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Quark Matter at High Density/Temperature. James C Dunlop Brookhaven National Laboratory. Defining the question. Recent Definition from STAR for the Quark Gluon Plasma.

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Quark matter at high density temperature

Quark Matter at High Density/Temperature

James C Dunlop

Brookhaven National Laboratory

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Defining the question
Defining the question

Recent Definition from STAR for the Quark Gluon Plasma

QGP  a (locally) thermally equilibrated state of matter in which quarks and gluons are deconfined from hadrons, so that color degrees of freedom become manifest over nuclear, rather than merely nucleonic, volumes.

Contrast with other recent definition:

Approximately thermalized matter at energy densities so large that the simple degrees of freedom are quarks and gluons. This energy density is that predicted by LGT for the existence of a QGP,  2 GeV/fm3.

M. Gyulassy & L. McLerran

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Rhic implementation
RHIC Implementation

PHOBOS

BRAHMS &PP2PP

RHIC

PHENIX

1.2 km

STAR

  • Flexibility is key to understanding complicated systems

    • Polarized protons, sqrt(s) = 50-500 GeV

    • Nuclei from d to Au, sqrt(sNN) = 20-200 GeV

  • Physics runs to date

    • Au+Au @20,62,130,200 GeV

    • Polarized p+p @200 GeV

    • d+Au @ 200 GeV

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Rhic experiments
RHIC Experiments

Four experiments, two large, two small:

STAR: Large acceptance (Df = 2p, Dh = 2-6)

PHENIX: Electron/muon identification, high rate trigger, limited acceptance (Df = p, Dh = 0.5 (central arm)

PHOBOS: Tabletop: limited tracking acceptance, largest multiplicity acceptance of all experiments

BRAHMS: Forward tracking in classical spectrometer

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Lattice qcd predicts a rapid transition
Lattice QCD Predicts a RAPID Transition

in entropy density, hence pressure

in heavy-quark screening mass

The most realistic calcs.  no discontinuities in thermodynamic proper-ties @ RHIC conditions (i.e., no 1st- or 2nd-order phase transition), but still crossover transition with rapid evolution vs. temperature near Tc 160 – 170 MeV.

in chiral condensate

Quark Matter at High Density/Temperature James Dunlop ICHEP04


But only smooth behavior is observed
But only smooth behavior is observed

HBT parameters

Charged particle pseudo-rapidity density

pT-integrated elliptic flow

pT-integrated elliptic flow, scaled by initial spatial eccentricity

No exp’tal smoking gun!  Rely on theory-exp’t comparison

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Chemical equilibration hadron yield ratios
Chemical Equilibration? Hadron Yield Ratios

STAR

O PHENIX

Strangeness Enhancement

Resonances

  • pT-integrated yield ratios in central Au+Au collisions consistent with Grand Canonical stat. distribution @ Tch = (160 ± 10) MeV, B  25 MeV, across u, d and s sectors (s consistent with 1.0).

  • Inferred Tch consistent with Tcrit (LQCD)  T0 =~ Tcrit .

  • Does result point to thermodynamic and chemical equilibration, and not just phase-space dominance? Also works in e+e-, p+p

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Collective behavior azimuthal anisotropy v 2
Collective Behavior: Azimuthal Anisotropy v2

coordinate-space-anisotropy  momentum-space-anisotropy

y

py

px

x

Pressure converts initial coordinate-space

Anisotropy into final momentum-space anisotropy

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Time evolution in ideal hydrodynamics
Time evolution in Ideal Hydrodynamics

  • Elliptic Flow reduces spatial anisotropy -> shuts itself off

  • Sensitive to EARLY TIMES

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Analogy to ultracold atoms
Analogy to Ultracold Atoms

Extremely cold system at T=10 nK or 10^(-12) eV can produce micro-bang

Elliptic flow with ultracold trapped Li6 atoms, a=> infinity regime

The system is extremely dilute, but can be put into a hydro regime, with an elliptic flow, if it is specially tuned into a strong coupling regime via the so called Feshbach resonance

Analogy pointed out by Shuryak

Quark Matter at High Density/Temperature James Dunlop ICHEP04


V 2 vs ideal hydrodynamics
v2 vs. Ideal Hydrodynamics

Ideal hydrodynamics reproduces v2 relatively well

Below pT~2 GeV, matches v2 and spectra to ~20-30%

Appealing picture:

Nearly perfect fluid with local thermal equilibrium established at <~1 fm with a soft equation of state containing a QGP stage

STAR Preliminary

Hydro calculations: Kolb, Heinz and Huovinen

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Score board status of hydrodynamic models
Score board: status of hydrodynamic models

  • Hadronic + QGP hydro reproduces features of v2(pT) of p, K, p

  • Require early thermalization (ttherm<1fm/c) + high einit > 10 GeV/fm3

  • Detailed discrepancies between models and with experiment

Source average

Table courtesy of PHENIX

Quark Matter at High Density/Temperature James Dunlop ICHEP04


How unique and robust is hydro account in detail
How unique and robust is hydro account in detail?

