Phase Diagram of Nuclear Matter

1
Phase Diagram of Nuclear Matter
hadrons quarks and gluons hadrons
2
STAR Experiment at the RHIC Collider
3
Particle Tracks in the Time Projection Camber
Head-on AuAu collision in STAR TPC
1500 charged hadrons and leptons
4
Can we prove that we have a phase thatbehaves
different than elementary pp collisions ?
Proving the existence of a new phase of matter

• Three steps
• a.) prove that the phase is partonic
• b.) prove that the phase is collective
• c.) prove that the phase characteristics are
  different from the QCD vacuum

5
Particle Production and Observables
Medium (low pT) Probing Medium (high pT) AuAu
vs pp (medium vs no medium)
Hydro elliptic flow v2
v2
Partonic stage (early)
Thermal spectra
Spectra AuAu/pp
Particle yields
Hadronic stage (late)
jet correlations
6
Elliptic flow (anisotropic) Flow a strong
indicator of collectivity
Reaction plane
f

• non-central collisions azimuthal anisotropy in
• coordinate-space.
• interactions ? asymmetry in momentum-space.
• sensitive to early time in the systems
  evolution.
• Measurement
• Fourier expansion of the azimuthal pT
  distribution.

7
Probing the Medium with high Momentum Particles
(Jets)
p
pp collisions ?? no medium
p
what happens in AuAu to jets which pass
through medium?
?

• scattered quarks radiate energy
• ( GeV/fm) in the colored medium
• quenches high pT particles
• kills jet partner on other side

AuAu
8
High-pT suppression (jet quenching)
STAR, nucl-ex/0305015
pQCD Shadowing Cronin
energy loss
pQCD Shadowing Cronin Energy Loss

• Deduced initial gluon density at t0 0.2 fm/c
  dNglue/dy 800-1200
• 15 GeV/fm3, eloss 15cold nuclear matter
  (compared to HERMES eA) ?
  radial partonic energy loss at RHIC (not
  collisional)
  (e.g. X.N. Wang
  nucl-th/0307036)

9
Di-Jet Quenching in extended Medium
away
near
Trigger particle pT 4-6 GeV Correlated particle
pT 2-4 GeV
STAR Preliminary
(no medium)

• Away-side suppression
• Suppression larger in out-of-plane
• Path length dependence of energy loss

10
Resonances are the Key Probe for QCD Phase
Transition(s)
Because of lifetime and strong interactions with
the medium, light vector mesons are the only
probe of chiral symmetry restoration
Because of color screening in the medium, heavy
vector mesons are the most sensitive probe of
deconfinement conditions
11
Sensitivity to Deconfinement Conditions
Matsui Satz (1986) (Phys. Lett. B178 (1986)
416) Color screening of heavy quarks in QGP leads
to heavy resonance dissociation.
Melting at SPS
Thermometer for early stages Tdis(Y(2S)) lt
Tdis(?(3S))lt Tdis(J/Y) ? Tdis(?(2S)) lt Tdis(?(1S))
Lattice QCD predictions
Lattice QCD SPS TInitial 1.5 Tc RHIC
TInitial 2 Tc
The suppression of heavy quark states signature
of deconfinement at QGP.
J/Y (cc-bar) ? e e-, m m- ? (bb-bar)
? e e-, m m-
12
Chiral Symmetry Restoration
Leptonic and hadronic decay f(1020) ? e e- ,
mm- BR 0.0003 f(1020) ? K K-
BR 0.50 Mass (e e-)
0.001 GeV Mass (K K- ) 0.987 GeV Effective
mass drops ? hadronic decay closes up. ?
Increase of BR ratio
We expect a initial density in a heavy ion
reaction of 5-20 times of r0
T. Hatsuda and S. Lee Phys. Rev. C46 (1992) 34