron candidates
• p is the track momentum, E is the tower energy
• Peak position depends on the distance to the
  center of the tower
• EMC e/h 250
• (pT-dependent)
• Combined EMCTPC e/h105

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High-pT electron trigger

• EMC provides a Level 0 high-pT electron trigger
• Runs for every RHIC crossing (10 MHz)
• Two ET thresholds
• 2.5 and 5 GeV
• Enhancement as high as 1000 for pT gt 5 GeV/c

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Deconstructing the spectrum

• Total electron spectra
• Background
• Instrumental sources
• ? convertion
• Hadron background
• Dalitz decays (p0, ?)
• Kaon decays
• vector meson decays (? ? F)
• Signal
• heavy quark semi-leptonic decay
• Drell-Yan, Thermal, etc

9
Background finding efficiency

• Need knowledge of background finding efficiency
  vs. p
• Shape of p0 spectrum
• Measure most of the background (avoids cocktail)

10
Inclusive spectrum
Preliminary

• Awaiting final reproduction of dAu data

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Non-Photonic spectrum

• EMC TOF analysis agree
• Can calculate e from Open Charm
• Charm could be dominant source below 4-5 GeV/c

Preliminary
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RdAu

• Also see Cronin for e in dAu (Cronin for charm)

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Bottom?

• PYTHIA 6.22
• width of primordial kT distribution 1.5 GeV/c
• mc 1.25 GeV/c2, mb 4.8/5.0 GeV/c2
• K-factor ? obtain from fit
• Definition in 2?2 hard parton scattering Q2s
• HF production MSEL 4
• parton virtuality PARP(67) 1
  
• PDF CTEQ5L, GRV 94D
• Vary parameters
• for each parameter set fit measured spectrum with
  either common or separate K factor for c and b
  components
• Match measured scc
• Extract?bb cross-section
• sbb rather stable against variation
• sbb ? 5 mb

In Progress
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Electron Pairs Quarkonium Trigger

• Divide f in 6 sections
• Find a tower above a threshold
• Look in the 3 opposite sections in f
• If another tower above threshold, trigger!

15
AuAu Production Rates

• (BR x s) in pp _at_ ?s200 GeV
• Rates per event, into ee-, per unit y at y0

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So, How many in Run IV?
? Yield 0.02 ? ? ee-, pgt3 GeV per 1M min-bias
events 0.1 ? ? ee-, pgt3 GeV per 1M 10 central
events (Triggered event central)
J/y Yield 12 J/y ? ee-, pgt1.2 GeV per 1M
min-bias events 50 J/y ? ee-, pgt1.2 GeV per
1M 10 central events

• Run IV
• Min bias
• 30M 12x30 360
• Central
• 50x30 1500

Include - fAB (hard fraction) - 1 unit ? 4p -
Acceptance (1/2 Barrel) Assuming 0.5x(3/4
Barrel) - momentum cut
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Did the trigger work?
minimum bias 7854 events Central 26581 Upsilon
triggers 1159
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Summary

• BEMC analysis electrons in STAR is on shell!
• Single electron results in pp, dAu soon to be
  finalized
• E seem to show Cronin
• Beauty starts to dominate 4-5 GeV/c (model dep.)
• sbb 5mb
• Electron pairs can be accessed in STAR
• Trigger on J/Y in pp offline search in AuAu Run
  IV
• Trigger on ? in all systems caveat small s
• Getting ready for the production of Run IV data
• For theorists in the house predictions!

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Trigger Bias

• Sufficient overlap between minimum bias and EMC
  triggered data
• Can combine all 3 datasets