Ralf AverbeckStony Brook University

Hot Quarks 2004Taos, New Mexico, July 19-24, 2004

for the Collaboration

Open Heavy Flavor Measurementswith PHENIX at RHIC

R. Averbeck, Stony Brook,2Hot Quarks 7/22/2004

Outline Why is open charm (and beauty) interesting? How can charm be measured? The PHENIX experiment at RHIC Open charm studies with PHENIX

Past– e± from charm in AuAu @ √sNN = 130 GeV

(pioneering measurement at RHIC) Present

– e± from charm in pp @ √s = 200 GeV (providing the reference)

– e± from charm in dAu and AuAu @ √sNN = 200 GeV (systematic study)

Future– near term (analysis of RHIC Run-4/5 data)– in the distance

Conclusions

R. Averbeck, Stony Brook,3Hot Quarks 7/22/2004

production of heavy quark-antiquark pairs dominated by gluon-gluon hard scattering

– sensitive to initial gluon density– sensitive to gluon spin

additional thermal production enhancement?– sensitive to initial temperature

propagation through dense medium energy loss by gluon radiation and/or thermalization

softening of spectra and/or flow?– sensitive to properties of the produced nuclear medium

does charm flow?– sensitive to collectivity on parton level

systematic study of charm yield & spectra is of prime importance!

baseline for quarkonia studies (DongJo Kim’s talk)

Why is open charm interesting?

R. Averbeck, Stony Brook,4Hot Quarks 7/22/2004

ideal (but challenging) direct reconstruction of charm decays (e.g. ) much easier if displaced vertex is measured

(PHENIX upgrade) alternative (but indirect)

contribution of semi leptonic charm decays to– single lepton spectra– lepton-pair spectra

How can charm be measured?

D0 K- +

c c

0DK

0D

K

0eD K

0D K

0 0e eD D e e K K

0 0eD D e K K

0 0D D K K

R. Averbeck, Stony Brook,5Hot Quarks 7/22/2004

PHENIX @ RHIConly RHIC experiment

optimized for lepton measurements

two forward muon spectrometers

muons: forward arms muon measurement

in range: 1.2 < || < 2.4 p 2 GeV/c

electrons: central arms electron measurement

in range: 0.35 p 0.2 GeV/c

two central electron/photon/hadron spectrometers

R. Averbeck, Stony Brook,6Hot Quarks 7/22/2004

compare excess with PYTHIA calculation

pp scaled to AuAu with Ncoll reasonable agreement

PYTHIA

direct (J. Alam et al. PRC 63(2001)021901)

b

c

First charm “measurement” in HI collisions

PHENIX: PRL 88(2002)192303

conversion

0 ee

ee, 30

ee, 0ee

ee, ee

ee

’ ee

0 92%cc 420 33 250 b

PHENIX: PRL 88(2002)192303

cocktail analysis of inclusive e± in AuAu @ √sNN=130 GeV

establish “cocktail” of e± sources (from data) light hadron decays photon conversions

excess above cocktail increases with pT attributed to charm decays

R. Averbeck, Stony Brook,7Hot Quarks 7/22/2004

From pioneering to systematic studies “executive summary” of pioneering AuAu measurement

uncertainties are LARGE charm in AuAu ≈ PYTHIA pp + binary collision scaling

NECESSARY improvements replace PYTHIA with pp MEASUREMENT as reference study centrality dependence in dAu & AuAu increase statistics: pp, dAu & AuAu @ √s = 200 GeV defeat main sys. uncertainty in cocktail analysis: conversion

– new method: “converter subtraction”– add thin converter (1.7 % X0) to experiment– comparison of e± spectra with & without converter

calibration of conversion contribution

2 methods: converter & cocktail converter “wins” at low pT yield measurement cocktail “wins” at high pT measurement of spectral shape

