heavy quark probes of qcd matter at rhic huan zhong huang university of california at los angeles...
TRANSCRIPT
Heavy Quark Probes of QCD Matter at RHIC
Huan Zhong Huang
University of California at Los Angeles
ICHEP-2004
Beijing, 2004
Outline
1) Experimental Evidences for Bulk MatterHadronization
2) Recombination for Heavy Quark Mesons
3) Future Measurements of Heavy QuarkProduction Features at RHIC
Too Many Baryons at Intermediate pT
Baryon Production from pQCD
K Kp p
e+e-jet fragmentation from SLD
Normal Fragmentation Cannot Produce the Large Baryon Yield
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
Particle Dependence of RCP
suppression
STAR
PHENIX
Particle Dependence of v2
Baryon
Meson
Why saturation at intermediate pT ?Why baryon and meson difference ?
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
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)
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 !
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 ?
Fragmentation vs RecombinationFragmentation Function z = phadron/pparton < 1
Recombination Scheme phadron = pparton-1 + pparton-2 … Z >= 1
Fragmentation Functions from e+e Collisions
Belle Data
Charm Mesons from Hadronic Collisions
Charm meson pT ~ follow the NLO charm quark pT
-- add kT kick -- harder fragmentation ( func or recombination scheme)
kT Kick? What about kL?
The xF distribution matches the NLO charm quark xF !
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 ?!
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 !!!
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?
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 !
The End
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?)
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 !
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
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 !
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
The The Field & FeynmanField & Feynman picture of cascade fragmentation picture of cascade fragmentation
Kretzer@ISMD04
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 !