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Fragmentation mechanism and enhanced mid-rapidity emission for neutron-rich LCPs

第十四届全国核结构大会， 2012 年 4 月 14 日 浙江 湖州. Fragmentation mechanism and enhanced mid-rapidity emission for neutron-rich LCPs. Yingxun Zhang( 张英逊 ). 中国原子能科学研究院. Colloborator : Chengshuang Zhou 周承双 (CIAE,GXNU), Jixian Chen 陈佶贤 (CIAE,GXNU), Ning Wang 王宁 (GXNU), Zhuxia Li 李祝霞 (CIAE).

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Fragmentation mechanism and enhanced mid-rapidity emission for neutron-rich LCPs

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  1. 第十四届全国核结构大会， 2012年4月14日 浙江 湖州 Fragmentation mechanism andenhanced mid-rapidity emission for neutron-rich LCPs Yingxun Zhang(张英逊) 中国原子能科学研究院 Colloborator: Chengshuang Zhou 周承双(CIAE,GXNU), Jixian Chen 陈佶贤(CIAE,GXNU), Ning Wang 王宁 (GXNU), Zhuxia Li 李祝霞 (CIAE)

  2. Features of Intermediate energy HICs • Multifragmentation • <15 intermediate mass fragments (IMFs) 1， Mechanism (two scenario) 2 Thermal process Dynamical process 1, Y(A) ~ A-t 1, Y(A) ~ A-t 2, E_kin independent of frag. size 2, E_kin independent of frag. size 3, bimodality (???) 3, bimodality Data support Dynamical process, but not finished!!

  3. H.Jaqaman et al. PRC27(1983)2782 • 2， related to the Liquid-Gas Phase transition and asy-EoS • Heavy Ion Collisions • large regions of r, T, d , measure the N/Z ratios of the emitted particles (n/p ratios, isospin diffusion, t/He3, N/Z ratios of IMFs, flow, pi-/pi+, ……) compare with the prediction from the transport model, in which the different symmetry potential can be used. the symmetry energy information can be extracted. Indirectly! (depends on models)

  4. Constraints on symmetry energy at subsaturatoin density Tsang,Zhang, et al.,PRL102(2009) ImQMD (DR, Ri, R7) 50MeV/A, 35MeV/A, Danielewicz, et.al S0：the values of S(r) energy at r0 L： the slope of S(r) energy at r0 Ksym: the curvature of S(r) energy at r0 S0~31 ± 4 (MeV) L~60 ± 23 (MeV) PDR(Pb), A.Klimkiewicz LWChen, BALi, et al,(Skin, Ri) Problem: Although overlap, but different in detail!

  5. How to further understand the fragmentation mechanism and constrain the asy-EOS with HICs? More DATA and observable !! Z Kohley, PRC83,044601 (2011) Ni,Zn+Ni,Zn @ 35AMeV QT LCP beam LCP, QP Significant difference !! Dynamical points: binary and ternary fragmentation dominate the reaction process ?? Statistical decay of QP ?? (Kohley， 2011)

  6. t He4 He6 >1, enhanced mid-rapidity emission d He3 p Aims: 1, Why diff. ?? 2, Equilibrium?? 3, Symmetry energy?? Analyze with ImQMD05

  7. ImQMD05 (Improved QMD model developed at CIAE) Detail of code: Zhang, et alPR C71 (05) 024604, PR C74 (06) 014602, PRC75,034615(07)., PL B664 (08) 145, PRC85(2012)024602 • the mean fields acting on nucleon wavepackets are derived fromSkyrme potential energy density functional H=T+U+U_coul EOS potential energy density functional: Surface symmetry energy term

  8. Isospin dependent nucleon-nucleon cross sections are adopted, the medium corrections are Cugnon, et al., Nucl.Instr.Meth.Phys. B111, 215(1996) h depend on the beam energy Well reproduce the data of charge distribution, direct flow, elliptical flow and stopping power (30-400AMeV), DR(n/p), Ri (at 50AMeV, 35AMeV), Ri(y), et.al.,

  9. Properties of LCP emission g_i=0.5 or 2.0 1, LCP mainly came from neck region 2, Yield of LCP depend on the density dependence of symmetry energy 64Ni+64NI, 35AMeV, b=4fm 3, Calculation with soft symmetry energy case predict larger yield for d, t,He3, He4, He6 4, t,He3, He4, He6, Dynamical emission. Better to probe the symmetry energy.

  10. Fragmentation mechanism Zhang/Zhou/Chen, et.al, Submitted QT beam QP 1, binary, ternary fragmentation events are ~50%; and mult-fragmentation events are ~50%. more transparency. 2, binary, ternary fragmentation events; increase the yield at middle rapidity 3, 50% multi-fragmentationevents; decrease the yield at proj/targ region Binary: M(Z>3)=2, Ternary: M(Z>3)=3, Multi: M(Z>3) >=4

  11. Rapidity distribution for LCP Zhang/Zhou/Chen, et.al, Submitted 1, Calculations with stiff symmetry energy case well reproduce rapidity distribution for LCPs. 2, Width of rapidity distribution for LCP decrease with mass increasing 3, Difference at backward. The decreased efficiency for detection of LCPs at backward region.

  12. Enhanced emission of LCPs and constraints on S(r) Zhang/Zhou/Chen, et.al, Submitted 1, reproduce the R^mid_yield for 64Zn reaction system 2, LCP data definitely rule outgamma_i<0.5, it improve the previous constraints g_i=[0.45,0.95]. 3, Underestimate the R^mid_yield for neutron-rich reaction system, should be further understand.

  13. Conclusion • Dynamical process is the main reason on well describing the rapidity distribution for LCP. Our results suggest that reaction system is more transparency than that predicted by SMF approaches. Binary and ternary events, 50%; multi-fragmentation events: 50%. • Binary and ternary fragmentation events tends to produce LCPs at middle rapidity, but multi-fragmentation events tends to produce at forward and backward region. • The data of rapidity distribution for LCP and their ratio R^mid_yield definitely rule out the g_i=0.5, and it improve the previous constraints on symmetry energy g_i=(0.45,0.95).

  14. Thanks for your attention!!

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