Probing the nuclear symmetry energy with HIC: an overview of different transport models used in China
NuSym2013, FRIB/NSCL, East Lansing, USA, July 22-26, 2013
W. J. Xie(谢文杰), J. Su(苏军), F.S. Zhang(张丰收)College of Nuclear Science and TechnologyBeijing Normal University, Beijing, ChinaTel: +86-10-6220 5602,+86-10 6220 8252-806Fax: +86-10-6223 1765E-mail: [email protected]://lenp.bnu.edu.cn/hkxyweb/zhangfengshou.htm
M. Liu(刘敏): Guangxi Normal UniversityB. A. Bian(卞宝安): Jiangnan UniversityZ.Q. Feng(冯兆庆): Institute of Modern Physics, CASL. W. Chen(陈列文): Shanghai Jiaotong University
Contributions also by:
Outline1.Introduction
2.Different transport models used in China
3.Observables for symmetry energy
Nuclear dynamics at intermediate and high energies by IQMD and IBL
ProjectileTarget
?
What happened?
Size?Lifetime?
Shape?
T Detectors
dense, hot, and asymmetric nuclear matter
Equation of StateOf Nuclear Matter
E(,T
From compound nuclei ( 0, T1-2 MeV,)
hot nuclei( 0,T>5 MeV),
highly excited nuclei ( 30,T>5 MeV)
asymmetrical highly excited nuclei
( 2-30,T>5 MeV, >0)
Physical indications IEOS
0, T > 0, >0
E(, T, ) = ?
MSU, 1996-1998 112,124Sn(40MeV/nucl.)+112,124Sn
isospin effects in multifragmentation 58Fe(45-105 MeV/nucl.)+58Fe,
58Ni(45-105 MeV/nucl.)+58Ni,
disappearance of isospin effects in multifragmentation
Physical indications and challenges 0, T > 0, >0E(, T, ) = ?
Important to production of RIB &Neutron Stars !!!
G. J. Kunde et al., Phys. Rev. Lett. 77, 2897 (1996)
Quantum molecular dynamics model (QMD)The QMD model represents the many body state of the system and thus contains correlation effects to all orders. In QMD, nucleon i is represented by a Gaussian form of wave function.
After performing Wigner transformations, the density distribution of nucleon i is:
Improved isospin dependent quantum molecular dynamics model
From QMD model to IQMD model (1997,1998) mean field (corresponds to interactions)
MDISymCoulYuklocz UUUUUU ),(
two-body collisions
pauli blocking
initialization
coalescence model
Uloc : density dependent potential
UYuk: Yukawa (surface) potential
UCoul: Coulomb energy
USym: symmetry energy
UMD: momentum dependent interaction
IQMD model for studying isospin dependence of collective flow, PRC58(1998)2283
Averaged number of IMF <NIMF> as a function ofNC, NLC, and NN (4 analyzing)
Exp data, G. J. Kunde et al., Phys. Rev. Lett. 77, 2897 (1996)
IQMD model for studying isospin dependence of multifragmentation, PRC60(1999)064604
Average n multiplicity <NN>, as afunction of charged-particle multiplicity NC
Exp data, G. J. Kunde et al., Phys. Rev. Lett. 77, 2897 (1996)
Averaged number of IMF <NIMF> as a function of NC, NLC,and NN (4 pre equilibrium emissions)
Exp data, G. J. Kunde et al., Phys. Rev. Lett. 77, 2897 (1996)
IQMD model for studying isospin dependence of radial flow, PLB459(1999)21
Chapter 10:Isospin-Dependent Quantum Molecular Dynamics Model and Its Applications in
Heavy Ion Collisions, F. S. Zhang, L. W. Chen, et al.
