Presentation on theme: "March 16-19Chunbin Yang Elliptic Flow Without Using Hydrodynamics Chunbin Yang Hua-Zhong Normal University Wuhan, China Done with R.C. Hwa University of."— Presentation transcript:
March 16-19Chunbin Yang Elliptic Flow Without Using Hydrodynamics Chunbin Yang Hua-Zhong Normal University Wuhan, China Done with R.C. Hwa University of Oregon, USA March 17,2008,Hungary
March 16-19Chunbin Yang Outline QGP, flow and hydrodynamics Quark recombination and flow V 2 at low p T V 2 at intermediate p T Summary
March 16-19Chunbin Yang Formation of QGP at RHIC Strong suppression of pion spectrum in central Au+Au collisions Absence of opposite jets Quark number scaling of v 2
March 16-19Chunbin Yang Results on single-particle distributions from hydro Kolb & Heinz, QGP3 0 =0.6 fm/c (RHIC 130, 200), 0 =0.8 fm/c (SPS 17) RHIC 130 GeV
March 16-19Chunbin Yang Agree with data for p T <1.5GeV/c possible only if 0 ~0.6 fm/c Huovinen, Kolb, Heinz, Ruuskanen, Voloshin Phys. Lett. B 503 58, (2001).
March 16-19Chunbin Yang Conventional wisdom Azimuthal anisotropy can be understood in terms of hydrodynamical flow for p T <1.5 GeV/c It requires fast thermalization. 0 =0.6 fm/c high pressure gradient at early time before the spatial asymmetry disappears leads to momentum space asymmetry: v 2 >0
March 16-19Chunbin Yang Alternative approach must be sensitive to the initial configuration must be able to describe the bulk behavior For p T <1.5 GeV/c (the region that hydro claims success) we consider semi-hard scattering: Semi-hard parton q T ~ 2-3 GeV/c ( 0.1 fm/c) can have significant effect on thermal partons for p T <1.5 GeV/c. Ridges
March 16-19Chunbin Yang The ridge would not be there without a semi-hard scattering, but it does not appear as a usual jet. Ridges of low p T hadrons are there, with or without triggers, so long as there are semi-hard partons near the surface to generate enhanced thermal partons. Ridgeology Ridges are the recombination products of enhanced thermal partons stimulated by semi-hard scattering near the surface. At low p T there can be ridges without Jets (peaks). A ridge without any significant peak on top.
March 16-19Chunbin Yang | | < = cos -1 (b/2R) Each scattering sends semi-hard partons in random directions. At any given on average, the jet direction is normal to the surface. Recoil partons thermalize the bulk medium. Initial configuration Thermalization of partons takes time, but the average direction of each ridge is determined at initial time.
March 16-19Chunbin Yang Recombination model Distributions depend on b and v2v2
March 16-19Chunbin Yang Bulk partons pions Bulk+Ridge partons
March 16-19Chunbin Yang Summary Ridge plays an important role in flow Features of elliptic flow can be reproduced by the recombination model Quark number scaling violation of v 2 is due to the difference between flows of thermal and shower partons