Outline First of all, there’s too much data!! BRAHMS PHOBOS PHENIX Focus on some recent results and analyses BRAHMS PHOBOS PHENIX STAR Low, Intermediate, High-pt Can we understand it? Can at least some of it be synthesised? Spectra Flow

Particle Spectra in Au+Au, STAR |y|<.5 STAR Preliminary Hydro inspired “Thermal” Fits (input to Blast-Wave parameterization) (T, bt) = (170 MeV, 0.6c) Large transverse flow component in central collisions.

Hydrodynamics  Equation of State Low pt, 99.5% of particles are below 2 GeV. Hydrodynamics describes bulk particle momentum distributions Hydro is limit of zero mean free path…early phase dominated by strong interactions? Calculations  too long a system lifetime (still work to do) Enormous initial pressure, but decouples quickly (~10 fm/c)

Spectra at large y, BRAHMS. Radial flow decreases at large rapidity. Boost invariant region is only about 1 unit wide! 3-D hydro y=0 Thermal fit T = 0.53 T = 138. MeV y=3 Thermal fit T = 0.42 T = 140 MeV

Charged hadrons at large h, PHOBOS T. Hirano Hydrodynamics: Mid-rapidity data is well described, but larger rapidity is not.

Particle Ratios and Statistical Models Statistical models do a very good job. Values Tch are very close to expected Tcrit from lattice. However, this alone cannot prove a phase transition nor that the system is thermal; but coupled with agreement from hydrodynamics (spectra and v2), evidence starts to increase…

Intermediate pt, spectra for various masses Yield of p (L) similar to p(K) at ~3 GeV, flow effect for heavier particle/baryon?

Compare with scaling by Ncoll… K0s and p0 show suppression at 2-3 GeV, p and L do not… strong radial flow for heavier particles?

Particles with Similar Mass Differ at low pt, similar at ~3 GeV Reflection of Flow? Rescattering? Recombination? Rescattering has effect on other observables: resonances! (See Patricia’s talk)

Wealth of data! It is very important to try to understand as much of the combined measurements as possible Under a single framework! Many times, predictions work for observable A but fail for observable B. Need a coherent picture! Some recent ideas: Hydro-inspired Blast-wave (won’t go into it) Recombination+Fragmentation Single Freeze-out

Fragmentation + Recombination Lopez, Parikh, Siemens, PRL 53 (1984) 1216: Net charge and baryon number fluctuations [Asakawa, Heinz, BM, PRL 85 (2000) 2072; Jeon, Koch, PRL 85 (2000) 2076] Balance functions [Bass, Danielewicz, Pratt, PRL 85 (2000) 2689] Recombination / coalescence [Fries, BM, Nonaka, Bass, nucl-th/0301087; Greco, Ko, Levai, nucl-th/0301093; Molnar, Voloshin, nucl-th/0302014] Fragmentation Recombination Bass et al. nucl-th/0306027

F+R: Model assumptions at low pt, quarks and antiquarks recombine into hadrons locally “at an instant”: hadron momentum P is much larger than average momentum Δp2 of the internal quark wave function of the hadron; features of the parton spectrum are shifted to higher pt in the hadron spectrum parton spectrum has thermal part (quarks) and a power law tail (quarks and gluons) from pQCD.

Does it fit the measured spectra? Teff = 350 MeV blue-shifted temperature pQCD spectrum shifted by 2.2 GeV R.J. Fries, B. Müller, C. Nonaka, S.A. Bass; PRL 90 202303 (2003)

For identified particles…p, K

…p, f, L, X, W

Ratios vs pt

High pt suppression. Reproduces charged hadron suppression, and flavor dependence. Prediction, quenching for protons above 6 GeV, where fragmentation starts to dominate

What about v2?

Does v2 reflect partonic flow? P. Sorensen (UCLA – STAR) Quark v2 Recombination model suggests that hadronic flow reflects partonic flow (n = number of valence quarks): Provides measurement of partonic v2 ! See also: Lin & Ko, PRL 89 (2002) 202302; Molnar & Voloshin, nucl-th/0302014

Identified Particle Spectra at RHIC @ 200 GeV BRAHMS: 10% central PHOBOS: 15% PHENIX: 5% STAR: 5% Feed-down matters !!!

Single freeze-out model, Tch = Tkin? Very nice feature, include feeddown in the calculations. Describe spectra and ratios vs pt and vs centrality well Supports the use of thermal approach to heavy ion collisions If Tch=Tkin, very explosive expansion! W. Broniowski and W. Florkowski, PRC 65 064905 (2002), for 130 GeV A. Baran, W. Broniowski, W. Florkowski nucl-th/0305075 for 200 GeV ratios and spectra.

High-pt: Latest news from the d+Au run From cover of PRL 91 (2003) 072302 Phobos 072303 Phenix 072304 Star 072305 Brahms In Au+Au, suppression of high-pt hadrons and of away side jet, not seen in d+Au. Final state effect…consistent with the production of dense matter!!

Summary & Conclusions All 4 RHIC experiments have continued their outpour of measurements. Low pt spectra, hydrodynamic fits, statistical models taken together yield support (albeit don’t prove) to a high density thermalized phase. Still trouble in the longitudinal direction (HBT, v2 vs y) We are beginning to see more theoretical efforts that encompass various observables! That is good! Spectra, flow, correlations. Would like to understand in one picture, pt, y and centrality dependence. Fragmentation + Recombination: aplicability of the recombination regime to 3-6 GeV, fragmentation dominates at a higher pt than one naïvely expected. v2 of hadrons reflects v2 of constituent quarks (? and !) High-pt spectra and correlations: suppression of hadrons and away-side jet is a final state effect.