RHIC from Vacuum Engineering to Exotic Particle Factory

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RHIC from Vacuum Engineering to Exotic
Particle Factory

• Huan Zhong Huang (???)
• CUSPEA 84
• Department of Physics and Astronomy
• University of California Los Angeles
• Department of Engineering Physics
• Tsinghua University

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Outline

• Relativistic Heavy Ion Collider (RHIC) and
  Quark-Gluon Plasma (QGP)
• Formation of Dense Partonic Matter
• Hadronization of Bulk Partonic Matter
• Exotic Particle Factory
• Outlook

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Relativistic Heavy Ion Collider --- RHIC
AuAu 200 GeV N-N CM energy Polarized pp up to
500 GeV CM energy
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Quark-Hadron Phase Transition
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Vacuum Engineering-- The Melting of Quarks and
Gluons
Matter Compression Vacuum Heating
Deconfinement
High Temperature Vacuum -- high energy heavy
ion collisions -- the Big Bang
High Baryon Density -- low energy heavy ion
collisions -- neutron star?quark star
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Nucleus-Nucleus Collisions and Volcanic Eruption
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High pT Phenomena at RHIC
Very dense matter has been created in
central AuAu collisions! This dense matter is
responsible for the disappearance of
back-to-back correlation and the suppression of
high pT particles ! -- Jet Quenching!
Is the energy loss due to parton or hadron
stage? Is there a noticeable difference in
experimental phenomenon related to quarks
versus gluons? Is there a difference between
heavy quark and light quark energy loss in the
dense medium?
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Expectations for High pT from AuAu
Use number of binary nucleon-nucleon collisions
to gauge the colliding parton flux
N-Binary Scaling ? RAA 1
N-Binary Scaling works for very rare processes
i.g., Drell-Yan and direct photon
production with some caveats
(parton F2 and G change in A).
RAA can also be measured using central/peripheral
ratios !
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The Suppression is the Same for p0 and h parton
level effect
No suppression for direct photons
photons do not participate in strong interaction
with medium!
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No Significant Difference BetweenQuarks and
Gluons at High pT
Baryons more likely from gluon fragmentations in
the pQCD region
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No Significant Difference Between Heavy
Quark Meson and Light Quark Mesons
Non-photonic electrons from heavy quark decays
Charged hadrons
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High pT Phenomena at RHIC
Very dense matter has been created in
central AuAu collisions! This dense matter is
responsible for the disappearance of
back-to-back correlation and the suppression of
high pT particles ! The mechanism for parton
energy loss is yet to be understood ! The
dynamics of jet-medium interactions (Mach cone
or not) requires more studies !
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Elliptic Flow Parameter v2
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Elliptic Flow ultra-cold Fermi-Gas

• Li-atoms released from an optical trap exhibit
  elliptic flow analogous to what is observed in
  ultra-relativistic heavy-ion collisions
• Elliptic flow is a general feature of strongly
  interacting systems!

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Elliptic Flow v2
PRL 92 (2004) 052302 PRL 91 (2003) 182301
Hydro calculations break-down at higher pT (as
expected). How is v2 established at pT above 2
GeV/c? Why is baryon v2 larger than meson v2?
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Constituent Quark Degree of Freedom
Hadronization Scheme for Bulk Partonic
Matter

• KS two quark coalescence
• three quark coalescence
• from the partonic matter surface?!
• Particle v2 may be related to
• quark matter anisotropy !!