PLB319(1993)35PRC51(1995)3201
BUU BLEfor studying nuclear multifragmentation
BLE IBLE for studying isospin effects in nuclear multifragmentation, NPA807(2008)71
Nuclear Multifragmentation,F. S. Zhang and L. X. Ge,
Science Press, Beijing, 1998
Transport models in heavy ion collisions in China, 2011.9(20)
2011.9 Transport models in HIC in China (Huzhou)1. CIAE(YZ Zhuo, ZX LI, XZ Wu, YX Zhang, K Zhao, XH Lu, …)2. ITP(EG Zhao, SG Zhou, …)3. IHEP(B Liu, …)4. IMP(JQ Li, W Zuo, ZQ Feng, GC Yong, …)5. SINAP(YG Ma, DQ Fang…)6. PKU(FR Xu, YX Liu,…)7. TsinghuaU(ZG Xiao, …)8. BNU(JB Bao, FS Zhang, …)9. NJU(ZZ Ren, C Xu,…)10.USTC(Q Wang, …)11.SJTU(LW Chen, ..) 12.FudanU(ZH Li, BR Wei, …)13.SZU(N Wang,…)14.GXNU(N Wang, M Liu, L O, …)15.HNNU(CW Ma, …)16.HUTC(CW Shen, QF Li, …)17.TSTC(YZ Xing, …)18.AYTC(JL Tian, …)19.SHIT (WJ Guo, …)20.JNU(BA Bian, …)
Relativistic Mean-Field predictions
Nuclear Matter Symmetry Energy
: confirm some of isospin-dependent effects, constrain the symmetry energy : even the trend of the symmetry energy with increasing is not constrained
Skyrme Hartree-Fock
Experimental work, M.B. Tsang et al. PRC86, 015803 (2012)
Fuchs, et.al., arXiv:nucl-th/0511070L.W.Chen,et.al., PRC72, 064309 (2005)
Outline1.Introduction
2.Different transport models used in China
3.Observables for symmetry energy
2 Different Transport Models Used in China
2 3/4 2
( )21( ) exp(2 ) 4
ii i
r r
r r ir r p
Quantum Molecular Dynamics like: solve N-body equation of motion
Version: QMD, IQMD, ImQMD, LQMD, CoMD, UrQMD , ……AMD, FMD
2 22
3 2 2
( ) 21( , ) exp ( )( ) 2
i ri
i r
r rf r p p p
Two body collision: occurs between nucleons, i ii i
H Hp rr p
ˆ ˆ ˆ, , , ,r r pp U f f r p t K f K r p t
t m
1( , ) ( ) ( )i if r p r r p pN
Boltzmann-like: f(r,p,t) one body phase space density
Version: IBUU04, BLE,……
Two-body collision: occurs between test part.
2 3/4 2
( )21( ) exp(2 ) 4
ii i
r r
r r ir r p
Quantum Molecular Dynamics like: solve N-body equation of motion
Version: QMD, IQMD, ImQMD, LQMD, UrQMD , ……AMD, FMD
2 22
3 2 2
( ) 21( , ) exp ( )( ) 2
i ri
i r
r rf r p p p
Two body collision: occurs between nucleons
, i ii i
H Hp rr p
2.1Quantum Molecular Dynamics Like Models
Quantum Molecular Dynamics model (J. Aichelin, Phys. Rep. 202 (1991) 233)and Extension of the QMD model (isospin, low and high energies etc.)
Isospin QMD (IQMD) by Nantes group (Hartnack, Aichelin);Ch. Hartnack, R.K. Puri, J. Aichelin, et al., EPJA 1 (1998) 151
IQMD extend by Feng-Shou Zhang, Lie-Wen Chen, et al., BNU, Beijing and Lanzhou); PRC 58(1998)2283, PLB 459(1999)21
Lanzhou QMD (LQMD, IMP CAS, Lanzhou) Z.-Q. Feng et al., NPA 750 (2005) 232, PLB 683 (2010) 140
IQMD in SINAP, Shanghai Yu-Gang Ma et alPRC 84(2001)034612, PRC 83(2011)064607……
QMD (Fuchs et al., Tuebingen Uni, Germany);Improved QMD (ImQMD) by Zhuxia Li, Ning Wang et al., CIAE, Beijing)
PRC 65(2002)064608……
Ultra-relativistic QMD (UrQMD) by Frankfurt groupS.A. Bass et al., Prog. Part. Nucl. Phys. 41 (1998) 255Extend by Qing-Feng Li et al. Huzhou Teachers College, Huzhou
PRC 72(2005)034613
IQMD in BNU
IQMD in SINAP
LQMD in IMP
ImQMD in CIAE
UrQMD in Huzhou
2 3
, i ii i
Coul sym sur MDI
H Hp rr p
H T U U U U U U
QMD
wave function
Hamiltonian equations
two-body collision
Fermionic nature
2 22
3 2 2
( ) 21( , ) exp ( )( ) 2
i ri
i r
r rf r p p p
The N-body phase-space distribution function
, ,, ,
,
N N N N N N NN N N N N
Pauli blocking
