Spin-Isospin excitations as quantitative
constraint for the Skyrme tensor force
Chunlin Bai
Department of Physics, Sichuan University
Chengdu, China
Skyrme parameter sets with tensor force
● Tensor effects on the excited states
● GT and SD constraint on the tensor force
● Tests of the constraint
● Recent studies in open-shell nuclei
● Conclusion and outlook
●
KITPC, Jun 14th, 2012
Skyrme parameter sets with tensor force
The tensor terms postulated by Skyrme: Nucl. Phy. 9, 615(1959)
Skyrme parameter sets which include tensor force:
Fl. Stancu et. al, PLB68, 108(1977),
B. A. Brown et. al, PRC74, 061303(2006)
G-Matrix
interaction
T >0,
U>0
G. Colò et. al, PLB644, 227(1977),
D. M. Brink et. al, PRC74, 061303(2006)
Single-particle
energies
T >0,
U<0
T. Lesinski et. al. PRC76, 014312(2007)
Ground state
properties
T ±,
U±
KITPC, Jun 14th, 2012
Tensor effects on GT states
Bai , Sagawa, Zhang, Zhang, Colò, Xu, Phys. Lett. B675, 28(2009)
• Main peak
• Low energy tail
KITPC, Jun 14th, 2012
Tensor effects on Charge-exchange SD
Bai, Zhang, Sagawa,
Zhang, Colò, Xu,
PRL 105,072501(2010)
Exp. From
T. Wakasa et. al.,
PRC 84, 014614(2011)
In T43, T >0, U<0
In SLy5+Tw, T>0, U>0
The SD 1- state is shifted
downward dramatically
by the tensor RPA
correlations.
KITPC, Jun 14th, 2012
Tensor effects in M1 excitations
Cao, Colò, Sagawa, Bortignon, Sciacchitano, PRC 80, 064304 (2009)
KITPC, Jun 14th, 2012
GT and SD constraint on the tensor force
Bai, Zhang, Sagawa, Zhang, Colò, Xu, PRC83,054316(2011);
The exp.main peak energy of SD and GT in 90Zr and
 E th  E exp  2 .5 M eV
208Pb can be the constraints by requiring the condition
● In TIJ family, only T21, T32, T43, and T54 fulfill the condition;
● SD 1- states strongly constrain the value of T;
● Together with SD, GT main peak can be used to constrain value of U.
KITPC, Jun 14th, 2012
Tests of the constraints by SD in 16O
Bai, Sagawa, Colo, Zhang, Zhang,
PRC 84, 044329(2011)
KITPC, Jun 14th, 2012
Tests of the constraints by IVSM in 90Zr and 208Pb
K. Miki et. al., PRL 2012
KITPC, Jun 14th, 2012
Recent studies in open-shell nuclei
HFB+pnQRPA (canonical basis) calculation details:
●
In HFB T=1 pairing is adjusted to reproduce the neutron
pairing gap of 120Sn
●
In HFB cut-off of the quasi-particle energy: 180 MeV
● In QRPA cut-off neutron states with v n  10
Choosing of the pairing interaction:
2
6
HFB
pnQRPA
The strength of the T=0 pairing is not well evaluated,
In N. Vinh Mau, arXiv 0711, 3173 (2007), f=1.36,
In our calculation f = 0.0, 0.5, 1, 1.5, 1.7
KITPC, Jun 14th, 2012
GT excitations in Sn isotopes
14
-1
GT strength (MeV )
12
112
10
114
Sn
116
Sn
Sn
8
6
4
2
0
16
5
10
15
20
25
30
0
f=0.0
f=0.5
f=1.0
f=1.5
f=1.7
118
Sn
-1
GT strength (MeV )
0
5
120
10
15
20
25
30
0
5
10
15
20
25
30
15
20
25
30
124
Sn
Sn
8
0
0
5
10
15
20
Ex (MeV)
25
30
0
5
10
15
20
Ex (MeV)
25
30
0
5
10
Ex (MeV)
T=0 pairing has almost no effect on the main peak energies.
KITPC, Jun 14th, 2012
GT excitations in Sb isotopes
18
exp
T21
T32
T43
T54
Te1
Te2
16
EGT MeV
14
GT peak energy in Sb isotopes
E
-Eexp
th
< 1.5 MeV
12
10
8
6
112
114
116
118
120
A
KITPC, Jun 14th, 2012
122
124
Conclusion and outlook
●
Main peak energy of GT and charge-exchange SD transitions
in closed shell nuclei can supply good constraint for tensor force;
●
In media heavy nuclei such as Sn isotopes, the T=0 pairing force
has negligible effects on the main GT peaks;
●
GT main peak of media heavy nuclei such as Sn isotopes can
also supply good constraint for the tensor force;
●
GT excitations in other isotopes and isotonics will be studied;
●
Other spin-isospin excitations and the relevant quantities will
be studied so as to find constraints for the tensor force.
KITPC, Jun 14th, 2012
collaborators
G. Colò, INFN ,
Italy
K. Miki, RCNP, Japan
H. Sagawa, Aizu univ. Japan
F. R. Xu,
PKU, China
H. Q. Zhang,
CIAE,
China
X. Z. Zhang,
CIAE,
China
KITPC, Jun 14th, 2012
KITPC, Jun 14th, 2012