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Zhao-Qing Feng ( 冯兆庆 ) Institute of Modern Physics, CAS ( 中国科学院近代物理研究所，兰州 )

Probing the high-density behavior of the symmetry energy from pion emission in heavy-ion collisions. Zhao-Qing Feng ( 冯兆庆 ) Institute of Modern Physics, CAS ( 中国科学院近代物理研究所，兰州 ). Outline. Motivation for investigating symmetry energy in heavy-ion collisions

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Zhao-Qing Feng ( 冯兆庆 ) Institute of Modern Physics, CAS ( 中国科学院近代物理研究所，兰州 )

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  1. Probing the high-density behavior of the symmetry energy from pion emission in heavy-ion collisions Zhao-Qing Feng (冯兆庆) Institute of Modern Physics, CAS (中国科学院近代物理研究所，兰州) IWND09

  2. Outline Motivation for investigating symmetry energy in heavy-ion collisions Improved isospin dependent quantum molecular dynamics (ImIQMD) model Pion emission in heavy-ion collisions in 1A GeV region as probes of symmetry energy Summary IWND09

  3. IWND09

  4. Symmetry energy per nucleon: L.W. Chen, C.M. Ko, and B.A. Li PRC72,064309(2005);PRC76, 054316(2007) IWND09

  5. Z.H. Li et al., PRC74, 047304(2006) Dieperink et al., PRC68, 064307(2003) BHF IWND09

  6. I. Vidana et al., arXiv: 0907.1165 IWND09

  7. Promising probes of the Esym(ρ) in Nuclear ReactionsB.A. Li, L.W. Chen, C.M. Ko, Phys.Rep.464(2008) 113-281, L.W. Chen’s Talk in Lanzhou Aug 2009 IWND09

  8. Improved isospin dependent quantum molecular dynamics model (ImIQMD or IQMD08) • ‘Quantum molecular dynamics model’ (QMD) by Aichelin et al., Phys. Rep 202 (1991) 233, PRL 58 (1987) 1926 • Based on isospin dependent quantum molecular dynamics model(IQMD, Refs: L.W. Chen et al.,PRC58(1998)2283, PLB459(1999)21; F.S. Zhang et al., PRC60(1999)064604) • Potential energy terms (two and three body terms, surface and surface symmetry terms, effective mass, symmetry energy term) in ImIQMD model are derived from Skyrme energy density functional • Nucleon’s fermionic nature is embodied by using a phase space constraint method • Shell effect is considered by a phenomenological approach in description of heavy-ion fusion reactions (Z.Q. Feng et al., NPA750(2005)232, NPA802(2008)91) • Inelastic channels in nucleon-nucleon collisions are also included, such as NNN(1232), NNNN*(1440) • Experimental elastic and inelastic cross sections are parameterized in the ImIQMD model IWND09

  9. Simple introduction of ImIQMD model Time evolutions for baryons: IWND09

  10. Symmetry energy in ImIQMD model from Skyrme energy-density functional Also expressed as with s=0.5 (soft), s=1. (linear, IQMD) and s=2. (hard) with Csym=32 MeV Time evolutions for pions: Reaction channels for inelastic nucleon-nucleon collisions IWND09

  11. NN elastic and inelastic cross sections(Chin.Phys.Lett.26(2009)062501) IWND09

  12. ImIQMD parameters with and without momentum dependent (Z.-Q. Feng et al., Nucl.Phys.A802(2008)91, Chin.Phys.Lett.26(2009)062501) Parameterswith momentum dependent with =1.57 MeV and=500 c2/GeV2(PRL 58 (1987) 1926) IWND09

  13. IWND09

  14. Pion as probes of symmetry energy at supra-saturation density IWND09

  15. Transverse momentum distribution with parameter SLy6 but soft and hard symmetry energy IWND09

  16. -/+ at different Skyrme parameters and stiffness of the symmetry energy SLy6 IWND09

  17. ImIQMD: arXiv:0904.2990 IBUU04: PRL102(2009)062502 IWND09

  18. UrQMD: W. Trautmann et al., arXiv:0907.2822 Model of Di Toro group PRL97(2006)202301 stiffer Esym(20) IWND09

  19. J.Phys.G 31 (2005) S741-757 Transport theories for heavy-ion collisions in the 1 A GeV region IWND09

  20. Summary • Symmetry energy at supra-saturation density is investigated by analyzing the -/+ ratios in heavy-ion collisions within the framework of the ImIQMD model • Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (/0)s with s=2 • High-density behavior of the symmetry energy is still an open problem, which should be supplemented by more experimental data. Different models (IBUU04, ImIQMD, UrQMD, etc) or observables predict different stiffness of the symmetry energy. A consistent results of various models should be required. IWND09

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