1. g-ray spectroscopy of the sd-shell hypernuclei
Graduate school of Science, Tohoku University
T. Koike
Hyperball-J collaboration
Survey of sd-shell hypernuclear cores
g-ray spectroscopy of well deformed hypernuclei
25LMg
Summary

2. Z=20
39Ca
40Ca
Possible sd-shell L hypernuclei via g-ray spectroscopy with (K-,p-) & (p+,K+) reactions
38K
39K
38Ar
39Ar
40Ar
34Cl
35Cl
37Cl
36Cl
39Cl
31S
32S
34S
36S Z
30P
31P
27Si
28Si
30Si
26Al
27Al
Most abundant isotopes (target)
23Mg
24Mg
25Mg
26Mg
~10% abundance
22Na
23Na
24Na
25Na
proton decay
19Ne
20Ne
21Ne
22Ne
neutron decay
18F
19F
E13
21F N
Z=9

3. Bound states of sd-shell nuclei and hypernuclei
Co-existence of shell (mean field) and cluster-like structures
More valence nucleons
higher level densities (especially odd-odd)
Collective (rotational) excitation spectrum → low-lying energy
pL states also bound
Shell model
Cluster model
Self-consistent calculations (12/4 Hagino)
RMF
Hatree-Fcok+BCS
AMD (12/4 Kimura)
D. J. Millener et al.,
Phys. Rev. C, (1988)

4. Bn Bp
Ex(pL)
Target A -1ZXn-1

5. (mostly via non-mesonic in the sd-shell hypernuclei)
28LSi sL pL dL
SKSMinus?
(p+,K+) T.Hasegawa et al., Phys. Rev. C 53, 1210 (1996)
g-g coincidence
with Hyperball-J
A-1LZ g
A-1LZ-1 g g
ALZ
Weak decay
(mostly via non-mesonic in the sd-shell hypernuclei)

6. Z=20
39Ca
40Ca
Possible sd-shell L hypernuclei via g-ray spectroscopy with (K-,p-) & (p+,K+) reactions
38K
39K
38Ar
39Ar
40Ar
34Cl
35Cl
37Cl
36Cl
39Cl
even-even
mirror
31S
32S
34S
36S Z
30P
31P
27Si
28Si
30Si
26Al
27Al
Most abundant isotopes (target)
23Mg
24Mg
25Mg
26Mg
~10% abundance
22Na
23Na
24Na
25Na
proton decay
19Ne
20Ne
21Ne
22Ne
neutron decay
18F
19F
E13
21F N
Z=9

7. g b (b, g=60°) (b, g=0°) Non collective oblate triaxial spherical
prolate
(0,0)
(b, g=0°)

8. Skyrme Hartree-Fock +BCS
Myaing Thi Win et al., submitted to PRC
self-consistent mean field
Skyrme-type LN interaction
PES of L hypernuclei with triaxial deformation: E(b,g)
Angular momentum not good quantum number
24Mg, 24Mg+L +L

9. Spectra of a deformed even-even nucleus (collective excitation mode)
g-band
22+
31+
42+
E(41+)/E(21+)
b-band
02+
23+
43+
41+ g
21+
vibrational
v.s.
rotational 0+
K=0, nb=1, ng=0
b2, J
K=2, nb=0, ng=1
K=0, nb=0, ng=0

10. 21+, 22+, and 02+
26Si
38Ar
38Ca
18(▲) ,20Ne
22(▲) ,24Mg
30S

11. Rotational v.s. Vibrational
22Mg
24Mg
26Si
38Ar
18Ne
Rotational
Vibrational
38Ca
20Ne

12. g-ray spectroscopy of 25LMg
Well deformed & even-even core hypernuclei
low and simple (regular) energy level
direct observation of core polarization effect of L
Nuclear density saturation at the g.s. with little change in size, but a shape can change in (b,g) plane
A few 100 keV change
Observation of spin averaged 21+, 22+, 02+→（b,g）
Observation of 41+
pL -bound-states particle stable (Bp=11693keV Bn=16532 keV)
Observation of pL splitting in the sd-shell
Hyperball-J with LaBr, CsI detectors (?)
Use of a natural target
possibility of increasing the number of accessible hypernuclei
a test case for heavier hypernucley beyond sd-shell

13. 24Mg level scheme pL pL pL
T=0
T=0
12C
13LC
24Mg
25LMg

14. Use of a natural Mg target sL pL dL 24Mg (0+) 0.79 L 24LMg 23LNa 23LMg
core
23Mg
22Na
22Mg
25Mg
(5/2+)
0.10
25LMg
24LMg 24
26Mg
0.11
26LMg
25LNa
24Na
even-even
odd-A
odd-odd

15. Mg even-even core: 22,24Mg
T=0
T=0
2212Mg10(2)
2412Mg12(4)

16. Use of natural Mg target and identification of six L hypernuclei
sL, dL
sL , pL sL dL
23LNa
26LMg
24LNa
10%
11%
79%
25LMg
24LMg
23LMg
27Al(K-,p-)
→ p+26LMg (pL gate)
←dL
23Na(K-,p-)→23LNa (sL gate)

17. Summary The sd-shell region more vast than the p-shell
Importance of coupling of L to nuclear collectivity (non-spherical vacuum) in the sd-shell
Core polarization effect of L in the 2D (b,g) plane
Measurement of the inter shell (pL→sL) g ray
g-ray spectroscopy of 25LMg with a use of natural target (Hyperball-J, SKSMinus, LaBr3/CsI detectors?)
Essential role of g-g coincidence technique in the sd-shell