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March 16-19Chunbin Yang Elliptic Flow Without Using Hydrodynamics Chunbin Yang Hua-Zhong Normal University Wuhan, China Done with R.C. Hwa University of.

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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:

1 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

2 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

3 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

4 March 16-19Chunbin Yang v 2 scaling

5 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

6 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 , (2001).

7 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

8 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

9 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.

10 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.

11 March 16-19Chunbin Yang Recombination model Distributions depend on b and  v2v2

12 March 16-19Chunbin Yang Bulk partons pions Bulk+Ridge partons

13 March 16-19Chunbin Yang v2v2

14 March 16-19Chunbin Yang Thermal pions only p T <1.5 GeV/c Small p T region

15 March 16-19Chunbin Yang

16 March 16-19Chunbin Yang T’ p =0.35(1-0.5c) GeV

17 March 16-19Chunbin Yang T p ’’=2.37GeV

18 March 16-19Chunbin Yang

19 March 16-19Chunbin Yang

20 March 16-19Chunbin Yang At intermediate P T Soft partons Hard partons Energy loss proportional to L L depends on azimuthal angle Fit spectra to fixed parameter Thermal-shower recombination

21 March 16-19Chunbin Yang Hard parton with momentum K originated with higher k’=k+Δk

22 March 16-19Chunbin Yang 0-10% Determine parameter

23 March 16-19Chunbin Yang

24 March 16-19Chunbin Yang

25 March 16-19Chunbin Yang

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28 March 16-19Chunbin Yang

29 March 16-19Chunbin Yang

30 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

31 March 16-19Chunbin Yang Thank you!


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