pT lt 1 GeV/c may be affected by hydrodynamic
flow !
Quark Coalescence (ALCOR-J.Zimanyi et al,
AMPT-Lin et al, RafelskiDanos,
MolnarVoloshin ..) Quark Recombination (R.J.
Fries et al, R. Hwa et al)
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Constituent Quark Scaling
Constituent (n) Quark Scaling -- Meson n2 and
Baryon n3 grouping Some deviation due to
internal hadron structure
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Strangeness from Bulk Partonic Matter
RCP
X
L
Constituent Quark Number Scaling -- Hadronization
through quark clustering -- Effective DOF
constituent quarks quasi-hadrons
at Tc ? Lattice QCD picture?
W
f
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Intermediate pT Dynamics
At hadronization the manifested effective degrees
of freedom seem to be in constituent quarks !
Multi-parton dynamics clustering of quarks
could be responsible for -- increased
baryon production -- strange baryon
enhancement -- strong elliptic flow
at intermediate pT !!!
Hadronization of bulk partonic matter --
different phenomenon from ee- collisions !
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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 ! The fact
that in order to explain the v2 of hadrons
individual constituent quarks (n2-meson,3-baryon)
must have a collective elliptic flow v2 and
the hadron v2 is the sum of quark v2 ? Strong
Evidence for Deconfiement !
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Discoveries from Unexpected Areas?!
RHIC -- Frontier for bulk partonic matter
formation (quark clustering and
rapid hadronization) -- Factory for
exotic particles/phenomena
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RHIC Exotic Particle Factory
STAR Exciting Physics Program A full TOF
upgrade will greatly enhance STARs capability !!
Chinese STAR Group SINAP Tsinghua University
USTC CCNU, Wuhan IMP, Lan Zhou IHEP
Construction to be finished by 2008 Full
installation in 2009
Full Barrel TOF Using MRPC
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RHIC Physics Outlook
Heavy Ion Physics 1) Properties of high
density QCD matter 2) Chiral symmetry at high
temperature and density 3) Search for exotic
particles/phenomena at RHIC 4) Search for
critical point (low energy scan) RHIC Spin
Physics Using Polarized pp Collisions 1) the
gluon spin structure function ? major
milestone to understand the spin of the proton!
2) sea quark spin structure function 3) quark
transverse spin distribution
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End of Talk
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Heavy quark energy loss Early Expectations
Radiative energy loss of heavy quarks and light
quarks --- Probe the medium property !
What went wrong?
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B and D contributions to electrons
Experimental measurement of B and D
contributions to non-photonic electrons
! Direct measurement of D and B mesons
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Au Au Collisions at RHIC
Central Event
(real-time Level 3)
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pT Scales and Physical Processes
RCP
Three PT Regions
-- Fragmentation
-- multi-parton dynamics (recombination or
coalescence or )
-- Hydrodynamics (constituent quarks ?
parton dynamics from gluons to
constituent quarks? )
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The Field Feynman picture of cascade
fragmentation
Kretzer_at_ISMD04
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Baryon Production from pQCD
ee-?jet fragmentation from SLD
p
p
K
K
p
p
Normal Fragmentation Cannot Produce the Large
Baryon Yield
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Too Many Baryons at Intermediate pT
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STAR preliminary data motivated sonic-boom
prediction
Actually sonic-boom was first predicted in the
70s by the Frankfurt school.
Many recent studies H. Stoecker,
nucl-th/0406018. Muller, Ruppert,
nucl-th/0507043. Chaudhuri, Heinz,
nucl-th/0503028. Y.G. Ma, et al. nucl-th/0601012.
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Experimental Statistical and Systematic Errors
c-cbar production CS PHENIX 0.92-0.15-0.54
mb 0.567-0.057-0.224 mb STAR 1.4-0.2-0.4
mb Errors taken seriously High pT region does
not contribute to total CS much. Difference
between STAR and PHENIX has to be resolved !!
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Intriguing Situation Regarding Pentaquark States
D
M (GeV/c2)
M (GeV/c2)
Statistical significance 4s Intriguing ! Not
conclusive yet ! Another long dAu run will
resolve this uncertainty !
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Radiative Energy Loss not Enough
Moore Teaney, PRC 71, 064904 (2005)
Large collisional (not radiative) interactions
also produce large suppression and v2
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Charm Quark in Dynamical Model (AMPT)
Large scattering cross sections needed !
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Spin Physics Program
The Spin Structure of the Proton ½ ½ SDq
DG ltLgt q ? up, down and strange quarks G ?
gluons L ? angular momentum of quarks and gluons
Experimentally 1) total spin in quarks 30
2) sea quarks are polarized too 3) little info
about the gluon polarization 4) even less know
about ltLgt and how to measure ltLgt