P. Kolb, J. Sollfrank, and U. Heinz, Phys. Rev. C. C62 054909 (2000).

How does sensitivity to EOS in hydro calcs. compare quantitatively to sensitiv-ity to other unknown features: e.g., freezeout treatment (compare figures at right), thermaliz’n time, longitudinal boost non-invariance, viscosity?

  • What has to be changed to understand HBT (below), and what effect will that change have on soft EOS conclusion?

Sharp freezeout  dip

Hydro+RQMD  no dip?

Hydro vs. STAR HBT Rout/Rside

Teaney, Lauret & Shuryak

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Partonic energy loss in dense matter jet tomography
Partonic energy loss in dense matter:“Jet Tomography”

Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,…

Multiple soft interactions:

Gluon bremsstrahlung

Opacity expansion:

  • Strong dependence of energy loss on gluon density glue:

    • measure DE color charge density at early hot, dense phase

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Partonic energy loss via leading hadrons
Partonic energy loss via leading hadrons

Binary collision scaling

p+p reference

Energy loss  softening of fragmentation  suppression of leading hadron yield

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Control system p p collisions
Control system: p+p collisions

p-p PRL 91 (2003) 241803

Good agreement

with NLO pQCD

Parton distribution functions

Fragmentation functions

To generalize for nuclei:

fa/N(xa,Q2,r) 

fa/N(xa,Q2) .

Sa/A(xa,r) .

tA(r)

Nuclear modification to structure function (shadowing, saturation, etc.)

Nuclear thickness function

p0 well described by pQCD and usual fragmentation functions

p0

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Suppression of inclusive hadron yield
Suppression of inclusive hadron yield

RAA

Au+Au relative to p+p

RCP

Au+Au central/peripheral

PRL 91, 172302

  • central Au+Au collisions: factor ~4-5 suppression

  • pT>5 GeV/c: suppression ~ independent of pT

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Pqcd in au au direct photons
pQCD in Au+Au? Direct photons

( pQCD x Ncoll) / background Vogelsang/CTEQ6

( pQCD x Ncoll) / (background x Ncoll)

[w/ the real suppression]

[if there were no suppression]

Au+Au 200 GeV/A: 10% most central collisions

Preliminary

pT (GeV/c)

[]measured / []background = measured/background

Perturbative calculation for direct photons works in central Au+Au

Quark Matter at High Density/Temperature James Dunlop ICHEP04


P 0 r aa s systematics
p0 RAAsSystematics

Vitev, nucl-th/0404052

Cronin and parton energy loss at lower s

Reasonable agreement with 62.4 GeV result.

larger Cronin effect

gluon dN/dy = 850 (rather than 1100)

No large surprises in energy dependence

PHENIX Preliminary

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Jets at rhic
Jets at RHIC

jet

parton

nucleon

nucleon

Find this……….in this

p+p jet+jet ([email protected])

Au+Au ??? ([email protected])

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Jets and two particle azimuthal distributions
Jets and two-particle azimuthal distributions

trigger

p+p  dijet

  • trigger: highest pT track, pT>4 GeV/c

  • Df distribution: 2 GeV/c<pT<pTtrigger

  • normalize to number of triggers

Phys Rev Lett 90, 082302

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Azimuthal distributions in au au
Azimuthal distributions in Au+Au

?

Au+Au peripheral

Au+Au central

pedestal and flow subtracted

Phys Rev Lett 90, 082302

Near-side: peripheral and central Au+Au similar to p+p

Strong suppression of back-to-back correlations in central Au+Au

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Real tomography geometry of medium
“Real” tomography: geometry of medium

?

STAR Preliminary, nucl-ex/0407007

  • Au+Au: Away-side suppression is larger in the out-of-plane direction compared to in-plane

  • Geometry of dense medium imprints itself on correlations

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Hard sector quantitative indication of early gluon density
Hard Sector: Quantitative Indication of Early Gluon Density

PHENIX

  • Inclusive hadron and away-side cor-relation suppression in central Au+Au, but not in d+Au, clearly establish jet quenching as final-state phenomenon, indicating very strong interactions of hard-scattered partons or their fragments with dense, dissipative medium produced in central Au+Au.

