Download 重离子碰撞约束对称能中的相关问题 - 中国科学院大科学装置理论物理

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 A1 / 3  aC Z ( Z  1 ) A4 / 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   12.5r / r0 
2/3
 17.5r / 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!