Quark-Gluon Plasma Sijbo-Jan Holtman

Overview Introduction Phases of nuclear matter Thermodynamics Experiments Conclusion

Introduction Research of quark-gluon plasma important to understand early universe and center of neutron stars phase transition!

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

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

Phases of nuclear matter Central collision between gold nuclei

Phases of nuclear matter Quark-gluon plasma (QGP) or Quark soup Hadron gas ρ0 = (6 fm3) -1 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

Phases of nuclear matter Phase diagram Big Bang Normal nuclear matter Neutron stars

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

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

Thermodynamics The total energy density for μ=0 (same amount of quarks as anti-quarks) ε = 16 εg + 12 (εq + εq) = (T/160 MeV)4 GeV/fm3 Compare with εnuc = 125 MeV/fm3 ε of nuclear matter εN=300-500 MeV/fm3 ε inside nucleon

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)

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

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

Experiments J/Ψ suppression because colour screening hinders the quarks from binding Strangeness and charm enhancement

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

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

Experiments PHENIX: Pionering High Energy Nuclear Interaction eXperiment Au+Au till 100 GeV, d+Au and p+p till 250 GeV

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

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

Central collision simulation Experiments Central collision simulation

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