The 9th Japan-China Joint Nuclear Physics Symposium (JCNP 2015)
Osaka, Japan, Nov. 7-12, 2015
Isovector reorientation of deuteron in the field of
heavy target nuclei
Zhigang Xiao (肖志刚)
Tsinghua University, Beijing, China（清华大学）
Li Ou （欧立）
Guangxi Normal University, China （广西师范大学）
Contents
1 Introduction to the nuclear Symmetry Energy
2 Orientation of Deuteron in nuclear reactions
3 Isovector reorientation of d on heavy target nuclei
4 Summary
Symmetry Energy
Energy cost to convert protons to neutrons in nuclear medium
 2 2 3
L

2
E (  ,  )  E0 (  )   Esym (  )  aV   
  ...    Esym    ...
18
162
3


2
:Compressibility
L.W. Chen, C.M. Ko and B.A. Li, Phys. Rev. C72, 064309 (2005); C76, 054316 (2007).
Esym
Relevance of Esym() in astrophysics and nuclear physics
2


L

2
2
3
2
E (  ,  )  E0 (  )   Esym (  )  aV      ...    Esym    ...
18
162
3


:Compressibility
•
•
•
•
•
Esym
Proton fraction
M-R relation
c for D-Urca
Transition density
……
Phy. Rep. 442(2007) 109;
NPA777(2006)479
PRC76(2007),015801;
PRC75(2007) 015801
PRC74 (2006),035802;
Phy. Rep. 411(2005) 325;
Astro. J. 676 (2008) 1170
PLB 642, 436 (2006)
......
Astrophysical Connection
A shopping list for sub-saturation density
Esym()
At sub-saturation densities
 Isospin scalaring and isospin
fractionaiton (MSU…)
 Isospin diffusion (MSU …)
 n/p ratio of fast and preequilibrium nucleons (MSU …)
 N/Z of the emitted fragments
(LNS, TAMU, MSU, HIRFL …)
 GMR strength (ND/RCNP …)
 HBT correlation function (KVI,
MSU, HIRFL …)
 Pb Polarizability(RCNP)…. ….
S0 = 32±3 MeV
L = 55±25 MeV
Slope=L
S0
30
0.5
1
 /0
Topical issue on the Symmetry Energy
EPJA 50(2014) 29
EPJA 50(2014) 37
Is there any other probes?
Nucleon induced reaction:
For proton, isovector potential being attractive, the scattering angle  will be larger with a
stronger symmetry energy.
Angular distribution in peripheral n/p-induced scattering carries the information of
symmetry energy.
Nucleon induced scattering --- a new probe
Shall it work well?
How do you have the neutron beam?
What about to bind n and p?
 Deuteron!
Polarization Effect in d-induced reaction
• Oppenheimer proposed first
Favored
p
n
Target
Un-favored
n
p
Target
Coulomb polarization
(Reorientation)
• J. R. Oppenheimer et al., Phys. Rev. 48, 500 (1935)
• E. O. Lawrence et al., Phys. Rev. 48, 493(1935)
Polarization effect in breakup reactions
• 17F polarization on target: PLB 681 (2009) 22–25
p
16O
Dynamical Polarization
Target
A nature question arises now……
• Coulomb force ,1 for proton and 0 for neutron, leads to Coulomb polarization (reorientation),
characterized by the moving away of proton.
• Isovector force, attractive for proton and repulsive for neutron, shall leads to isovector
reorientation, characterized by the modification of the direction of the relative motion.
n
p
Target
Isovector force act on p and n like a torque
 Reorientation effect
• If this effect is detectable, it should be sensitive
to the isovector potential ( symmetry energy!)
Calculation
framework
IQMD
Initialization of Deuteron
Initialization:
• dnp=3r (r<0.25)
• pn, pp randomly sampled
• Bounded longer than 100 fm/c
• <r2>1/2 = 2.10.2 fm
Define the observable in breakup events
• How can we find an observable?
 Break up kinetics
Correlation angle
First attempt: not that successful
Isospin Effect is shown up, but not
as sufficient as one would expect.
What else?
Initial polarization of Deuteron
Random orientation of the incident deuteron smears the isovector reorientation effect!
We need initial polarized deuteron beam! （PV 1, PT1）
V. Baryshevsky, A. Rouba
Physics Letters B 683 (2010) 229–234
A surprise
• When the incident deuteron is polarized, the isovector re-orientation effect is
significant!
• Effect is sensitive to the impact parameter.
Figure out an observable
• The angular distribution is an observable.
• Fit the slope at cos=0
Last question: How do we select the nucleons?
• Collision contribution is a contamination
• Kinetic feature characterizes the direct breakup events
• Only one 2-D cut is used in the data analysis.
The sensitivity is kept!
Density range of sensitivity
b=6 fm
b=7 fm
• What density region is this
observable sensitive on?
Density range < 0.5 0
Just as what we expect!
b=7.5 fm
Summary
• A novel reorientation effect of deuteron attributed to isovector interaction in the nuclear field
of heavy target nuclei has been investigated for the first time.
• The correlation angle of nucleons from the breakup of polarized deuteron, depends sensitively
on the isovector potential but insensitively on the isoscaler potential.
• In terms of sensitivity and cleanness, the breakup reactions induced by polarized deuteron
beam at about 100 MeV/u provide a more stringent constraint to the symmetry energy at
subsaturation densities.
For details, Please refer to
PRL 115, 2015, to be published Nov. 20
Welcome to
6th international symposium on nuclear symmetry energy
(NuSym2016)
Tsinghua University, Beijing, Jun. 13-17, 2016
Thank you for your attention!