JJalilian Marian PPTMac

Color Glass Condensate at RHIC: 

Color Glass Condensate at RHIC Jamal Jalilian-Marian Institute for Nuclear Theory Seattle, Washington

OUTLINE: 

OUTLINE Quantum Chromo Dynamics Perturbative QCD Parton Model Semi-Classical QCD Color Glass Condensate Color Quantum Fluid Semi-Classical QCD at RHIC Indications Tests

Perturbative QCD: 

Perturbative QCD Quarks, gluons (x, Q2) Weak coupling (s << 1) Collinear factorization Incoherence Dilute systems

Semi-Classical QCD: 

Semi-Classical QCD Wilson lines Weak coupling (s << 1) Classical fields + renormalization group Coherence (longitudinal): lc ~ 1/mN x Dense systems

Gluon Saturation: 

Small X/Large A Large occupation number Coherent state Saturation momentum Qs (x) Gluon Saturation

Slide6: 

Color Glass Condensate Pt < Qs(y) Color Quantum Fluid Qs(y) < Pt < Qes(y) Dilute Parton Gas Pt > Qes(y) Where is RHIC? Qs Qes

QCD: Kinematic Regions: 

QCD: Kinematic Regions Color Glass Condensate High gluon density Strong classical fields Non-Linear evolution: JIMWLK (BK at large Nc) Color Quantum Fluid Low gluon density Linear evolution: BFKL Anomalous dimension (kt factorization) Dilute Parton Gas Low gluon density Linear evolution: DGLAP No anomalous dimension (collinear factorization)

Coherence at RHIC: 

Coherence at RHIC Multiplicity growth: from pp to AA Incoherent scattering ~3 Coherent scattering ~ 50%

Color Glass Condensate at RHIC: 

Color Glass Condensate at RHIC Gluon production Multiplicities are correctly predicted Beware of the fragmentation region

Color Glass Condensate at RHIC: 

Color Glass Condensate at RHIC Energy, Npart dependence: OK Warning: saturation at s ~ 20 GeV !

Color Quantum Fluid at RHIC?: 

Color Quantum Fluid at RHIC? RAA < 1: initial state? BFKL anomalous dimension: 1/Q2 ---> (1/Q2)0.6 Approximate Npart scaling 2 ---> 1 processes (reduced back to back correlations)

dA:Mid Rapidity: 

dA:Mid Rapidity R_dA (pt > 2 GeV) Quantum evolution: not the dominant physics Classical: MV model (Cronin effect)? Correlations (pt > 4 GeV) CGC: not the dominant physics

RHIC: Color Glass Condensate?: 

RHIC: Color Glass Condensate? HERA (protons): X ≤ 0.01 Mid rapidity RHIC (AA): Pt ~ 5 GeV --> X ~ 0.1 Pt ~ 1 GeV --> X ~ 0.01 Multiplicity (P_t < 1 GeV): OK High Pt spectra: X is too large Color Glass Condensate provides the initial conditions, but the physics of high pt is that of final state rescattering, energy loss, …. Look forward in dA

dA: The Common Approach: 

dA: The Common Approach Two main effects Cronin Intrinsic momentum F(x, Q2) --> F(x, kt2, Q2) <kt2>pA = <kt2>pp + k H[n] Parameters from fitting data at low energy Shadowing Parameterize the data on structure functions Gluon shadowing? Phenomenological models Parameters are process, energy, etc. dependent No Universality ---> Predictability ?

dA: The CGC Approach: 

dA: The CGC Approach

Going Forward at RHIC: 

Going Forward at RHIC Assume saturation works for x ≤ x0 [x0~10-2 --> Qs(x0) ~ 1.6 GeV] For x ~ x0: classical approximation (MV model) Suppression (enhancement) at pt < (>) Qs Forward: y = 0 ---> 2 ---> 4 x ~ 10-2 ---> 10-3 ---> 10-4 << x0 (pt ~ 2 GeV) Quantum evolution becomes essential Qs(y0) = 1.6 GeV ---> Qs(y=4) = 2.6 GeV Qes(y0) = 1.6 GeV ---> Qes(y=4) = 4.2 GeV Suppression at pt < Qes Centrality Reduced correlations (2 ---> 1 processes are dominant) Forward rapidity: CGC and CQF regions open up

Forward Rapidity dA: 

Forward Rapidity dA Illustration Suppression of RdA as we go forward

Forward Rapidity dA: 

Forward Rapidity dA

Forward Rapidity dA at RHIC: 

Forward Rapidity dA at RHIC Deuteron fragmentation region Deuteron: large x1 Nucleus: small x2 The experimental coverage STAR: neutral pions at y = 0, 4 BRAHMS: charged hadrons at y = 0, 1, 2, 3 PHENIX: dileptons at y = 0, 2 Map out the QCD kinematic regions at RHIC (pt, y, correlations, centrality) Hadrons (Zave < 1 ---> higher pt partons) Photons, dileptons, photon + jet

Dilepton Production in dA: 

Dilepton Production in dA No final state interactions Dipole cross section Additional handle: M2 PHENIX: l+l- at y = 1.2 - 2.4

Dilepton Production in dA: 

Dilepton Production in dA y = 2.2 Integrated over pt RdA < 1

Summary: 

Summary CGC is a new and exciting aspect of QCD CGC provides the initial conditions for formation of QGP in heavy ion collisions There are strong hints of CGC/CQF at RHIC Multiplicity, energy dependence, forward rapidity spectra, … Further tests: electromagnetic signatures, back to back correlations, centrality … Forward rapidity region in dA is the best place to explore CGC/CQF at RHIC