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2015强子物理与核物理前沿研讨会 Frontiers in Hadron and Nuclear Physics (FHNP’15) 重离子碰约束对称能中的相关问题 张英逊(Yingxun Zhang) 中国原子能科学研究院(CIAE) 国科大, 1月10日,怀柔 Outline 1, Nuclear equation of state and symmetry energy 2, Progress and Challenges on the constraints of symmetry energy 3, Influence of L, fI on HIC observables • isospin diffusion • single Y(n)/Y(p) and Double Y(n)/Y(p) ratios spectra for free nucleons • Coalescence invariant Y(n)/Y(p) and DR(n/p) • comparison to the data 4, Summary and outlook Symmetry energy and EOS Nuclei E( A, Z ) / A av as A1 / 3 aC Z ( Z 1 ) A4 / 3 as ( N Z )2 /( N Z )2 pair Isospin asymmetric nuclear matter, EOS Symmetry energy E r , E r , 0 S r 2 O( 4 ) S0: symemtry energy coefficient L: slope of density dependent of symmetry energy Ksym: curvature of density dependent of symmetry energy S(r) (MeV) Density dependent of symmetry energy Importance of the Nuclear Symmetry Energy in Nuclear and Astrophysics Heavy ion collisions in the Fermi energy regime; multifragmentation Esym rB MeV) Asy-stiff Asy-soft 0 Light cluster correlations at very low density 1 Nuclear structure (neutron skin thickness, Pygmy DR, IAS) Slope of Symm Energy From Hermann’s talk rB/r0 2 supernovae 3 supernova simulations covers large range of thd. conditions Strategies for constraining the symmetry energy • Astrophysical measurements • Nuclear structure • Heavy Ion Collisions large regions of r, T, , measure the N/Z ratios of the emitted particles (n/p ratios, isospin diffusion, t/He3, N/Z ratios of IMFs, flow, pi/pi+, ……) predictions from the transport model, in which the different symmetry potential can be used. QMD, BUU,AMD, SMF, …… the symmetry energy information can be extracted. Indirectly! (transport models) HIC observables: n/p ratios and isospin diffusion, …… BALi, et al., PRL78(1997)1644 Tsang et al., PRL 92 (2004) 062701 Projectile 124Sn Famiano, et al., PRL97,0522701(2006) Target 112Sn Isospin Diffusion; low r, Ebeam Y(n)/Y(p); t/3He, p+/p- Yingxun Zhang et al., PLB664(2008)145 LWChen, et al., PRL72(2005)064309 Constraints on the density dependence of symmetry at subsaturation density M.B.Tsang, Y.X.Zhang, et al., PRL102,122701(2009) (222 cites) Detailed comparison with data by varying i Esym r 12.5r / r0 2/3 17.5r / r0 i Consistent c2 analysis of these observables within ImQMD model provides with gamma_i=[0.45,0.95] M.B.Tsang, Yingxun Zhang, et.al., PRL2009 Lattimer, EPJA 50 (2014) 40 Consensus on symmetry energy have been obtained at subsaturation density, Challenges on constraining the symmetry energy 1. How to understand the difference on the constraints on the symmetry energy? 2. Constraints at very low density 3. Constraints at supra-normal density with HICs Symmetry energy at r<0.05ro, T<10 MeV is dominated by correlations and cluster formation Esym(n)/Esym(n0) J.B. Natowitz et al, PRL 104 (2010) 202501 MDI, NN-ND, threshod, …… 差别的来源 • 不同模型采用相同的有效核力不同 • Vsym(r,k)=Vloc(r)+Vnlc(r,k) • …… 更多观测量来约束理论上的不确定性 •理论提供更多同位旋敏感观测量 • 新的实验测量 输运模型中采用与结构研究中相同的有效核力 New version of ImQMD Y.X. Zhang, M.B.Tsang, Z.X. Li, HLiu, PLB(2014) Changes: 考虑动量相关势对重离子碰撞观测量的影响 density dependent of symmetry energy from Skyrme interaction in HF: two-body term three-body term Mom. dependent Density dependent Zhang, et al., PRC85,024602(2012) L.Ou, Z.X.Li, Y.X.Zhang, M.Liu, PLB697(2011) Momentum dependent symmetry potential->effective mass splitting R. Chen et al., PRC 85, 024305 (2012). Effective mass splitting E-mass K-mass M_n*>m_p* M_n*=m_p* M_n*<m_p* ????? Influence of Skyrme force to HIC observables K0 = 230 ± 20MeV, S0 = 32 ± 2MeV, m*_s=0.7+/-0.1 different L and n/p effective mass splitting. Select four parameter sets Para. Rho_0 E0 K0 Q0 J L Ksym m*_s m*_n/m*_p SLy4 0.16 -15.97 229.91 363.11 32 46 -120 0.69 <1 SkI2 SkM* 0.158 0.16 -15.78 -15.77 240.93 216.61 339.70 386.09 33 30 104 71 46 -156 0.68 0.79 <1 >1 Gs 0.158 -15.59 237.29 348.79 31 93 0.78 >1 14 Small L Large L m_n*<m_p* SLy4 (L=46MeV) SkI2 (L=104MeV) m_n*>m_p* SkM* (L=46MeV) Gs (L=93MeV) Corresponding density dependence of symmetry energy , and the symmetry potential as a function of nucleon energy Zhang, Tsang, Li, Liu,, PLB732,186(2014) • The Larger the L is, the smaller the symmetry energy at <rho0 is. • The larger the Usym is, the larger the n/p ratio is • Isospin diffusion and isospin transport ratios as a function of rapidity A=124Sn, B=112Sn Isospin diffusion occurs only in asymmetric systems A+B, and diffusion ability depends on the symmetry energy and n/p effective mass splitting. Zhang, Tsang, Li, Liu,, PLB732,186(2014) For m*n<m*p, the isospin diffusion process is accelerated due to larger Lane potential at subsaturation density. Ri=(2X-XAA-XBB)/(XAA-XBB) In absence of isospin diffusion R=1 or R=-1, R~0 for isospin equilibrium Ri(SLy4, L=46MeV, m*_n<m*_p)<Ri(SkM*, L=46MeV, m*_n>m*_p) < Ri(SkI2, L=104MeV, m*_n<m*_p)<Ri(Gs, L=93MeV, m*_n>m*_p) Ri is more sensitive to L than n/p effective mass splitting. Isospin diffusion R(n/p) and DR(n/p) 50AMeV, b=2fm Zhang, Tsang, Li, Liu,, PLB732,186(2014) Mn*>mp*??? D.D.S.Coupland, et al., arXiv:1406.4546 • 新观测量的探索,出射轻粒子角分布各向异性 Ar+Au轻粒子动力学发射 Colin, PRC Qianghua Wu, Yingxun Zhang, Z.G.Xiao, et.al. PRC(2015) in press 4, Summary and outlook 1, Developed a new version of ImQMD which can accommodate the Standard Skyrme interaction in parameters. It can bridge the reaction and structure study by using same EDF. 2, The Ri and Ri(y) support the SLy4 and SkM* interactions, they have L=46MeV, it is close to the results from neutron skin analysis. 3, Questions? For neutron-rich dense matter, 1) effective mass splitting ? 2) isospin-independent momentum dependent interaction in the transport model? … Collaborators: 李祝霞, M.B.Tsang, P.Danielewicz, W.G.Lynch, D.D.S.Coupland, R.Hodges, H.Liu, Qianghua Wu, Zhigang Xiao, Rensheng Wang, Yan Zhang,王宁 Thanks for your attention!