1 / 18

Manuel Calder ó n de la Barca S á nchez

ISMD ‘02, Alushta, Ukraine Sep 9, 2002. Manuel Calder ó n de la Barca S á nchez. Understanding “Bulk” Matter in HI collisions. 99.5%. Studying Matter: Global Observables N ch ,  E T  ,  p T   e , S, … Particle Yields & Ratios  T ch , m B , m S , … Particle Spectra

brasen
Download Presentation

Manuel Calder ó n de la Barca S á nchez

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. ISMD ‘02, Alushta, Ukraine Sep 9, 2002 Manuel Calderón de la Barca Sánchez

  2. Understanding “Bulk” Matter in HI collisions 99.5% Studying Matter: • Global Observables Nch, ET, pT  e, S, … • Particle Yields & Ratios  Tch, mB, mS, … • Particle Spectra  Tfo, flow, stopping, … STAR preliminary

  3. Nch: Centrality Dependence at RHIC (SPS) _ pp PHOBOS Au+Au |h|<1 200 GeV 130 GeV Au+Au 19.6 GeV preliminary (preliminary) • Everything counts: • Nch|h=0 described nicely by Kharzeev-Nardi (hard + soft) • Nch scales with Npart

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

  5. pT 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 GeV to verify (or falsify)

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

  7. Ratios at RHIC I : vs. p^ All experiments: p-/p+ 1 K-/K+ 0.95 Does p/p also stay constant, or does it begin falling?

  8. Ratios at RHIC II: vs. y BRAHMS 200 GeV At mid-rapidity: Net-protons: dN/dy  7 proton yield: dN/dy  29  ¾ of all protons from pair-production

  9. 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 mB/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(2ms/T) p/p driven by mB ~ exp(-2mB/T) ms = ms (mB) since <S> = 0 BUT: Holds for y  0 (BRAHMS y=3)

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

  11. Boost-Invariance at RHIC ? p- p- • dN/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 dN/dy •  Boost invariance only achieved in small region |y|<0.5

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

  13. Interpreting the Spectra • The shape of the various particle spectra teach us about: • Kinetic freeze-out temperatures • Transverse flow • The stronger the flow the less appropriate are simple exponential fits: • Hydrodynamic models (a la Heinz/Kolb/Shuryak/Huovinen/Teaney) • Hydro inspired parameterizations (Blastwave) • Blastwave parameterization: • Ref. : E.Schnedermann et al, PRC48 (1993) 2462 (modifications by Snellings, Voloshin) • Very successful in recent months • Spectra • HBT (incl. the Rout/Rside puzzle) • Flow spectra (p) HBT b

  14. Blastwave Fits at 130 & 200 GeV Results depend slightly on pT coverage STAR: Tfo ~ 100 MeV bT ~ 0.55c (130) & 0.6c (200) PHENIX: Tfo ~ 110 MeV (200) bT ~ 0.5c (200) 200 GeV Fits M. Kaneta (STAR)

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

  16. Does it flow? Fits to Omega mT spectra STAR preliminary RHIC SPS/NA49 bT 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 v2 of 

  17. 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*, L, X, W) •  Thermal fits to spectra are not enough to make the point. • To discriminate between different models they have to prove their validity by describing: • Spectra (shape & yield) • Correlations (HBT, balance function, etc.) • Flow • Only then we can learn …

  18. Conclusions • Flood of data from SPS & RHIC • new probes • correlations between probes • higher statistics & precision • Models (Generators) are behind • The majority of models in RHI fail already describing global observables (possible exception AMPT) • Many models describe “A” well but fail badly at “B”  can still be useful but limited scope • 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 • Agreement between thermal fits to particle spectra and ratios + flow makes a very strong case for thermalization of matter created at RHIC

More Related