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Collective motion of Xe-Xe collision at CSR energy

Collective motion of Xe-Xe collision at CSR energy. Xie Fei, Wu Kejun, Liu Feng ccnu Institute of Particle Physics. Outline. Motivation Result and discussion Centrality selection Baryon density evolution Collective flow Thermalization and m T spectra Summary. 1. Motivation.

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Collective motion of Xe-Xe collision at CSR energy

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  1. Collective motion of Xe-Xe collision at CSR energy Xie Fei, Wu Kejun, Liu Feng ccnu Institute of Particle Physics

  2. Outline • Motivation • Result and discussion • Centrality selection • Baryon density evolution • Collective flow • Thermalization and mT spectra • Summary

  3. 1. Motivation Matter Compression: Vacuum Heating: Deconfinement CSR energy High Baryon Density -- low energy collisions -- neutron starquark star High Temperature Vacuum -- high energy collisions -- the Big Bang

  4. HIRFL-CSR SFC: up to 10 AMeV SSC: up to 100 AMeV North Building 2# SSC SFC CSRe CSRm 1. Motivation The Heavy Ion Research Facility in Lanzhou (HIRFL) Cooler Storage Ring (CSR) CSRm: 500AMeV~1000AMeV Status and Prospects of HIRFL Experiments Hushan Xu

  5. ETF Phase I(External Target Facility – Phase I) Z.G. Xiao SQM2008 • For RIB Physics mainly •  detectors:4 segmented Clover detectors • ToF Wall:3, 2 layers of BC408 bars, 30 bars/layer, readout fromboth ends with PMT (R7525) • Neutron Wall:14 layers, 18 paddles/layer, readout from both ends with PMT (R7724); BC408 only for the first two layers, sampling type (BC408+Fe) for the others • MWDC:6, with conventional technique

  6. Key part！！ ETF Phase II • New Detectors • -ball • (CsI(Tl) array • MWPC • (inside dipole) • Si-strip array • (inside dipole) • TPC? • (at target region) • Possible Physics • For RIB Physics • For EoS of asymmetry nuclear matter • For high baryon density matter

  7. 2.1 Centrality selection • Two methods: • The multiplicity of forward neutrons with polar angle θ < 15◦ in the laboratory frame. • 2. The multiplicity of charge particles Nch with mid-rapidity • linear dependence of the impact parameter b

  8. 2.2 Baryon density R 5.7fm 6.3fm Short (b -b) 5.8fm Long (t -t) 9.4fm

  9. z y x 2.3 Collective flow(1) v1 flow parameter:

  10. 2.3 Collective flow(2) In ART model: Mean field: are all functions of K Soft : K=201MeV Stiff : K=377MeV Cascade : no mean field Flow parameter is sensitive to EOS.

  11. 2.3 Collective flow(3) Jean-Yves Ollitraulta arXiv:nucl-ex/9802005 v1 12 Feb 1998 At CSR energy region, around 500~1000MeV/u, it has very rich flow information, i.e. collision dynamics information. CSR energy

  12. 2.3 Collective flow(4) F will get the maximum at about b/bmax=0.2 for different elements bmax Cu 9fm Xe 12fm Pb 14fm

  13. 60~80% 40~60% 10~30% 0~10% The Charge Multiplicity Nch 2.4 Thermalization and mT spectra(1)

  14. 2.4 Thermalization and mT spectra(2) (a) proton (b) pion

  15. Summary • We can use forward Neutron or Nch to determine the collision centrality • v1 flow is sensitive to the EOS and system size • Anisotropy flow reach its extremum at CSR energy range. The turnings contain rich dynamic information. This energy region is well worth studying for flow. • Radial collective motion is stronger at central collisions.

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