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Hadronization of a QGP via recombination

Hadronization of a QGP via recombination. Kang Seog Lee. Chonnam National University. Introduction – recombination model Dynamic recomination calculation : Hydrodynamic evolution of QGP + + Hadronization via recombination in mixed phase + Hadronic rescattering by URQMD

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Hadronization of a QGP via recombination

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  1. Hadronization of a QGP via recombination Kang Seog Lee Chonnam National University • Introduction – recombination model • Dynamic recomination calculation : Hydrodynamic evolution of QGP + + Hadronization via recombination in mixed phase + Hadronic rescattering by URQMD • Results • Summary and Outlook collaborators: • S. Bass • B. Müller • C. Nonaka

  2. Recombination : long history High Energy Physics Phenomenology: • K.P. Das & R.C. Hwa, Phys. Lett. B68, 459 (1977) Quark-Antiquark Recombination in the Fragmentation Region • description of leading particle effect • T. Ochiai, Prog. Theo. Phys. 75, 1184 (1986) • E. Braaten, Y. Jia & T. Mehen, Phys. Rev. Lett. 89, 122002 (2002) • R. Rapp & E.V. Shuryak, Phys. Rev. D67, 074036 (2003) Heavy-Ion Phenomenology: • T. S. Biro, P. Levai & J. Zimanyi, Phys. Lett. B347, 6 (1995) ALCOR: a dynamical model for hadronization • yields and ratios via counting of constituent quarks • R.C. Hwa & C.B. Yang, Phys. Rev. C66, 025205 (2002) • R. Fries, B. Mueller, C. Nonaka & S.A. Bass, Phys. Rev. Lett. 90 • R. Fries, B. Mueller, C. Nonaka & S.A. Bass, Phys. Rev. C68, 044902 (2003) • V. Greco, C.M. Ko and P. Levai, Phys. Rev. Lett. 90 Anisotropic flow: • S. Voloshin, QM2002, nucl-ex/020014 • Z.W. Lin & C.M. Ko, Phys. Rev. Lett 89, 202302 (2002) : AMPT • D. Molnar & S. Voloshin, nucl-th/0302014 Jin-Hui Chen’s talk

  3. Recombination+Fragmentation Model R.J. Fries, C. Nonaka, B. Mueller & S.A. Bass, PRL 90 202303 (2003) ; PRC68, 044902 (2003) basic assumptions: • at low pt, the quarks and antiquark spectrum is thermal and they recombine into hadrons locally “at an instant”: • features of the parton spectrum are shifted to higher pt in the hadron spectrum • at high pt, the parton spectrum is given by a pQCD power law, partons suffer jet energy loss and hadrons are formed via fragmentation of quarks and gluons

  4. Hadron Spectra I

  5. Elliptic Flow: Recombination vs. Fragmentation • high pt: v2 for all hadrons merge, since v2 from energy-loss is flavor blind • charged hadron v2 for high pt shows universal & limiting fragmentation v2 • quark number scaling breaks down in the fragmentation domain

  6. Parton Number Scaling of v2 • in leading order of v2, recombination predicts: P. Soerensen, UCLA & STAR @ SQM2003 • smoking gun for recombination • measurement of partonic v2 !

  7. Hadron Ratios vs. pt

  8. hadronic phase and freeze-out QGP and hydrodynamic expansion initial state pre-equilibrium hadronization Model

  9. Recombination of thermal quarks I • wave functions are best know in the light cone frame. • for a thermal distribution:

  10. Recombination of thermal quarks II • hadronization hypersurface : mixed phase • Energy conservation during the recombination • For a cell at hadronization, is the energy available for hadronization where is the volume fraction of QGP phase. • In a hydrodynamic cell, i, hadronization rate in direction is proportional to

  11. Recombination of thermal quarks III • depends only on the quark masses and is independent of hadron mass. • Since , there are 4 cases for mesons and 8 cases for baryons. • Inside a group, relative abundances are assumed to be (Ci : degeneracy factors) e.g.

  12. Recombination of thermal quarks IV • After hadronization, hadronic rescattering is simulated by URQMD !

  13. Results & Comparison to Data • hadron spectra • hadron ratios – coming soon • RAA – coming soon • elliptic flow – coming soon

  14. Summary & Outlook Hadronization of a QGP via Recombination: • Hydrodynamic evolution of a QGP until mixed phase - reasonable for a perfect fluid • hadronization via quark recombination - quark number scaling of elliptic flow, … • hadronic rescattering by URQMD - different chemical and thermal freeze-out No problem of freeze-out prescription !!! issues to be addressed in the future: • results are coming soon. • comparison with statistical hadronization • combine with viscous hydrodynamics or parton cascade

  15. Statistical Model vs. Recombination • in the Statistical Model, the hadron distribution at freeze-out is given by: • If , recombination is identical to SM!

  16. Parton Number Scaling of Elliptic Flow • in the recombination regime, meson and baryon v2 can be obtained from the parton v2 in the following way: • neglecting quadratic and cubic terms, one finds a simple scaling law:

  17. Recombination: Pro’s & Con’s Pro’s: • for exponential parton spectrum, recombination is more effective than fragmentation • baryons are shifted to higher pt than mesons, for same quark distribution • understand behavior of protons! Con’s: fragmenting parton: ph = z p, z<1 recombining partons: p1+p2=ph • recombination violates entropy conservation • gluons at hadronization need to be converted

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