R. Averbeck, Stony Brook,8Hot Quarks 7/22/2004

PHENIX PRELIMINARY

The reference: pp @ 200 GeV non-photonic e± from pp

collisions at 200 GeV “standard” PYTHIA

parameterizations pT > 1.5 GeV/c: spectra

are “harder” than PYTHIA

PHENIX PRELIMINARY

reference for nuclear collisions spectral shape

– PYTHIA charm & bottom line shapes with normalization as free parameters

total cross section– PYTHIA describes data at low pT

– PYTHIA extrapolation to full phase space

R. Averbeck, Stony Brook,9Hot Quarks 7/22/2004

PHENIX PRELIMINARY

Cold nuclear matter: dAu @ 200 GeV non-photonic e± in

dAu at 200 GeV difference in system

size between pp and dAu

divide dAu cross section by nuclear overlap integral TAB

dAu ≈ scaled pp (within errors)

no indication for strong cold-nuclear matter effects

how about centrality dependence?

1/T

ABE

dN/d

p3 [m

b G

eV-2]

R. Averbeck, Stony Brook,10Hot Quarks 7/22/2004

Centrality (in)dependence in dAu

PHENIX PRELIMINARY

PHENIX PRELIMINARYPHENIX PRELIMINARY

PHENIX PRELIMINARY

1/T A

B1/

T AB

1/T A

B1/

T AB

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

R. Averbeck, Stony Brook,11Hot Quarks 7/22/2004

Hot nuclear matter: AuAu @ 200 GeV1/

TA

BE

dN/d

p3 [m

b G

eV-2]

PHENIX

non-photonic e± in AuAu at 200 GeV divide AuAu cross

section by nuclear overlap integral TAB

AuAu ≈ scaled pp (within errros) for pT ≤ 1.5 GeV/c

indication for high pT suppression? (large errors!)

how about centrality dependence?

R. Averbeck, Stony Brook,12Hot Quarks 7/22/2004

Centrality (in)dependence in AuAu

1/T A

A

1/T A

A

1/T A

A

1/T A

A

1/T A

A

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

1/T

ABE

dN/d

p3 [m

b G

eV-2]

starving for statistics at high pT!

R. Averbeck, Stony Brook,13Hot Quarks 7/22/2004

0.906 < < 1.042

charm yield seems to scale with TAB (or Ncoll)

dN/dy of e± in measured pT range tested for consistency with dN/dy = A(Ncoll)

90% C.L. on shown as yellow band

Binary collision scaling of yield in AuAu

binary scaling seems to work!

R. Averbeck, Stony Brook,14Hot Quarks 7/22/2004

Where to go from here? the obvious question:

modification of spectra in hot/dense medium? RAA vs. pT currently under investigation

continue systematic study of single e±

AuAu @ 62.4 GeV (Run-4) refine centrality dependence for AuAu @ 200 GeV

– Run-4 statistics ≈ 60 x Run-2 statistics– extend measurement of spectra to higher pT

(expect RAA ≈ 1 where beauty dominates the e± spectrum!)

– needs improved pp reference (Run-5)

single ± from heavy flavor in muon arms e+e- pairs from charm decays (next slide) PHENIX upgrade will provide new opportunities

vertex spectrometer to resolve displaced vertices D → K B → J/ K

R. Averbeck, Stony Brook,15Hot Quarks 7/22/2004

e+e- pairs from correlated charm decays dominant source of correlated e+e- pairs in mass range

between m and mJ/: charm decays

feasibility study for 200 GeV AuAu collisions (Run-2) huge combinatorial background

real and mixed e+e- distributions

background subtraction under control!

real - mixed = e+e- signal

starving for statistics Run-4 ≈ 60 x Run-2

R. Averbeck, Stony Brook,16Hot Quarks 7/22/2004

Summary PHENIX measurements at RHIC

inclusive e± in pp, dAu, and AuAu at √sNN = 200 GeV

yield of e± from non-photonic sources consistent with binary scaling no indication for strong enhancement / suppression

of charm cross section in nuclear collisions

e± spectra measured in pp are HARDER than expected from a PYTHIA calculation

statistics limited regarding presence of spectral modifications in Au+Au

(energy loss / thermalization)? charm flow in Au+Au? to be answered by currently ongoing Run-2/4

analyses