Lattice QCD Calculations

1
Lattice QCD Calculations
Chiral Condensate
The vacuum melts at TTC !
Boyd G, et al., Phys. Lett. 349B170 (1995)
Energy Density and Pressure
Blum T, et. al., Phys. Rev. D 515153 (1995)
The energy density and pressure rise with the
release of color degrees of freedom and chiral
symmetry restoration!
2
Quantum Chromodynamics (QCD)

• Fundamental theory of the interaction between
  quarks and gluons
• The strength of the QCD interaction grows at
  large distances -
• quarks confined into color singlet states
  (hadrons).

Strong Potential
V
r
Strong Coupling Constant
?EFF (Q 2)
?QED (Q 2)
?QCD (Q 2)
confinement
assymptotic freedom
Q 2
r
3
Heavy-Ion Collisions

• Provides the ability to study the
  non-perturbative regime of
• QCD in the laboratory - high baryon density
  and/or high T
• Not just a superposition of NN collisions - the
  matter created
• (either the QGP or superheated hadron gas) may
  be described
• as a thermodynamic state in thermal (and
  chemical?)
• equilibrium
• Makes possible the study of exotic states of
  matter (strangelets, etc.)

PHASE DIAGRAM OF NUCLEAR MATTER
TC 150 MeV
DECONFINED QUARKS AND GLUONS
(QGP)
RHIC or LHC
HADRONIC MATTER
Temperature
AGS
DECONFINEMENT
Early Universe
Supernovae and Neutron Stars
Ordinary Nuclei
?nm
5-10 ?nm
Baryon Density
4
Non-Strange and Strange Antibaryons in AuPb
Collisions at 11.5 A GeV/c
John Lajoie Yale University
1. Quantum Chromodynamics and the
Deconfinement Phase Transition A. Structure
of the QCD vacuum B. Lattice QCD
predictions 2. Heavy Ion Collisions A.
Phase diagram of nuclear matter B. Probes
of heavy ion collisions 3. Experiment E864 at
the BNL-AGS A. Antiproton production B.
Implications for antihyperon production C.
Antideuterons D. Future prospects for
E864 4. Conclusions
Iowa State University - 3 March 1997
5
Probes of Heavy Ion Collisions
Coalescence explores phase space density at
freezeout
HBT Interferometry source size and lifetime
Freezeout
Hadronization
Antimatter both early (production) and late
(annihilation) stages of collision
Leptons and Photons early stages of
collision, meson mass shifts
x
QGP or Superheated Hadron Gas?
Exotic Particles strangelets probe QGP formation
t
Different probes study different stages in the
time history of the colliding nuclei
6
Physics Goals of E864
SEARCH FOR
1. Strangelets at ??few x 10-10 per
collision, with coalescence limits reached for
AS ? 12 for Z ? 0, sensitivity of 10-6 to
10-8 for neutrals 2. H0 and composites (H0 H0,
H0d) for tH gt 50ns 3. Surprises!
MEASURE
1. Antimatter (p, d) 2. Light nuclei produced in
central collisions (d, t, 3He,..., A ? 12 at
the limit of sensitivity)
Both will cover a large range of rapidity (?y
?0.5) and transverse momentum (Pt /Z ? 2Gev/c)
7
neagtive kaon measurements in good agreement
with E877, E878
preliminary He3 measurements compare well
between E864 and E878
8
A statistical analysis of E864 and E878 data,
including statistical and systematic errors,
concludes
E859 SiAu Collisions
B.A. Cole, Nucl. Phys. A590 (1995) Yeudong
Wu, HIPAGS 96
Minv for p?? and p?? pairs, before and after
background subtraction.
9
Average antiproton multiplicity as a function of
available energy in C.M. (J. Costales, Ph.D.
Thesis, M.I.T. 1990)
10
Ratio of E864 to E878 at Midrapidity and pT0
E864 open geometry same acceptance for
pbars from antihyperon decay as for
primordial antiprotons
E878 focussing spectrometer small acceptance
for antiprotons from antihyperon decay at
midrapidity (14 for antilambda, 10 for
antisigma) Yale Preprint 40609-1148, to be
submitted to Phys. Rev. C.
The two experiments make different measurements!
11
RQMD v1.07
full annihilation
no annihilation
Antiprotons are annihilated in the center of the
fireball, and at freezout are distributed in a
shell around the high baryon-density center.
12
Future Prospects

• 1996 Data Run with LET enhancement of minbias
  sample

Energy
Time
Recorded 45 million interactions with LET
enhancement of pbar sample by a factor if 27 -
equivalent to 1.2 billion interactions.
Over 40,000 pbars in sample - study production as
a function of collision centrality.
ALSO
A study of pbar production with respect to the
reaction plane of the two colliding nuclei may
be possible.
An attempt to measure antineutron production is
underway.
13
Antideuterons
J. Nagle, S. Kumar, H. Sorge
Preliminary E864 Limit
The antideuteron is sensitive to the pbar phase
space density at freezeout.
14
Antiproton Annihilation
P. Koch and C. Dover, PRC 40 (1989) 145
A large annihilation cross section is a long
range effect -
15

• pp Collisions

• Cascade Models

• Thermal Models

• Associated production reactions

• Pauli blocking of u,d states

• Different annihilation cross section for
  antilambda and
• antiproton (quark content)?

16
Conclusions
E864 antiproton measurements indicate that most
antiprotons detected are the decay products of
antihyperons. This indicates an enhancement of
strange antibaryons in AuPb collisions at the
AGS.
This enhancement is inconsistent with thermal and
transport models of heavy ion collisions at AGS
energies.
What can we look forward to at RHIC?

• lower baryon density in the central region,
• but a much higher energy density
• higher particle multiplicity - several dozen
  antiprotons
• per central AuAu event at 100 A GeV/c!!