Interesting RHIC Observations 1. Suppression of high pT hadrons 2. Increased baryon production at high pT 3. Large v2 values and the pT dependence 4. Strange Baryon Production 5. HBT measurement – short emission duration Suppression of High pT Charged Hadrons Used UA1 p+p 200 GeV data (pT<6 GeV/c) as reference 1.0 YieldAA RAA= Strong Suppression Nbin Yieldpp in central Au+Au 1.0 N-Binary Scaling 1.0 in peripheral Au+Au Preliminary sNN = 200 GeV Similar suppression pattern for p0 and for 130 GeV Au+Au data and also observed by PHENIX Issues in High pT Hadron Suppression 1. Uncertainties in p+p reference data 2. Collision geometry – Npart and Nbinary 3. Gluon shadowing – we do not know the gluon structure function of nuclei yet 4. Cronin effect – partonic multiple scattering, lack of theoretical understanding: pA experiment 5. Theoretical calculation of parton energy loss (low Q2 region) (exp DE ~ E ?) 6. Jet quenching or “jet abortion” 7. Heavy quark jet – energy loss different ! Large Proton to Pion Ratio at pT > 2 GeV/c PHENIX Preliminary PHENIX Preliminary Au+Au at sqrt(sNN) =200GeV Au+Au at sqrt(sNN) =200GeV Baryon yield ~ meson yield Very different from string fragmentation !!! Issues on High pT Baryon Production 1. Why baryon/meson ratio > 1 at pT > 2 GeV/c? 2. Hydrodynamical expansion vs exotic production dynamics 3. High mass meson production vs pions 4. Baryon and meson production at really high pT (> 4-5 GeV/c?) (KS and L) 5. At what pT pQCD will set in (p/pion ratio decreases with pT) ? Increased High Mass Particles with Strangeness Issues in Elliptic Flow 1. Dynamics responsible from geometrical anisotropy to momentum anisotropy 2. Magnitude of v2? Validity of hydrodynamic picture. 3. pT dependence of v2: why saturation? 4. Particle dependence of v2: does or doesn’t depend on final state hadronic cross section? 5. V2 for resonance particles? Intriguing v2 as a function of pT • Statistical errors only • Finite v2 up to 12 GeV/c in mid-peripheral bin Issues in Strange Baryon Production 1. Dynamics of hyperon production: enhancement of high mass hyperons 2. Baryon production and multi-gluon dynamics 3. Net baryon number at mid-rapidity and dynamics for baryon number transport 4. Mechanism for transport initial baryon number to multiply-strange hyperons 5. Comparison of pp--AA L Production from Au+Au Collisions L, L @ 130 GeV “Large” Yield of X Particles vs L Dn/dy of Strange Baryons Centrality 0-5% 5-10% 10-20% 20-35% 35-75% L 17.0+-0.4 13.0+-0.3 10.1+-0.2 5.9 +-0.2 1.61+-0.05 anti-L 12.0+-0.3 9.6+-0.3 7.4+-0.2 4.6+-0.1 1.26+-0.04 Centrality 0-10% 10-25% 25-75% X 2.30+-0.09 1.29+-0.12 0.28+-0.02 anti-X 1.89+-0.08 1.08+-0.11 0.24+-0.02 Relative large yield of strange baryons !! Issues in HBT Measurement • Is there a mixed-phase?
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