Spectra Physics at at RHIC Spectra Highlights from

Spectra Physics at at RHIC : : Spectra Highlights from 200 Ge. V data Highlights ISMD ‘ 02, Alushta, Ukraine Sep 9, 2002 Manuel Calderón de la Barca Sánchez

Understanding “Bulk” Matter in HI collisions Studying Matter: Global Observables Nch, ET , p. T e, S, … u 99. 5% Particle Yields & Ratios Tch, m. B, m. S, … u Particle Spectra Tfo, flow, stopping, … u STAR preliminary 2

Nch: Centrality Dependence at RHIC (SPS) PHOBOS Au+Au |h|<1 200 Ge. V 130 Ge. V _ pp Au+Au 19. 6 Ge. V (preliminary) preliminary Everything counts: • Nch|h=0 described nicely by Kharzeev-Nardi (hard + soft) • Nch scales with Npart 3

ET / Nch from SPS to RHIC PHENIX preliminary Independent of centrality PHENIX preliminary Independent of energy Surprising fact: SPS RHIC: increased flow, all particles higher p. T still ET / Nch changes very little Does different composition (chemistry) account for that? 4

p. T of Charged Hadrons from SPS to RHIC increase only ~2% STAR preliminary Saturation model: J. Schaffner-Bielich, et al. nucl-th/0108048 D. Kharzeev, et al. hep-ph/0111315 Many models predict similar scaling (incl. hydro) Need data around s = 70 Ge. V to verify (or falsify) 5

Ratios Huge amount of results from all 4 RHIC experiments: • systematic studies of: -/ +, K-/K+, p/p, / , /p, K/ , /h, , , f K, K*/K, … u many as function of p. T, Npart u at s of (20), 130, and 200 Ge. V u Problem: with and without feed-down correction BRAHMS large y coverage and reach to high p. T PHENIX reach to high p. T STAR multi-strange baryons 6

Ratios at RHIC I : vs. p^ All experiments: - + 1 K-/K+ 0. 95 Does p/p also stay constant, or does it begin falling? 7

Ratios at RHIC II: vs. y BRAHMS 200 Ge. V At mid-rapidity: Net-protons: d. N/dy 7 proton yield: d. N/dy 29 ¾ of all protons from pair-production 8

K-/K+ and p/p from AGS to RHIC Slightly different view of statistical model. Becattini calculation using statistical model: T=170, gs=1 (weak dependency) vary m. B/T K+/K- and p/p K- /K+=( p/p)1/4 is a empirical fit to the data points K- K+ driven by ms ~ exp(2 ms/T) p/p driven by m. B ~ exp(-2 m. B/T) ms = ms (m. B) since <S> = 0 BUT: Holds for y 0 (BRAHMS y=3) 9

Rapidity Spectra: Boost-Invariance at RHIC ? D. Ouerdane (BRAHMS) 10

Boost-Invariance at RHIC ? - - • d. N/dy of pions looks boost-invariant BUT • change in slopes for rapidity already from 0 1 • BRAHMS (J. H. Lee): no change in proton slope from y = 0 3 BUT increase in d. N/dy Boost invariance only achieved in small region |y|<0. 5 11

Identified Particle Spectra at RHIC @ 200 Ge. V BRAHMS: 10% central PHOBOS: 15% PHENIX: 5% STAR: 5% Feed-down matters !!! 12

Interpreting the Spectra The shape of the various particle spectra teach us about: u Kinetic freeze-out temperatures u Transverse flow The stronger the flow the less appropriate are simple exponential fits: u Hydrodynamic models (a la Heinz/Kolb/Shuryak/Huovinen/Teaney) u Hydro inspired parameterizations (Blastwave) Blastwave parameterization: u u Ref. : E. Schnedermann et al, PRC 48 (1993) 2462 (modifications by Snellings, Voloshin) spectra ( ) Very successful in recent months l l l Spectra HBT (incl. the Rout/Rside puzzle) Flow HBT b 13

Blastwave Fits at 130 & 200 Ge. V Results depend slightly on p. T coverage 200 Ge. V STAR: Tfo ~ 100 Me. V b. T ~ 0. 55 c (130) & 0. 6 c (200) PHENIX: Tfo ~ 110 Me. V (200) b. T ~ 0. 5 c (200) Fits M. Kaneta (STAR) 14

What flows and when? STAR preliminary F. Wang <p. T> prediction with Tth and <b> obtained from blastwave fit (green line) <p. T> prediction for Tch = 170 Me. V and <b>=0 pp no rescattering, no flow no thermal equilibrium and appear to deviate from common thermal freeze-out Smaller elast? Early decoupling from expanding hadronic medium? Less flow? What about partonic flow? 15

Does it flow? Fits to Omega m. T spectra STAR preliminary RHIC SPS/NA 49 b. T is not well constrained ! • What do we now about elast of and ? • May be it flows, and may be they freeze out with the others • Maybe and are consistent with a blastwave fit at RHIC • Need to constrain further more data & much more for v 2 of 16

Other Attempts: The Single Freeze-Out Model Single freeze-out model (Tch=Tfo) (W. Broniowski et. al) fit the data well (and reproduce f, K*, , , ) Thermal fits to spectra are not enough to make the point. To discriminate between different models they have to prove their validity by describing: u Spectra (shape & yield) u Correlations (HBT, balance function, etc. ) u Flow Only then we can learn … 17

Conclusions • Flood of data from SPS & RHIC u new probes u correlations between probes u higher statistics & precision • Models (Generators) are behind u The majority of models in RHI fail already describing global observables (possible exception AMPT) u Many models describe “A” well but fail badly at “B” can still be useful but limited scope l We learn more by combing various pieces and putting them into context § Thermalization, Chemical and Kinetic Freeze-out Conditions, and System Dynamics can only be studied (and are studied) using all the pieces together u Agreement between thermal fits to particle spectra and ratios + flow makes a very strong case for thermalization of matter created at RHIC 18