Transcript Document

Bulk Properties of QCD – matter at
Highest Colider Energies
Kai Schweda, University of Heidelberg / GSI Darmstadt
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ISMD, Berkeley, Aug 4 - 9, 2007
Kai Schweda
QCD Phase Diagram
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Outline
Identify and study QCD bulk-matter with
partonic degrees of freedom:
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Gobal observable - multiplicity
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Chemical freeze-out, Tch and mB
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Partonic collectivity, Tfo and bT
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Heavy – quark collectivity
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Summary
ISMD, Berkeley, Aug 4 - 9, 2007
Kai Schweda
Mid - rapidity Densities
PHOBOS fit
HIJING BBar
Armesto et al.
AMPT
Eskola
CGC
KLN
ASW
DPMJET-III
EHNRR
 at LHC, dN/dh  1000 - 3000
 estimate energy density  Bj 
PHOBOS compilation: W. Busza, SQM07.
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1 1 dET
 R 2  0 dy
Theory points: HI at LHC – last call for predictions, CERN, May 2007.
ISMD, Berkeley, Aug 4 - 9, 2007
Kai Schweda
EoS from Lattice QCD
1) Large increase in  !
SPS
RHIC
LHC ?
 Large increase in Ndof:
Hadrons vs. partons
2) TC ~ 160 MeV
3) Boxes indicate max. initial
temperatures
 Longest expansion
duration at LHC
 Expect large partonic
collectivity at LHC
Z. Fodor et al, JHEP 0203:014(02)
C.R. Allton et al, hep-lat/0204010
F. Karsch, Nucl. Phys. A698, 199c(02).
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Chemical Freeze - out
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Hadron Yield - Ratios
1) At RHIC:
Tch = 160 ± 10 MeV
mB = 25 ± 5 MeV
2) S = 1.
 The hadronic
system is
thermalized at RHIC.
3) Short-lived resonances
show deviations.
 There is life after
chemical freeze-out.
RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184;
Statistical Model calculations: P. Braun-Munzinger et al. nucl-th/0304013.
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Kai Schweda
Chemical Freeze-Out vs Energy
With increasing energy:
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Tch increases and saturates
at Tch = 160 MeV
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Coincides with Hagedorn
temperature
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Coincides with early lattice results
 limiting temperature for
hadrons, Tch  160 MeV !

mB decreases, mB = 1MeV at LHC
 Nearly net-baryon free !
A. Andronic et al., NPA 772 (2006) 167.
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Baryon Ratios
With increasing energy:
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Baryon ratios approach unity
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At LHC, pbar / p  0.95
 challenge,
need 1% precision to
address net-baryon
transport !
Compilation: N. Xu
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Partonic Collectivity
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Elliptic Flow
“Elliptic flow is larger for
pions but smaller for
protons at LHC than at
RHIC”.
This is expected
from simple, hydrolike blast-wave fits !
 larger collective
flow: mass ordering
more pronounced !
Theory points: C.M. Ko – last call for predictions, CERN, May 2007.
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Collectivity - Energy Dependence

Collectivity parameters <bT>
and <v2> increase with energy

Two extreme secenarios:
(a) Tfo  Tch AND bT  0.8
 pure partonic
collectivity at LHC!
(b) Tfo  Tch , bT  0.3
 no collectivity,
no QGP !
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Quark Masses
1)
2)
Higgs mass: electro-weak
symmetry breaking. (current
quark mass)
QCD mass: Chiral symmetry
breaking. (constituent quark
mass)
 Strong interactions do not
affect heavy-quark
masses.
 Important tool for studying
properties of the hot/dense
medium at RHIC and LHC.
Total quark mass (MeV)
 Test pQCD predictions at
RHIC and LHC.
X. Zhu, M. Bleicher, K.S., H. Stoecker, N. Xu et al., PLB 647 (2007) 366.
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Charm Correlations
c-cbar are correlated
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Pair creation: back to back
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Gluon splitting: forward
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Flavor excitation: flat
Correlations vanish
 frequent interactions
among partons !
 probe light-quark
thermalization !
Pythia calcs.: G. Tsiledakis.
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Hadronic Re-scattering
 Hadronic re-scattering can not completely wash out DD-correlations
 Frequent partonic re-scattering needed  light quark thermalization !
X. Zhu, M. Bleicher, K.S., H. Stoecker, N. Xu et al., PLB 647 (2007) 366.
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J/y Production
P. Braun-Munzinger and J. Stachel, Nature 448 (2007) 302.
 suppression,
compared to
scaled p+p
(SPS)
 regeneration,
enhancement
Low energy (SPS):
few ccbar quarks in the system  suppression of J/y
High energy (LHC):
many ccbar pairs in the system  enhancement of J/y
 Signal of de-confinement + thermalization of light quarks !
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Predictions for LHC
 large ccbar production at
LHC
scc
 corona effects negligible
 regeneration of J/y
dominates
 striking centrality
dependence
Signature for QGP
formation !
 Initial conditions at LHC ?
A. Andonic et al., nucl-th/0701079.
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Multiply Heavy-flavored Hadrons
 Statistical hadronization
- de-confined heavy-quarks
- equilibrated heavy-quarks
 Enhancement up to x1000 !
Quarks and gluons  hadrons
Pb+Pb
 Need total charm yields
c
Wccc / D :
c
 Measure Xcc, Wcc, Bc, (Wccc)
x1000
 Probe deconfinement and
thermalization @ LHC
c
p+p
 QGP !
F. Becattini, Phys. Rev. Lett. 95, 022301 (2005);
P. Braun-Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013.
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Heavy - Quark Production
1)
Charm x 10
2)
Beauty x 100
3) Heavy-quarks abundantly produced at LHC !
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STAR data: A. Suaide, P. Djawothoto QM2006;
Calcs.: R. Vogt.
Kai Schweda
Mid - Rapidity Performance
ATLAS
CMS
Low – momentum
 ALICE: large momentum coverage in full azimuth
 CMS/ATLAS: Si only tracking
 address bulk properties !
 CMS: pT > 0.150 GeV
 characterize Quark
Gluon Plasma !
CMS: TDR.v2, CERN-LHCC-2007-009; ATLAS: B. Cole, SQM2007; ALICE: PPR.vol.II, J. Phys. G 32 (2006) 1295.
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J/y  e+ + e- Reconstruction
J/y: c
c
: b
b
 J/y  e+ + e identify electrons
through their transition
radiation
 Precise
Measurement of
Quarkonia !
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D - Meson Performance
 Measure secondary vertex
 Direct reconstruction of D0
 precise measurement
of total heavy-quark yield
 address heavy – quark
collectivity !
ALICE: PPR.vol.II, J. Phys. G 32 (2006) 1295.
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Summary
 Bulk properties at LHC:
dN / dh  1000 – 3000
Tch  160 ± 10 MeV, mB  0 – 5 MeV
Tfo  Tch  all collectivity from partonic stage
<bT> = 0.8 ± 0.05 (c), <v2>  0.08
 Measure spectra, correlations and v2 of:
D0, D+, Ds, J/y, Lb,
to identify and characterize QGP !
 ALICE is well suited for these studies
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