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Questions for parton energy loss models
Questions for Parton Energy Loss Models

  • pQCD parton energy loss fits to observed central suppression  dNgluon/dy ~ 1000 at start of rapid expansion, i.e., ~30-50 times cold nuclear matter gluon density.

  • Large extrapolation needed to take into account time-dependent expansion

  • How sensitive is this result to:

    • assumptions of factorization in-medium and vacuum fragmentation following degradation

    • treatments of expansion and initial-state cold energy loss preceding hard collision?

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Gluon saturation a qcd scale for initial gluon density early thermaliz n mechanism
Gluon Saturation: a QCD Scale for Initial Gluon Density + Early Thermaliz’n Mechanism?

PHOBOS, PRC 65, 061901R

BRAHMS, nucl-ex/0403005

sNN = 130 GeV Au+Au

  • Does the high initial gluon density inferred from parton E loss fits demand a deconfined initial state? Can QCD illuminate the initial conditions?

  • Assuming initial state dominated by g+g below the saturation scale (con-strained by HERA e-p), Color Glass Condensate approaches ~account for RHIC bulk rapidity densities  dNg/dy ~ consistent with parton E loss.

  • Rapidity dependence of RdA consistent, though questions about uniqueness

  • Remaining questions about robustness and uniqueness of approach

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Unusual behavior in baryons
Unusual behavior in baryons Early Thermaliz’n Mechanism?

Large enhancement in baryons at intermediate pT

Not explainable in vacuum fragmentation framework

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Intermediate p t hints of relevant degrees of freedom
Intermediate p Early Thermaliz’n Mechanism?T: hints of relevant degrees of freedom

Clear separation into two classes: baryons and mesons

Apparent scaling with number of constituent quarks in final-state hadron

Explained currently by recombination/coalescence of constituent quarks at hadronization

If better established, direct evidence of the degrees of freedom relevant at hadronization, and the existence of collective flow at the constituent quark level

STAR Preliminary, nucl-ex/0403032

v2/nq

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Jet like correlations at intermediate p t
Jet-like correlations at intermediate p Early Thermaliz’n Mechanism?T

PHENIX Preliminary, nucl-ex/0408007

  • jet partner equally likely for trigger baryons & mesons

  • Same side: slight decrease with centrality for baryons

  • Larger partner probability than pp, dAu

  • Away side: partner rate as in p+p confirms jet source of baryons!

  • “disappearance” of away-side jet for both baryons and mesons

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Questions for coalescence models
Questions for Coalescence Models Early Thermaliz’n Mechanism?

Duke-model recomb. calcs.

Duke-model recomb. calcs.

  • Can one account simultaneously for spectra, v2 and di-hadron  correlations at intermediate pT with mixture of quark recombination and fragmentation contributions? Do observed jet-like near-side correlations arise from small vacuum fragmentation component, or from “fast-slow” recombination?

  • Are thermal recomb., “fast-slow” recomb. and vacuum fragment-ation treatments compatible? Double-counting, mixing d.o.f., etc.?

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Five observations
Five Observations Early Thermaliz’n Mechanism?

Ideal hydro

Early thermalization + soft EOS

Statistical model

Quark recombination constituent q d.o.f.

…suggest appealing QGP-based picture of RHIC collision evolution, BUT invoke 5 distinct models, each with own ambiguities, to get there.

u, d, s equil-ibration near Tcrit

pQCD parton E loss

CGC

Very high inferred initial gluon density

Very high anticipated initial gluon density

Quark Matter at High Density/Temperature James Dunlop ICHEP04


Summary
Summary Early Thermaliz’n Mechanism?

  • RHIC has made major advances in runs 1-3, leading to an appealing picture of bulk, dense, highly interacting matter.

  • Extended reach in energy density appears to reach simplifying conditions in central collisions -- ~ideal fluid expansion; approx. local thermal equilibrium.

  • Extended reach in pT gives probes for behavior difficult to access at lower energies – jet quenching; ~constituent quark scaling.

  • However: In the absence of a direct “smoking gun” signal of deconfinement revealed by experiment alone, a QGP discovery claim must rest on the comparison with a promising, but still not yet mature, theoretical framework. In this circumstance, clear predictive power with quantitative assessments of theoretical uncertainties are necessary for the present appealing picture to survive as a lasting one.

Quark Matter at High Density/Temperature James Dunlop ICHEP04


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