phase-space density constraint
Difference in EOS
2 3
, i ii i
Coul MDI sym sur
H Hp rr p
H T U U U U U U
2 2/30 0 0 0( / ) ( / ) ln ( ( / ) 1) /U
5/30 0 0( / ) ( / ) ( / )U g
EOS of symmetric nuclear matter
Soft EOS plus MDI: K=200 MeVHard EOS plus MDI: K=380 MeV
derived directly from the Skyrme energy-density functional3
0 0 0
2 2/3 5/31 2 2 2 0
3 , ,2 8 1 16
3 3(3 5 4 )( )80 2
tt
g t t x t
K=200 ~ 380 MeV
Form 1
Form 2
N. Wang et al. PRC 65.064608; Z.Q. Feng et al., NPA 750 (2005)
J. Aichelin, Phys. Rep. 202 (1991) 233
Difference in symmetry energy3
is the potential energy densitysym sym
sym
U V d r
V
2 1 8/3 2( )symV A B C Y. X. Zhang et al. PhysRevC 74, 014602(2006)
n p
2
0
( )2
isymsym
CV
2 2
0 0
( ) ( )sym sym symV a b
2 3
, i ii i
Coul MDI sym sur
H Hp rr p
H T U U U U U U
Change the density dependence of the symmetry energy
2 2 2
0
( ( ) )2
symsym s
CV
2 2
02sym
sym
CV
or
Form 1
Form 2
Form 3
Form 4
Y. X. Zhang PRC 85, 051602(2012); J. Pu PRC 87, 047603(2013)
N. Wang et al. PRC 85, 034601(2012)
Z. Q. Feng, PRC 87, 064605(2013)
Difference in surface energy
2 3( )2sur
surgU d r
Derived from the Skyrme energy-density functional
Yukawa interaction21 exp( )[exp( ) ( / 4 )
2
exp( ) ( / 4 )]
yYuk ij ij
i j ij
ij ij
VU Lm mr erfc Lm r L
m r
mr erfc Lm r L
2 3
, i ii i
Coul MDI sym sur
H Hp rr p
H T U U U U U U
reflect the surface effects in the finite system
Form 1
Form 2
Aichelin, Phys. Rep. 202 (1991) 233
N. Wang et al. PRC 85, 034601(2012)
Difference in momentum dependent interactions
3 31 2 1 1 2 261
0
4 2 2
1 1 ( ) ( )2 16
1.57[ln(1 5 10 ( ) )]
md N NNU d p d p f p f p
p
Isospin independent
3 3 3, , ,
, , ,0
22
12
( , , ) ln ( ) 1) ( , , )
i jmdi j i j
i j
U C d pd p d r
f r p t p p f r p t
2 3
, i ii i
Coul MDI sym sur
H Hp rr p
H T U U U U U U
Form 1
Form 2 Isospin dependent
Z. Q. Feng, PLB 707,83(2012)
Y. X. Zhang, PRC 85, 051602(2012)
Difference in two-body collisionsNucleon-nucleon cross section in free space
example
difference in parametrizatoinbut fit to the experimental data nn pp np isospin dependent isospin independent
Z.Q. Feng, PhysRevC 85 014604,2012
Difference in in-medium NN cross sections
*
0
(1 ) 0.2freenn nn
** 2( )( ) freenn nn
mm
*
NN 0 NN
NN 0 NN
( , , )
( , , )2=1+ exp( / 0.54568) 1 / 1 (p / ) , p 1GeV/c3
=1+ 0.85 / (1 3.25 ) / 1 (p / ) , p 1GeV/c
1,
freenn nn
p pu
pu
pij
p pu
F u p
F u p F F
F u p
F u p
F F
NN
p >1GeV/c
* freenn medium nnf
Form 1
Form 2
Form 3
Q.F. Li et al.,PRC 62 014606(2000)D. Persram et al.,PRC 65 064611(2002)
G. D. Westfall et al. PRL 71, 1986(1993)
Yuan. PhysRevC 81 034913,2012
Difference in Fermionic nature
1 2
2 2
i 3 2 2,
1 1 min( ,1) 1 min( ,1)
( ) ( )1P = exp exp( ) 2 2
block
Ai k i k
k k i r p
P P P
r r p p
1 (for two nucleon)if
3
3 3
1 (for all nucleon)
( , )i j i j
i
i s s jhj
f
f f r p d rd p
Pauli blocking
phase-space density constraint
block with a probability
33 34 4
3 3 4ij ijhr p
Final states satisfy
2 2 2
2 2
2
2
( ) ( )exp( ) exp( )4
( )exp( )2
i i
i
ifit fit
i
r r L p pL
r ra bL
Final states satisfy
Final states satisfy
Aichelin,Phys. Rep. 202 (1991) 233
Su, Zhang, PhysRevC 87 017602,2013
LI, PhysRevC 64 064612, 2001
Li PhysRevC 83, 044617, 2011
2.2 Boltzmann-like models
ˆ ˆ ˆ, , , ,r r pp U f f r p t K f K r p t
t m
1( , ) ( ) ( )i if r p r r p pN
Boltzmann-like: f(r,p,t) one body phase space density
Version: IBUU04, BLE,……
Two-body collision: occurs between test part.
