Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX Masahiro Konno (Univ. of Tsukuba) for the PHENIX　Collaboration Contact e-mail: konno@rcf.rhic.bnl.gov Motivation Baryon/Meson difference in yield and emission pattern Hadron production in relativistic heavy ion collisions Phenix preliminary Hadronization Interactions in the medium Low-pT (soft) Thermal emission Quark recombination Thermalization Collective flow High-pT (hard) Jet fragmentation Hard scattering Jet quenching p/+ - There are multiple hadronization mechanisms at intermediate pT (2~5 GeV/c). The relative contributions and particle-type dependence are not yet fully understood. p/- p/ in p+p (√sNN = 62.4, 200 GeV) Outstanding question: (Anti-)proton enhancement observed/confirmed at pT = 2~5 GeV/c Larger than expected from jet fragmentation (measured in pp, e+e-) p/ ( p/) ratios turn over at 2~3 GeV/c , and fall towards the ratio in p+p collisions - Indicating a transition from soft to hard at intermediate pT - What pT does hydrodynamic contribution exist up to? - Quark recombination process is really necessary? - Can we separate hadron radial flow and quark radial flow ? Focusing on: - The ratio is controlled by the initial size of the created systems (~Npart) - Transverse energy density is a connection key between different √sNN << Proton and antiproton production >> - Sensitive to collective flow due to its relatively large mass - Indicator of baryon number transport at lower energies (Hadronization) Blast wave model: Quark recombination model: Simple parameterization at low pT (<1 GeV/c) How about ambiguity due to velocity profile? => Several velocity profile tested; n=1 is best case One of the hadron production mechanisms Recombination of thermal quarks Separation of soft/hard components (extrapolation because of thermal distribution) Two component model: Transverse velocity Freeze-out temperature Soft: Blast-wave fit (thermal + radial flow) Hard: p+p spectra, Nbin scaling, constant suppression factor Ref: PRC 68 (2003) 044902 PRL 90 (2003) 202302 PRC 70(2004) 024905 - Consistent description for pions and protons - Trying to explain soft/hard crossover Phenix preliminary Fraction of soft/hard components p+p spectra - Cross point (S=H) vs. pT - p Blue: data Red: data - Hydro B.W. line In a simple recombination picture, radial flow cannot be distinguished between hadron and quark phases p Intermediate pT: Hard pions vs. Soft protons Separation in v2 Separation in p/ Hard v2 is not zero. It may be caused by jet quenching. Phenix preliminary ++ - (0) v2 (BW p)/(BW ) BW v2 + p/+ Blue: data Red: data - B.W. (BW p)/(real ) - Blue: data v2 Red: estimated hard v2 p+p v2 p/- Central Peripheral Central Peripheral Radial flow is one of the explanations of baryon enhancement. It’s significant. PHENIX detector (Two-arm magnetic spectrometer, ||<0.35) Both soft/hard yields (dN/dy) are not scaled with Npart. Multiple scattering, energy loss should be considered. Separation in yield (dN/dy/(Npart/2)) Aerogel Cherenkov (PID) EM Calorimeter (PID) , pT>0 GeV/c , pT>2 GeV/c , pT>4 GeV/c TOF (PID) Pad Chambers (tracking) Drift Chamber (momentum meas.) Black: sum Blue: soft Red: hard p, pT>0 GeV/c p, pT>2 GeV/c p, pT>4 GeV/c Particle Identification Aerogel Cherenkov (n=1.011) proton ID up to 7 GeV/c Time of Flight (~120 ps) proton ID up to 4 GeV/c Veto for proton ID m2 distributions (3.5-4.0 GeV/c) p - Origin of baryon enhancement: It’s transverse radial flow which is pushing particles to higher pT Contribution of soft component at higher pT The enhancement and freeze-out properties are controlled by system size The next question: What’s the relation of hadronic and partonic radial flow? K+ Conclusion + Clear proton line up to high pT INPC, June/2007, Tokyo