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
phase transition!

4. The Phases of Nuclear matter
Normal nuclei : density ρ0 , temperature T=0
Gas: peripheral collision between gold nuclei

5. Phases of Nuclear matter
Hadronic matter
Central collision
N + N = Δ + N , new degree of freedom
dynamical equilibrium between πN and Δ
Boltzmann distribution dN / dE = cst e -E / kT (E is kinetic energy)
kT< 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
ρ0 = (6 fm3) volume of nucleon is 10 / ρ0
For T > 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) = Quarks: Nq = 2(spin) × 3(colour) × 2(flavour) = 12
energy density in each degree of freedom

10. Thermodynamics Gluons εg = (dp)p(eβp-1) -1= π2T4 / 30
Quarks and anti-quarks
εq = (dp) p (e(βp-μ)+1) x= (βp-μ) = T4 /2π dx (x+βμ)3 (e x+1) -1
εq = (dp) p (e(βp+μ)+1) x= (βp+μ) = T4 /2π dx (x-βμ)3 (e x+1) -1
εq + εq = 7π4 T4/120 + μ2 T4/4 + μ4/8 π2

11. Thermodynamics
The total energy density for μ=0 (same amount of quarks as anti-quarks)
ε = 16 εg (εq + εq) = (T/160 MeV)4 GeV/fm3
Compare with
εnuc = 125 MeV/fm3 ε of nuclear matter
εN= MeV/fm3 ε inside nucleon

12. Thermodynamics
Determining a physically realistic μ with the baryonic density
nb = 1/3 12 (nq – nq); nq = (dp) (e(βp-μ)+1) -1
nb = 2 μT2/3 + 2μ3/3π2
Consequences:
High temperature μ ~ T-2/3
nb = 4/3 dε/dμ (also valid with interactions)

13. Thermodynamics In the same way P=1/3 ε; s = 1/3 dε/dT
Range of stability of QGP:
P can balance B the external vacuum pressure
B = π2Tc4[(37/90-11αs/9π)+(1-2αs/π)(xc2+1/2 xc4)]
μ c=xcπTc
ε = (T/160 MeV)4 GeV/fm3
εc = ½-2 GeV/fm3

14. Thermodynamics Phase diagram according to the calculation
Only percent difference between interaction included and interaction excluded

15. Experiments
J/Ψ 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
Au+Au till 100 GeV, d+Au and p+p till 250 GeV

19. Experiments Au+d similar to peripheral Au+Au Escaping Jet “Near Side”
Lost Jet
“Away Side”
Au+d similar to peripheral Au+Au
d+Au
Au+Au
Near
Away

20. Experiments Au+d similar to peripheral Au+Au
Escaping Jet
“Near Side”
Lost Jet
“Away Side”
Au+d similar to peripheral Au+Au
Away side strongly suppressed in Au+Au
Near
Away
d+Au
Au+Au

21. Central collision simulation
Experiments
Central collision simulation

22. Conclusion QGP not yet experimentally verified
Problems remain: T=0, high ρ (neutron stars) and high T, low ρ experimentally difficult to realize