The differences among the Vlasov, BUU and BL models
F. S. Zhang and L.X. Ge, Nuclear Multifragmentation, Science Press, Beijing,1998A. Ono, J. Randrup, Eur. Phys. J. A 30 (2006) 109
ˆ ˆ ˆ, ,r r pp U f f r p t K f
t m
ˆ ˆ ˆ, ,
, ,
r r pp U f f r p t K f
t mK r p t
ˆ ˆ , , 0r r pp U f f r p t
t m
Vlasov
BUU
BL
IBUU Model for HIC's
, ,r r pp U f f r p t K f
t m
J. Aichelin, G.F. Bertsch, S. Das Gupta, W. Bauer, Bao-An Li, ……
Phase-space distributions f(r, p, t) satify the Boltzmann equation
Solve the Boltzmann equation using test particle methodIsospin-dependent initializationIsospin- (momentum-) dependent mean field potential
Isospin-dependent N-N cross sectionsa. Experimental free space N-N cross section σexp
b. In-medium N-N cross section from the Dirac-Bruecknerapproach based on Bonn A potential σin-medium
c. Mean-field consistent cross section due to m*
Isospin-dependent Pauli Blocking
01 (1 )2 z c symV V V V
Has been extended to IBUU04 by Bao-An Li
IBUU04--- potential1
2
0 0 0 0
, ,3 32 2 2 2
0 0
( , , , , ) ( ) ( ) (1 ) 81
2 2( , ) ( , ) .1 ( ) / 1 ( ) /
2 2( ) 95.98 , ( ) 120.571 1
u l
u l
BU p x A x A x B x x
C Cf r p f r pd p d pp p p p
B BA x x A x x
Isospin- and momentum-dependent potential (MDI)
-30
0
0
0
*
0.16 fm( ) / 16 MeV
( ) 31.6 MeV
K =211 MeV
m /m=0.68
sym
E AE
Das/Gupta/Gale/Li, PRC67,034611 (2003)
MDI Interaction: Gogny
Chen/Ko/Li, PRL94,032701 (2005);Li/Chen,PRC72, 064611 (2005)
IBUU04In-medium Nucleon-nucleon cross sections
2*
*
/ NNmedium free
NN
NN
Neglecting medium effects on the transition matrix
Medium effects: effective mass on the incoming current in initial state and leveldensity of the final state
is the reduced mass of thecolliding pair NN in mediumJ.W. Negele and K. Yazaki, PRL 47, 71 (1981)V.R. Pandharipande and S.C. Pieper, PRC 45, 791 (1992)M. Kohno et al., PRC 57, 3495 (1998)D. Persram and C. Gale, PRC65, 064611 (2002).
1. In-medium cross sections are reduced2. nn and pp cross sections are splitteddue to the neutron-proton effective masssplitting in neutron-rich matterLi/Chen, PRC72 (2005)064611
/medium free
BUU (f) BL( )
ˆ ˆ ˆ, ,r r pp U f f r p t K f
t m
Phase-space distributions f(r, p, t) satify the Boltzmann equation
Isospin- (momentum-) dependent mean field potential
0 1 2 3 40
20
40
60
80
100
Esy
m (M
eV)
/0
soft linear hard supersoft
2 2
0 02
( )( , , ) ( ) ( )
( )
locsymloc
sym
locsym M DI
EU p E
E U
2 2
0
1.57 ln [0.0005 1]MDIU p
2.14 5/3
0 0 0
0
0
( ) 38.9 18.4 3.8
( ) 14.7
( ) 29.4
s
potsym
potsym
sym
E
E
E MeV
B.A. Bian, et al., Nucl. Phys. A807,71(2008); W.J. Xie, et al., Phys. Lett. B 718,1510(2013)
BLThe inelastic channels and cross sections
*
*
, , ,,
NN N NN NN NNN N N
The parameterized cross sections for each channel to produce resonances are obtained in terms of the one-boson exchange model. The resonance lifetime are calculated according to the following figure.
