Transcript Exotic Nuclei and Yukawa`s Forces

INPC
Tokyo
June 4-8, 2007
Exotic Nuclei
and
Yukawa’s Forces
Takaharu Otsuka
University of Tokyo / RIKEN / MSU
T. Suzuki
Nihon U.
R. Fujimoto Hitachi Ltd.
H. Grawe
GSI
Y. Akaishi KEK
P. Ring
TUM
D. Abe
T. Matsuo
M. Honma
Y. Utsuno
G. Lalazissis
Many experimentalists
Tokyo
Hitachi Ltd.
U. Aizu
JAEA
Thessaloniki
Outline
1. Introduction - Past and present issues 2. Shell structure and magic numbers of exotic nuclei
3. Deformation driven by tensor force
4. Relevant topics (neutrino, Lattice QCD, Superheavy)
5. Summary
Studies on exotic nuclei in 1990’s
Left-lower part of
the Nuclear Chart
proton halo
Stability line and drip lines
Proton number 
are not so far from each
other
 Physics of loosely bound
neutrons, e.g., halo
while other issues like
32Mg
neutron halo
11Li
リチウム１１
Neutron number 
neutron skin
A nuclei
(mass number)
stable
exotic
-- with halo
Neutron halo
Strong tunneling of loosely bound
excess neutrons
About same
radius
11Li
208Pb
Breakup of 11Li
Nakamura et al.,
Phys. Rev. Lett.
96, 252502 (2006)
F7-1 Nakamura
Proton number 
In the 21st century, a wide
frontier emerges between the
stability and drip lines.
Stability line
Drip line
What
happens
here ?
1990’s
neutron halo etc.
中性子数
Neutron
number 
（同位元素の種類）
A nuclei
(mass number)
stable
exotic
Riken’s work
Basic picture was
Island of Inversion
energy
deformed
2p2h state
intruder ground state
stable
Island of Inversion :
Ne, Na, Mg with N=20-22
Phys. Rev. C 41, 1147 (1990),
Warburton, Brown and Becker
exotic
pf shell
N=20
sd shell
gap ~
constant
The Key : Tensor Force
p meson : primary source
r meson (~ p+p) : minor (~1/4) cancellation
Ref: Osterfeld, Rev. Mod. Phys. 64, 491 (92)
p, r
Multiple pion exchanges
 strong effective central forces in NN interaction
(as represented by s meson, etc.)
 nuclear binding
This talk : First-order tensor-force effect
(at medium and long ranges)
One pion exchange  Tensor force
Intuitive picture of monopole effect of tensor force
wave function of relative motion
spin of nucleon
large relative momentum
attractive
small relative momentum
repulsive
j> = l + ½, j< = l – ½
TO et al., Phys. Rev. Lett. 95, 232502 (2005)
N=16 gap : Ozawa, et al., PRL 84 (2000) 5493;
Brown, Rev. Mex. Fis. 39 21 (1983)
d3/2
d5/2
Tensor
force
only
exchange
term
Example : Dripline of F isotopes is 6 units away from O isotopes
Sakurai et al., PLB 448 (1999) 180, …
Nuclei or regions
to be discussed
Island of
Inversion
51Sb 50Sn
36Kr
Neutrino
reaction
42Si
Superheavy
R process
78Ni
Chart provided by Sakurai
2. Shell structure and magic numbers
of exotic nuclei
51Sb
case
Opposite monopole
effect from
tensor force
with neutrons
in h11/2.
1h11/2 protons
1g7/2 protons
Z=51 isotopes
h11/2
g7/2
No mean field theory,
(Skyrme, Gogny, RMF)
explained this before.
Tensor by
p+ r meson
exchange
+ common effect
(Woods-Saxon)
1h11/2 neutrons
Exp. data from J.P. Schiffer et al., Phys. Rev. Lett. 92, 162501 (2004)
Hartree-Fock calculation including tensor force
Single-particle energies of exotic Ni isotopes
w/o tensor
with tensor
Gogny-type
(finite-range)
+
Tensor Force
N=28 Gap
Z=28 Gap
neutron g9/2
neutron g9/2
TO, Matsuo, Abe,
Phys. Rev. Lett. 97,
162501 (2006)
Contributions of Kinetic+Central, 2-body LS, and Tensor
components to the change of f7/2 – f5/2 gap
in going from N=40 to N=50 (g9/2 occupancy)
Kin+Cent and LS : almost the same among three calculations
Tensor : largest effect
TO, Matsuo, Abe, Phys. Rev. Lett. 97, 162501 (2006)
Hartree-Fock-Bogoliubov calculation including tensor force
Poster by Abe QW-048
Two neutron separation energy
D1S
Sn
no tensor
GT3
tensor
Kr
EXP
ng7/2
nh11/2
Heavy Sn
and Kr are
more bound
6
4
2g
2
7
6
5
4
3
2
1
f7/2-f5/2
p
d5/2-d3/2
p3/2-p1/2
p
1g
1h
f7/2-f5/2
Crucial for
42Si
mentioned later
M. Zalewski, W. Satuła, J. Dobaczewski,
(preliminary)
1i
An example by Dobaczewski et al.
