Quark-Gluon Plasma

1
Quark-Gluon Plasma

• Sijbo-Jan Holtman

2
Overview

• Introduction
• Phases of nuclear matter
• Thermodynamics
• Experiments
• Conclusion

3
Introduction

• Research of quark-gluon plasma important to
  understand early universe and center of neutron
  stars

4
The Phases of Nuclear matter

• Normal nuclei density ?0 , temperature T0
• Gas peripheral collision between gold nuclei

5
Phases of Nuclear matter
Hadronic matter

• Central collision
• N N ? N , new degree of freedom
• dynamical equilibrium between pN and ?
• Boltzmann distribution
  dN / dE cst e -E / kT (E is kinetic
  energy)
• kTlt 150 MeV

6
Phases of nuclear matter

• Central collision between gold nuclei

7
Phases of nuclear matter

• Quark-gluon plasma (QGP) or Quark soup

Hadron gas

• ?0 (6 fm3) -1 volume of
  nucleon is 10 / ?0
• For T gt 200 MeV enough energy for nucleon-nucleon
  interaction to increase collision frequency very
  much
• The disintegration of nucleons and pions into
  quarks and gluons

QGP
8
Phases of nuclear matter

• Phase diagram

Big Bang
Normal nuclear matter
Neutron stars
9
Thermodynamics

• Derivation of the equation of state

• Gluons, u and d quarks massless
• all interactions neglected
• degrees of freedom Gluons Ng
  2(spin) 8(colour) 16
  Quarks Nq 2(spin) 3(colour) 2(flavour)
  12
• energy density in each degree of freedom

10
Thermodynamics
Gluons
eg (dp)p(eßp-1) -1 p2T4 / 30
Quarks and anti-quarks

• eq (dp) p (e(ßp-µ)1) -1 x (ßp-µ)
  T4 /2p2 dx (xßµ)3 (e x1) -1
• eq (dp) p (e(ßpµ)1) -1 x (ßpµ)
  T4 /2p2 dx (x-ßµ)3 (e x1) -1
• eq eq 7p4 T4/120 µ2 T4/4 µ4/8 p2

11
Thermodynamics

• The total energy density for µ0 (same amount
  of quarks as anti-quarks)
• e 16 eg 12 (eq eq) (T/160 MeV)4
  GeV/fm3
• Compare with
• enuc 125 MeV/fm3 e of nuclear matter
• eN300-500 MeV/fm3 e inside nucleon

12
Thermodynamics

• Determining a physically realistic µ with the
  baryonic density
• nb 1/3 12 (nq nq) nq (dp)
  (e(ßp-µ)1) -1
• nb 2 µT2/3 2µ3/3p2
• Consequences

• High temperature µ T-2/3
• nb 4/3 de/dµ (also valid with interactions)

13
Thermodynamics

• In the same way
• P1/3 e s 1/3 de/dT
• Range of stability of QGP
• P can balance B the external vacuum pressure
• B p2Tc4(37/90-11as/9p)(1-2as/p)(xc21/2 xc4)
• µ cxcpTc
• e (T/160 MeV)4 GeV/fm3
• ec ½-2 GeV/fm3

14
Thermodynamics

• Phase diagram according to the calculation
• Only 10-15 percent difference between
  interaction included and interaction excluded

15
Experiments

• J/? suppression because colour screening hinders
  the quarks from binding
• Strangeness and charm enhancement

16
Experiments

• Jet quenching

• Hard scatterings (HS) produce jets of particles
• In a colour deconfined medium the partons
  strongly interact and loose energy by gluon
  radiation
• HS near the surface can give a jet in one
  direction, while the other side is quenched

17
Experiments

• Search for QGP done at Relativistic Heavy Ion
  Collider (RHIC) on Long Island, New York

18
Experiments

• PHENIX Pionering High Energy Nuclear Interaction
  eXperiment

• AuAu till 100 GeV, dAu and pp till 250 GeV

19
Experiments

• Aud similar to peripheral AuAu

20
Experiments

• Aud similar to peripheral AuAu
• Away side strongly suppressed in AuAu

21
Experiments

• Central collision simulation

22
Conclusion

• QGP not yet experimentally verified
• Problems remain T0, high ? (neutron stars)
  and high T, low ? experimentally difficult to
  realize