Z.Q. Feng, Phys. Rev. C 82 (2010) 057901; S. Huber, et al. Nucl. Phys. A573, (1994) 587;A.B. Larionov, et al., Phys. Rev. C66,(2002)054604
BL---deal with the fluctuation term
1 1 1 2 2 2 1 2 1 2 1 2, , , , , .K r p t K r p t C p p r r t t
1 2 3 4 1 2 3 4
, ,
12 , 34 1 1 .
L M L M L M L M
L M L M
C r t dpdp Q p Q p C p p
dp dp dp dp Q Q W f f f f
F.S. Zhang et al. Phys. Rev. C 51(1995) 3201, Y. Abe, S. Ayik, et, al. Phys. Rep. 275 (1996)49
20 20 20 2
30 30 30 3
ˆ , , , ,
ˆ , , , .
Q r t t Q r t t tC r t W
Q r t t Q r t t tC r t W
ˆ ˆ ˆ, ,
, ,
r r pp U f f r p t K f
t mK r p t
The fluctuating collision term can be interpreted as a stochastic force acting on density and is characterized by a correlation function,
A projection method is used in the BL model. The fluctuations are projected on a set of low-order multipole moments of the momentum distribution,
Developing processes from BL,IBL to ImIBL
0 0
( , , ) ( ) sym MDIU p U U
0 0
( ) ( )U
0 0
( , ) ( ) symU U
No isospin effects,noinelastic channels
No inelastic channels
Inelastic channels and MDI
F.S. Zhang, Phys. Rev. C51,3201(1995)
B.A. Bian, et al., Nucl. Phys. A807,71(2008)
W.J. Xie, et al., Phys. Lett. B 718,1510(2013)
BL
IBL
ImIBL
*
*
, , ,,
NN N NN NN NNN N N
Outline1.Introduction
2.Different transport models used in China
3.Observables for symmetry energy
How to use those models to probe the nuclear symmetry energy with heavy-ion collisions ?
3.1 At sub-saturation densities (know something) X√
Global nucleon optical potentials from n/p-nucleus and (p,n) reactions
Thickness of n-skin in 208Pb measured using various approaches and sizes of n-skins of unstable nuclei from total reaction cross sections
n/p ratio of FAST, pre-equilibrium nucleons Isospin fractionation and isoscaling in nuclear multifragmentation Isospin diffusion/transport Neutron-proton differential flow Neutron-proton correlation functions at low relative momenta t/3He ratio and their differential flow
3.2 Towards supra-saturation densities (know nothing ) X X π -/π + ratio, K+/K0 ? Neutron-proton differential transverse flow n/p ratio of squeezed-out nucleons perpendicular to the reaction plane Nucleon elliptical flow at high transverse momentum t-3He differential and difference transverse flow
(1)Correlations of multiple observables are important(2) Detecting neutrons simultaneously with charged particles is critical
B.A. Li, L.W. Chen and C.M. Ko, Physics Reports 464, 113 (2008)
Stiff Esym
n/p ratio at supra-normal densities
Central density
2( , ) ( , 0 ) ( )symE E E
B.A. Li et al, Phys. Rev. C 71 (2005) 014608
With the soft symmetry energy then/p ratio of the high-density region can be significantly higher than that of the reaction system.
Based on RBUU model, by calculating the excitation function of pion and kaon ratio, due to the inclusion of delta meson field, a stiffer symmetry energy results in a larger pion and kaon ratios.
stiffer
Based on the IBUU04 model, by calculating the excitation function of pion ratio, a very soft symmetry energy was obtained. A soft symmetry energy results in a larger pion ratio.
FOPI data, W. Reisdorf, et al., Nucl. Phys. A 781, 459 (2007).
Based on the LQMD model, a hard symmetry energy results in a larger pion ratio. A hard symmetry energy was predicted by comparing with the FOPI data.
FOPI data, W. Reisdorf, et al., Nucl. Phys. A 781, 459 (2007).
Based on the improved isospin-dependent BL model, a supersoft symmetry energy is obtained by calculating the excitation functions of pion ratios in comparison with the FOPI data, which is consistent with the IBUU04 calculations.
FOPI data, W. Reisdorf, et al., Nucl. Phys. A 781, 459 (2007).
Bulk nuclear properties from pion yields and other dataH. Jun and P. Danielewicz, by PBUUPBUU: Danielewicz et al., NPA 533, 712 (1991)
1. Molecular dynamics like: N-body approachesCMD, QMD, CoMD,IQMD, LQMD, ImQMD,…
AMD, FMD,…2. Boltzmann-like: 1-body approaches
IBUU (BNV, LV), IBL
Important: Input quantities, numerical treatments,…
How to manage this inconsistency: transport models with the same + the simplest input quantities
Thank you for your attention