Electron Flow in AuAu200GeV

1
Electron Flow in AuAu_at_200GeV
Frank Laue(laue_at_bnl.gov) for the STAR
Collaboration

• Outline
• Motivation
• Analysis
• (Preliminary) Results
• Outlook

200GeV (old) AuAu minimum bias trigger
2
Motivators
Kai Schweda STAR QM2004

• All mesons behave the same
• All baryons behave the same
• Mesons behave differently from baryons

• NCQ scaling
• dynamic governed by partonic phase, which is
  observed after coalescence/recombination of
  quarks ?

3
Motivators
Fries,Mueller,Nonaka,Bass nucl-th/0308051

• NCQ scaling doesnt work everywhere ?
• v2 is very sensitive probe

4
Questions/Problems

• Data suggests NCQ scaling (coalescence,recombinati
  on) for Elliptic Flow and RCP ! Partonic Phase
  (hey, ho the QGP!)
• What about hydro-dynamics ? (governed by mass,
  not NCQ)
• successful spectra (Tkin,?f), Nu Xu plot (Teff
  vs mass) ! radial flow
• Radial / Elliptic Flow both caused but pressure,
  shouldnt they scale similarly ?
• Why does NCQ scaling works so good at higher pT
  (phasespace scarcely populated, coalescence less
  likely)
• s(trongly interacting)QGP, parton-hydrodynamics ?
• u,d¼ 5MeV s¼150MeV, c¼1.5GeV
• ! look at charm, both in partonic and hadronic
  world the charm is very heavy should be very
  sensitive

5
Line of Thought

• Can not measure Charm-Flow directly (yet)
• Do D-Meson decay electrons reflect the D-Meson
  flow ?
• Electron Identification
• Where do the Electrons come from ?
• Backgrounds from
• misidentification (contamination)
• physics processes (?0 ! ee- ? B.R. 1.198)
• detector effects ( ?! ee- few , dep. on
  material)

6
Do Decay-Electrons Reflect the Parent Flow
?Electron vs D Momenta
pD-Meson (GeV/c)
pD-Meson (GeV/c)
pelectron (GeV/c)
pelectron (GeV/c)
7
Do Decay-Electrons Reflect the Parent Flow ???
vs D Momenta
?D-?Electron
?D-?Electron
pD-Meson (GeV/c)
pelectron (GeV/c)
8
Do Decay-Electrons Reflect the Parent Flow
?Pythia/Mevsim Simulation

• ?0 (input)
• e

v2
v2

• D0 (input)
• e

pT / (GeV/c)
pT / (GeV/c)
9
Where Do The Electron Come From ?(Pythia)
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Where Do The Electron Come From ?(Pythia, STAR
Simulation/Analysis Chain)
Pythia 6.2 Heavy Quarks turned on GStar Reconstruc
tion Track Associations
?
?0
?,?
D0,D
eta dEdx-Points K0L
K0
11
TPC dE/dx vs p
e
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Electron Selection

• clean electrons between the blue lines
• ? conversion removed via invariant mass method
  (50 efficiency)

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Deuteron Contamination (preliminary)
raw-yield
p/(GeV/c)

• 2x as many deuterons and anti-deuterons
• 2x(3) more electrons(positrons) than extrapolated
  (anti-)deuterons

• more than ½ of (anti-)deuterons out of dEdx band

14
?-conversions and ?0-Dalitz Decays
?0 ! e e- ?
?
50-80 of ?s can be removed with invariant mass
method
15
V2 vs pT
pT/(GeV/c)
cos(2(?-?))
pT/(GeV/c)
16
Flow of electrons (charm) v2 from PHENIX STAR
Slightly different dE/dx cut 3.4

AuAu _at_200GeV

Run II

Run IV (fast offline)

17
Outlook / To-Do-List

• Quantitative measurements
• contaminations and background (yields)
• measure flow of contam./ background
• ! non-photonic v2
• deuteron flow (constituent model)
• 100x better statistics in Run IV (already on
  tape)
• centrality dependence
• reduce backgrounds by 80 with tighter cuts
• EMC electron analysis is already prepared
• too low statistics for 62GeV
• higher pT , bkg reduction
• Pixel Vertex Detector (¼ 100?m Vertex Resolution)
• (almost) background free identification of
  D/B-Mesons

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Yields vs (phi-psi)
black electrons red fit to electrons
blue hadrons
19
Electron v2
all charges
electrons positrons