Open charm production at RHIC
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Transcript of Open charm production at RHIC
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1Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Open charm production at RHIC
Xin DongUniversity of Science and Technology of China - USTC
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2Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Outline
Introduction
Charm in elementary collisions
Open charm production in heavy ion collisions Total charm yields
Charm quark ΔE in medium
Charm quark v2
Summary and outlook
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3Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
What we have learned at RHIC
pT (GeV/c)0
~2 ~6
Jet quenchingpQCD at work, high density matter
Hydro at workstrong interactionscollectivity
NCQ groupingpartonic d.o.f
Jet-quenching: high density medium created Large v2 and βT: partonic collectivity NCQ-grouping: partonic collectivity and deconfinement
To fix the partonic EOS, one must test the thermalization experimentally.
Heavy flavor probe:Heavy flavor collectivity → light flavor thermalization Note: to test the bulk medium response, low pT region is relevant!
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4Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Why Charm? – an ideal probe for studying QGP
B. Mueller, nucl-th/0404015
Heavy ! Charm quarks created at
early stage of HIC
total yields scaled by Nbin
Sensitive to the partonic
rescatterings Collectivity, flow
light flavor thermalization
Charm as a probe to test early thermalization!
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5Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Charm energy loss
k
E
M
dP
k
dkkdCdP Fs
,
)/1()(
0
2220
022
022
22
Y. Dokshitzer & D. Kharzeev PLB 519(2001)199
Radiative energy loss of heavy quarks and light quarks
--- Probe the medium property !
Heavy quark has less dE/dx due to suppression of small angle gluon radiation
“Dead Cone” effect
M. Djordjevic, et. al. PRL 94(2005)112301
B.W. Zhang et. al. PRL 93(2004)072301
N. Armesto et. al. PRD71(2005)054027
R. Rapp et. al. ……
J. Adams et. al, PRL 91(2003)072304
h±
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6Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Charm elliptic flow
V. Greco et al., PLB 595(2004)202
Coalescence approach
Large cross section needed to reach high v2 : Charm quark flows → Indication of light flavor thermal equilibrium! Is the large cross section realistic?
AMPT transport model
B. Zhang et al., nucl-th/0502056
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7Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
The key point is to determine
Charm collectivity
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8Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Charm measurements at RHIC
central arms --- electrons: DC (tracker), Ring Image Cherenkov (RICH), EMCal for(back)ward muon arms --- muons: muon tracker, muon identifier
D recon. from hadronic decay channels: TPC (+TOF) electrons: TPC, TPC+TOF, TPC+EMC
Advantages: -- low material budget, clean environ. -- central, forward/backward coverage
Advantages: -- reconstruction of D mesons -- large acceptance |φ|<2π,|η|<1.5
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9Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
R. Vogt Int. J. Mod. Phys. E 12(2003)211
D mesons
, ’,
Large Q value needed (>≈3GeV)
powerful test for pQCD calculation
Heavy flavor in pQCD
PDFccbar pQCD
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10Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
%)8.3(%),68( 00* KDDD s %)8.3(0 KD
Direct charm reconstruction
STAR Preliminary
STAR, PRL, 94, 062301 (2005)
d+Au 200 GeV
STAR: Mixed-event technique benefiting from large acceptance of the TPC
A. Tai, QM04
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11Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Non-photonic electrons
PHENIX: three methods to subtract the photonic background
S. Kelly, QM04
STAR: three independent analysis using different sub-detectors
EMC -- STAR preliminary
σcc = 1.4 0.2 0.4 mbSTAR, PRL, 94, 062301 (2005)
p+p 200 GeV
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12Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Issue I - total charm cross section
1) STAR > pQCD PHENIX >~ pQCD
2) Charm total cross section is a critical reference for J/ψ suppression/enhancement determination.
3) Scales (μF and μR ) may be energy dependent.
STAR, PRL, 94, 062301 (2005)
R. Vogt, private communication
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13Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Spectrum coverage
σcc = 1.1 0.1 0.3 mb
The reconstructed D measurement has much smaller systematic uncertainties in determining the total cross section.
<pT> ~ 1.3 GeV/c
90%
15%
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14Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Issue II - pT spectrum
PYTHIA spectrum is steeper than data spectrum beauty contamination:Typical pQCD calculations: Beauty will take over charm beyond ~4 GeV/c M. Cacciari et. al. hep-ph/0502203
PYTHIA curves from S. Kelly, QM04
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15Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Summary on charm in elementary collisions
Open issues of charm production in elementary collisions:
Total charm cross section is higher than typical pQCD calculations!
Spectrum is harder than those from typical PYTHIA predictions!
Beauty contribution
Precise measurements of reconstructed open charm in elementary collisions are definitely necessary!
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16Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Centrality dependence of non-photonic electrons in Au + Au
PHENIX, PRL 94, 082301(2005)
Centrality dependence of charm production is consistent with Nbin scaling at 0.8<pT(e)<4.0 GeV/c!
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17Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
d + Au Au + Au
STAR Highlight talk
1.13 0.09 0.42 mb in Au + Au
1.4 0.2 0.4 mb in d + Au
Approximately Nbin scaling from d+Au to Au+Au!
As expected --- charm quarks are mostly created from initial NN interactions!
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(3) q_hat = 14 GeV2/fm
(2) q_hat = 4 GeV2/fm
(1) q_hat = 0 GeV2/fm
(4) dNg / dy = 1000
RAA of non-photonic electrons
PHENIX Highlight talk
Both experiments agree! Clear evidence of large heavy quark energy loss!
STAR Highlight talk
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19Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Challenges to theoretical friends
M. Djordjevic, et. al. nucl-th/0507019 N. Armesto et. al. private comm.
Current energy loss mechanisms can only account for part of strong suppression of RAA for electrons.
any beauty?
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20Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Charm quark collective motion
Electron spectra cannot disentangle different charm hadron shapes at low pT
→ Need precise measurement of reconstructed D at low pT (<~3GeV/c)!
S. Batsouli, et al, Phys.Lett.B 557 (2003) 26 Electrons: Smearing in pT axis
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21Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
V. Greco et al.PLB 595(2004)202
Non-photonic electron v2
Experimental data do not agree at 2<pT(e)<5 GeV/c! v2(e) favors non-zero v2(c) at pT(e)<2 GeV/c.
B. Zhang et al.nucl-th/0502056
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22Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Summary
Charm production cross section at 200 GeV measured in
elementary collisions. Total charm yields in HIC approximately obey Nbin scaling.
v2(e) favors non-zero v2(c) !?
RAA(e) ≈ RAA(h) !?
An exciting heavy flavor program has started at RHIC!
Open Issues: pQCD description where is beauty?
Heavy flavor collectivity!
Light flavor thermalization!@RHIC
If confirmed
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23Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Summary
Before any physics conclusion, experimental data must agree! Single electron approaches are placeholder. Identified open charm (beauty) measurements are definitely
necessary. The upgrade programs in PHENIX and STAR are essential!
Electron approach experiences: 1) spectrum low pT: no distinguishing power high pT: beauty is largely uncertain 2) v2
large statistical and systematical uncertainties
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24Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Upgrade detectors at PHENIX
Barrel and Endcap Silicon Vertex Tracker
Direct charm/beauty reconstruction: low pT via e/μ, high pT via Kπ
G. Kunde, WW 05
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25Aug. 4-9, 2005, QM2005, Budapest X.Dong, USTC
Upgrade detectors at STAR
Full Barrel MRPC - TOF Heavy Flavor Tracker
Full open charm measurements - direct D-meson V0 reconstruction - spectrum, v2 (low high pT), correlations …
K. Schweda’s talk