heavy quark probes of qcd matter at rhic huan zhong huang university of california at los angeles...
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Heavy Quark Probes of QCD Matter at RHIC
Huan Zhong Huang
University of California at Los Angeles
ICHEP-2004
Beijing, 2004
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Outline
1) Experimental Evidences for Bulk MatterHadronization
2) Recombination for Heavy Quark Mesons
3) Future Measurements of Heavy QuarkProduction Features at RHIC
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Too Many Baryons at Intermediate pT
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Baryon Production from pQCD
K Kp p
e+e-jet fragmentation from SLD
Normal Fragmentation Cannot Produce the Large Baryon Yield
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Nuclear Modification Factors
ddp
Nd
collddpNd
TAA
T
pp
T
AA NpR 2
2
/)(
Use number of binary nucleon-nucleon collisions to gauge the colliding parton flux:
N-binary Scaling RAA or RCP = 1 simple superposition of independent nucleon-nucleon collisions !
Peripheralcoll
T
Centralcoll
TTCP
NddpNd
NddpNd
pR
]/[
]/[
)( 2
2
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Particle Dependence of RCP
suppression
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STAR
PHENIX
Particle Dependence of v2
Baryon
Meson
Why saturation at intermediate pT ?Why baryon and meson difference ?
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Salient Features at Inermediate pT
1)Why so many baryons versus mesons?
2)Why does elliptic v2 versus pT saturate ?
3)Why Rcp and v2 in two groups: Baryon and Meson ?
Hadronization from bulk partonic matter – Constituent quark degrees of freedom Recombination/Coalescence scheme for hadron formation Surface emission
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Constituent Quark Degree of Freedom
KS – two quark coalescence– three quark coalescence from the partonic matter surface?!
Particle v2 may be related to quark matter anisotropy !!
pT < 1 GeV/c may be affected by hydrodynamic flow !
Hadronization Scheme for Bulk Partonic Matter:
Quark Coalescence – (ALCOR-J.Zimanyi et al, AMPT-Lin et al, Rafelski+Danos, Molnar+Voloshin …..)
Quark Recombination – (R.J. Fries et al, R. Hwa et al)
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Quark Cluster Formation from Strongly Interacting Partonic Matter
Volcanic mediate pT – Spatter (clumps)
Strangeness enhancement from QGP is most prominent in the region where particle formation from quark coalescence is dominant !
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Multi-Parton Dynamics for Bulk Matter Hadronization
Essential difference:Traditional fragmentation particle properties mostly determined by the leading quark !Emerging picture from RHIC data (RAA/RCP and v2) all
constituent quarks are almost equally important in determining particle properties !
v2 of hadron comes from v2 of all constituent quarks !
Are constituent quarks the effective degrees of freedom for bulk partonic matter hadronization ? How do we establish signatures for multi-parton dynamics, recombination model for example, where thermal constituent quarks or shower partons from jet production are both possible ?
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Fragmentation vs RecombinationFragmentation Function z = phadron/pparton < 1
Recombination Scheme phadron = pparton-1 + pparton-2 … Z >= 1
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Fragmentation Functions from e+e Collisions
Belle Data
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Charm Mesons from Hadronic Collisions
Charm meson pT ~ follow the NLO charm quark pT
-- add kT kick -- harder fragmentation ( func or recombination scheme)
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kT Kick? What about kL?
The xF distribution matches the NLO charm quark xF !
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The RHIC D meson pT ~ NLO charm quark too
NLO pQCD predictions are provided by R. Vogt, hep-ph/0203151
STAR Preliminary
But NLO QCD calculation fits CDF data within a factor of 2
Recombination mechanism for D formation ?!
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Recombination DS/D0
PYTHIA Prediction
Charm quark recombines with a light (u,d,s) quark from a strangeness equilibrated partonic matter DS/D0 ~ 0.4-0.5 at intermediate pT !!!
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pT Scales and Physical Processes
RCPThree PT Regions:
-- Fragmentation
-- multi-parton dynamics (recombination or coalescence or …)
-- Hydrodynamics (constituent quarks ? parton dynamics from gluons to constituent quarks? )
PT scale for heavy quarks?
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Summary
Formation of Dense Matter
Partonic Degrees of Freedom Important Hadronization of Bulk Partonic Matter
Heavy Quark Measurement One of the Key Future Critical Test of Multi-parton Dynamics for Hadronization
Signature for Deconfinement !
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The End
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Two Particle Jet-like Correlations
Jet-like two particle correlations (e.g., trigger particle 4-6 GeV/c, associated particle 2-4 GeV/c) :
These correlations cannot be easily explained in terms of recombination/coalescence scenario !
But 1) the effect of resonances on the two particle correlations has not be adequately addressed 2) trigger biases – with two high pT particles the initial parton is considerably harder than if only one high pT particle
is produced. Fragmentation region pT > 5.5 GeV/c 3) low level two particle correlations in the soft region can be
accommodated in recombination/coalescence(wave induced correlation?)
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Heavy Quark in QCD Medium
• Heavy Quark energy loss in color medium !
-- dead cone effect (less than light quarks)• Charm enhancement from high temperature
gluonic matter (Tinit > 500 MeV)!
An Intriguing Scenario ?!
PT
RAA
1.0
Light hadrons
Open Charm
(pT scale)
Require direct open charm measurement !
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Geometry of Nucleus-Nucleus Collisions
Number of Participants
Impact Parameter
Npart – No of participant nucleonsNbinary – No of binary nucleon-nucleon collisions cannot be directly measured at RHIC estimated from Woods-Saxon geometry
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A Critical Test for Recombination
Duke Group, PLB 587, 73 (2004)
pT Scale !!
And Strange Quark Dynamics in Bulk Matter
STAR will make a measurement of and v2 from run-4 Au+Au data !
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Elliptic Flow Parameter v2
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Initial/final conditions, dof, EOS
1i
Ritttt
))ψcos(i(2v1dydpp
dN
2π
1
dyddpp
dN
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The The Field & FeynmanField & Feynman picture of cascade fragmentation picture of cascade fragmentation
Kretzer@ISMD04
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Charm and Bulk Matter
Does Charm Flow?Thermalization of partonic matter -- charm elliptic flow v2 ! -- charm hadron chemistry !
Simulation by X. Dong
Charm Meson v2 has to come from light quark v2
and possibly charm quark v2 !