Electron Flow in AuAu@200GeV

1

Electron Flow in AuAu@200GeV

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

200GeV (old) Au+Au

minimum bias trigger

Frank Laue([email protected])

for

the STAR Collaboration

Hot Quarks 2004 Frank Laue, BNL ([email protected]) 2

Motivators

•All mesons behave the same

•All baryons behave the same

•Mesons behave differently from baryons

Kai Schweda

STAR QM2004

•NCQ scaling

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


Motivators

Fries,Mueller,Nonaka,Bass

nucl-th/0308051

•NCQ scaling doesn’t work everywhere ?

•v2 is very sensitive probe


Questions/Problems •Data suggests NCQ scaling (coalescence,recombination) 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, shouldn’t 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


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 ! e+e- + B.R.

1.198%)• detector effects ( ! e+e- : few %, dep. on

material)


Do Decay-Electrons Reflect the Parent Flow ?Electron vs D Momenta

pelectron (GeV/c) pelectron (GeV/c)

pD

-Meso

n (

GeV

/c)

pD

-Meso

n (

GeV

/c)

Hot Quarks 2004 Frank Laue, BNL ([email protected]) 7pelectron (GeV/c) pD-Meson (GeV/c)

D-

Ele

ctro

n

D-

Ele

ctro

n

Do Decay-Electrons Reflect the Parent Flow ? vs D Momenta


Do Decay-Electrons Reflect the Parent Flow ?Pythia/Mevsim Simulation

pT / (GeV/c) pT / (GeV/c)

v2 %

v2 %

•D0 (input)

oe§

• 0 (input)

oe§


Where Do The Electron Come From ?(Pythia)

pelectron (GeV/c)

Fraction of electrons from:

• 0 ! e+ + e- +

•D ! e§ + X

F

pelectron (GeV/c)

d2N

/(d

pdy)

(a

.u.)


Where Do The Electron Come From ?(Pythia, STAR Simulation/Analysis Chain)

Pythia 6.2

Heavy Quarks turned on

GStar

Reconstruction

Track Associations

| eta | < 1

DCA < 2cm

23 < #fit-Points < 100

20 < #dEdx-Points < 100

0

K0L

,

K0

D0,D§


TPC dE/dx vs p

log10(p/(GeV/c)

dE/d

x/(

KeV

) +

dE/d

x/(

KeV

)

log10(p/(GeV/c)

-

e+


Electron Selection• “clean” electrons between the blue lines

• conversion removed via invariant mass method (~50% efficiency)


Deuteron Contamination (preliminary)

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

• 2x as many deuterons and anti-deuterons

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

p/(GeV/c)

raw

-yie

ld

dE/d

x/

(KeV

)

log10(p/(GeV/c)

- <20% contam


-conversions and 0-Dalitz Decays

pT/(GeV/c)v 2

%

mass/(GeV/c2)

dN/d

mas

s 0 ! e+ + e- +

~50-80% of ’s can be removed with invariant mass method


V2 vs pT

cos(2(-))

pT/(

GeV

/c)

pT/(GeV/c)

black = electrons+positrons

electrons

positrons


PHENIX PRELIMINARY

STAR Preliminary

Flow of electrons (charm): v2 from PHENIX & STAR

Slightly different dE/dx cut:

3.4<dE/dx<5.0

Au+Au @200GeV

•Run II

•Run IV (fast offline)


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 100m Vertex Resolution)• (almost) background free identification of D/B-Mesons


Yields vs (phi-psi)

black = electrons red = fit to electrons blue = hadrons


Electron v2

all chargeselectrons

positrons

Electron Flow in AuAu@200GeV

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