Post on 21-Jan-2016
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