d5/2-d3/2
Zero-range
version of tensor force
p3/2-p1/2
(Skyrme 1956, Stancu et al. 1977)
SkP original
SkP T Tensor + SO*0.8
Spin-orbit splittings [MeV]
SkP
1g 1h
n
8Skyrme
+ Tensor’SkP
: TManynrecent works
October, 2006
Dec. 22, 2006
February, 2007
F10-2
April, 2007
Relativistic Mean Field
Exchange terms
Proton
1h11/2 – 1g7/2 gap
Relativistic Hartree-Fock
Lalazissis et al.
NL3 is used
Full tensor
Half tensor
No tensor
Long et al.,
Toki et al., …
3. Deformation driven by Tensor-force
Recent finding about the shell-model interaction
Effective shell-model interaction (refined empirically)
= central part
+ tensor
p + r meson exchange
~
(for medium- and long-range parts)
+ …
This feature is true also in G-matrix
A new shell-model interaction has been constructed
for the sd + pf shells.
Chiral Perturbation of QCD
Short range central forces
have complicated origins and
should be adjusted.
S. Weinberg, PLB 251, 288 (1990)
Tensor force is explicit
Tensor force can drive nuclei to (or from) deformation
f7/2
d3/2
Si isotopes
Exp.
neutron
s1/2
d5/2
proton
Strong oblate
full
Deformation
?
Potential Energy Surface
42 Si
14 28
Tensor force removed
from cross-shell interaction
Z=28 gap is reduced also by tensor force
Debate over
42Si
Nature 435 (2005), MSU
44S
->
42Si
cross section small
deformed
PRL accepted (2007), GANIL
42Si
oblate
44S
prolate
Cauier et al. Shell Model, Werner et al. Skyrme model,
Lalazissis et al. RMF, Peru et al. Gogny model,
Rodriguez-Guzman et al. Gogny model
Modification to the Island of Inversion
Terry et al, PLB 640 (2006) 86
Low-lying 3/2- level
(0.765 MeV) in 27Ne
 N=20 gap smaller
N=20 gap changes
~6MeV
~3MeV
O Ne Mg
Ca
Expansion
of the
territory
Neyens et al. Mg
Tripathi et al. Na
Dombradi et al. Ne
3. Intriguing relevant topics
Relevance to Weak Processes
Neutrino reaction cross section is enlarged
by using interaction containing full tensor force
Over Woosley
Over PSDMK2
Presented by
Suzuki H4-2
Temperaturte of supernovae explosion
Tensor effective forces are close to bare ones.
accepted by PRL
sstt central force
calculated by
a Lattice QCD
calculation
Presented by
Ishii D1-4
Calculations for tensor and 3-body forces will be great
Modification of superheavy magic gap
by tensor force
Occupations of 1k17/2
and 2h11/2 reduces
Z=114 gap to a half value
Energy (MeV)
3p1/2
3p3/2
1k17/2
2f5/2
2h11/2
Z=114
2f7/2
1i13/2
N=184
1h9/2
Proton
Proton single-particle energies
by Woods-Saxon potential (A=300)
Neutron
Story similar to
Z=64 subshell closure
Summary
There are typically 20~100 isotopes between the
stability and drip lines. They may give us a rich
field of “harvest” from the NN interaction.
By changing N (Z) so much, unknown or unrecognized
aspects of the NN interaction may emerge.
This was the motivation of the project of the tensor
force.
The outcome so far are …
Summary - 2
- Shell evolution due to tensor force
- is a robust mechanism -- also for many classical cases --
- occurs from p-shell to superheavies
developments in pf shell ex. N=34 new magic
ANL, MSU, GANIL, REX-ISOLDE
- affects deformation (ex. Doubly-magic 42Si  strongly oblate)
- Free tensor force (like p+r)  many-body structure
more input from ChP., eff. field th., lattice QCD
- Other cases …
Weak processes, astrophysical implications, ….
11Li and tensor force Myo F3-3
Thanks to Yukawa,
mesons create
variety and richness
of exotic nuclei.