Cold Nuclear Matter Effects on Open Heavy Flavor at RHIC
J. Matthew Durhamfor the PHENIX CollaborationStony Brook University
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Open Heavy Flavor at RHIC
Phys. Rev. Lett. 98, 172301 (2007)
One of the most striking results from RHIC is the strong suppression and flow of heavy quarks in Au+Au collisions
d+Au
Au+Au
d+Au allows quantification of nuclear effects without complications of hot medium
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Cold Nuclear Matter Effects
Phys. Rev. C 74, 024904 (2006)
Mass ordering of Cronin enhancement observed for π,K,p
Does this continue with D meson? B?
MD ~1.8 GeV
Closed heavy flavor is suppressed at mid-rapidity (details in Alex’s talk next)
Open heavy flavor in d+Au can shed light on these interesting phenomena
arXiv:1010.1246
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Measurement Methodology
Direct Reconstruction:
Identify parent meson via
daughter products
Indirect Method:
Measure leptons from D/B decays
Straightforward triggering scheme
PHENIX is especially well suited for lepton measurements
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The PHENIX Experiment Electrons are tracked by
drift chamber and pad chamber
The Ring Imaging Cherenkov Counter is primary electron ID device
Electromagnetic calorimeters measure electron energy – allow E/p comparisons
BBC/ZDC provide MinBias trigger and centrality determination in HI collisions
e+e
Run-8 Configuration
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Electron Sources Dalitz decays
Mostly Also from
Conversions in material Photons predominantly from
Kaon decays
Dielectron decays of vector mesons
Thermal/direct radiation Small but significant at high pt
Heavy Flavor Decays
ee 0
,,,
0
eeK 0
ee ,,
SIGNAL
BACKGROUND
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Background Subtraction Methods Cocktail Method
PHENIX has measurements of most of the background electron sources.
A cocktail of these sources are subtracted from the inclusive electron sample to isolate the HF contribution.
Converter Method Extra material in the PHENIX
aperture intentionally increases background by a well defined amount.
Allows precise quantification of photonic background.
arXiv:1005.3674
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Conversions Vast majority of conversion electrons come from photons
from , with kinematics very similar to Scale up Dalitz decay electrons by appropriate factor to
account for conversions (determined through simulation)
Cocktail Ingredients I Light mesons
Fit d+Au pion data with Hagedorn function Set other meson’s shape with mt-scaling Normalization set by particle ratios at high pt
2220mMpmp mesonttt
0 ee 0 0 ee 0
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Cocktail Ingredients II Direct Photons
PHENIX p+p data, scaled up by Ncoll for each centrality
Ke3 decays Electrons from kaon decays away from the vertex are
mis-reconstructed at high pT.
Full simulation of PHENIX detector determines Ke3 contribution (only relevant at pT<1GeV/c)
A note on the J/ψ: We know J/ ψ is suppressed in d+Au We don’t yet have kinematic dependence of J/ ψ RdA
J/ ψ is significant at high pT, so knowledge of the exact behavior at pT>4GeV/c is necessary to correctly account for this contribution
As of now, J/ ψ is not subtracted
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Total MB Cocktail
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Converter Method
noninconv
nonoutconv
NNRN
NNN
)1(
For one day in Run-8, a brass sheet was wrapped around the beam pipe.
This increases photonic background by a well defined amount.
Precise measurements of converter material allow precise determination of Rγ via simulation
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Cocktail and Converter Comparison
1
)1(
R
NNN
outconvinconv
Cocktail method gives a calculation of photonic background
Converter method gives us a measurement of photonic background
Difference is ~10% for all centralities.
Photonic cocktail components scaled to match converter data.
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Photonic Backgrounds
Excellent agreement between the two methods
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Heavy Flavor Electron Spectra
Subtract cocktail from the inclusive electron sample to obtain the HF contribution
Black line is Ncoll scaled fit to p+p
With d+Au spectra, divide by scaled p+p reference to obtain RdA
ppT
eHFcoll
AudT
eHF
dAu
dpdNN
dpdN
R
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Peripheral RdA
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Semi-Peripheral RdA
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Semi-Central RdA
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Central RdA
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Minimum Bias RdA
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Peripheral RdA consistent with p+p
Enhancement in open HF yields at 1<pT<4 GeV/c for more central collisions
Suppression at the highest pT
Rcp allows examination of “turn-on” of these effects within d+Au (with much smaller systematics) Aud
T
eHF
coll
AudT
eHF
collcp
dpdN
N
dpdN
NR
8860
8860
200
200
1
1
A few comments on RdA
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Rcp (40-60)/(60-88)
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Rcp (20-40)/(60-88)
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Rcp (0-20)/(60-88)
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Light Quarks Heavy Quarks
Phys. Rev. Lett. 101, 232301 (2008) arXiv:1005.1627
Phys. Rev. Lett. 98, 172302 (2007)
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At pT> 4 GeV/c:
AAAA RRe 0
dAdA RRe 0
At pT< 4 GeV/c:
AAAA RRe 0
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Summary PHENIX now has a full suite of heavy flavor
measurements across a wide range of Ncoll and colliding systems.
The Run-8 d+Au data set shows: Enhancement of open HF at moderate pT Suppression at the highest pT
This new reference for A+A data suggests heavy quark energy loss in the medium is even greater than previously thought:
Is the apparent difference in energy loss for light and heavy quarks really just a CNM effect?
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BACKUPS
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A. Dion, QM09
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Centrality Determination in d+Au
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Heavy Flavor Electron Spectra
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Heavy Flavor Electron Spectra
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Heavy Flavor Electron Spectra
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Heavy Flavor Electron Spectra
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