1. Institute of Modern Physics, CAS
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)
Aug 22-25
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
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3. Aug 22-25
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4. Symmetry energy per nucleon:
L.W. Chen, C.M. Ko, and B.A. Li
PRC72, (2005); PRC76, (2007)
Aug 22-25
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5. Z.H. Li et al., PRC74, (2006)
Dieperink et al., PRC68, (2003)
BHF
Aug 22-25
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6. I. Vidana et al., arXiv:
Aug 22-25
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7. Promising probes of the Esym(ρ) in Nuclear Reactions B. A. Li, L. W
Promising probes of the Esym(ρ) in Nuclear Reactions B.A. Li, L.W. Chen, C.M. Ko, Phys.Rep.464(2008) , L.W. Chen’s Talk in Lanzhou Aug 2009
Aug 22-25
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
Aug 22-25
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9. Simple introduction of ImIQMD model
Time evolutions for baryons:
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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
Aug 22-25
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11. NN elastic and inelastic cross sections (Chin. Phys. Lett
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12. ImIQMD parameters with and without momentum dependent (Z. -Q
ImIQMD parameters with and without momentum dependent (Z.-Q. Feng et al., Nucl.Phys.A802(2008)91, Chin.Phys.Lett.26(2009)062501)
Parameters with momentum dependent with =1.57 MeV and =500 c2/GeV2 (PRL 58 (1987) 1926)
Aug 22-25
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13. Aug 22-25
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14. Pion as probes of symmetry energy at supra-saturation density
Aug 22-25
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15. Transverse momentum distribution with parameter SLy6 but soft and hard symmetry energy
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16. -/+ at different Skyrme parameters and stiffness of the symmetry energy
SLy6
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17. ImIQMD: arXiv:
IBUU04: PRL102(2009)062502
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18. UrQMD: W. Trautmann et al., arXiv:0907.2822
Model of Di Toro group PRL97(2006)202301
stiffer
Esym(20)
Aug 22-25
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19. Transport theories for heavy-ion collisions in the 1 A GeV region
J.Phys.G 31 (2005) S
Transport theories for heavy-ion collisions in the 1 A GeV region
Aug 22-25
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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.
Aug 22-25
IWND09