Post on 17-Jan-2016
description
transcript
-ray spectroscopy of the -ray spectroscopy of the sdsd-shell hypernuclei-shell hypernuclei
Graduate school of Science, Tohoku University
T. Koike
Hyperball-J collaboration
• Survey of sd-shell hypernuclear cores• -ray spectroscopy of well deformed hypernuclei
• 25Mg • Summary
1919FF
2020NeNe
2323NaNa
2424MgMg
2727AlAl
2828SiSi
3131PP
3232SS
3535ClCl
4040ArAr
3939KK
4040CaCa
3737ClCl
2626MgMg2525MgMg
2222NeNe
3030SiSi
3434SS
3939ClCl
3838ArAr
2323MgMg
2222NaNa
2727SiSi
2626AlAl
3030PP
3131SS
3434ClCl
3838KK
3939CaCaPossible sd-shell hypernuclei via -ray spectroscopy with
(K-,-) & (+,K+) reactions
Z
Z=20
Z=9
Most abundant isotopes (target)
abundance
proton decay
neutron decay
N
1919NeNe
1818FF
3939ArAr
3636ClCl
3636SS
2525NaNa2424NaNa
2121FF
2121NeNe
E13
Bound states of Bound states of sdsd-shell nuclei and hypernuclei-shell nuclei and hypernuclei
D. J. Millener et al., Phys. Rev. C, 38 2700 (1988)
• 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 •pstates also bound
• Shell model • Cluster model • Self-consistent calculations (12/4 Hagino)(12/4 Hagino)
•RMF•Hatree-Fcok+BCS
•AMD (12/4 Kimura)(12/4 Kimura)
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
18F
19Ne
22Na
23M
g
24M
g
25M
g
26Al
27Si
30P
32S
34C
l
39Ar
38K
39C
a
(keV
)SnSpEx(plambda)
BnBnBpBpEx(pEx(p
Target A -1ZXn-1
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
18F
19Ne
23M
g
24M
g
25M
g
26Al
27Si
30P
32S
34C
l
39Ar
38K
39C
a
(keV
)
28Si
s
pd
(+,K+) T.Hasegawa et al., Phys. Rev. C 53, 1210 (1996)
AZA-1
Z-1 A-1Z
Weak decay
(mostly via non-mesonic in the sd-shell hypernuclei)
- coincidence with Hyperball-J
SKSMinus?
1919FF
2020NeNe
2323NaNa
2424MgMg
2727AlAl
2828SiSi
3131PP
3232SS
3535ClCl
4040ArAr
3939KK
4040CaCa
3737ClCl
2626MgMg2525MgMg
2222NeNe
3030SiSi
3434SS
3939ClCl
3838ArAr
2323MgMg
2222NaNa
2727SiSi
2626AlAl
3030PP
3131SS
3434ClCl
3838KK
3939CaCaPossible sd-shell hypernuclei via -ray spectroscopy with
(K-,-) & (+,K+) reactions
Z
Z=20
Z=9
Most abundant isotopes (target)
abundance
proton decay
neutron decay
N
1919NeNe
1818FF
3939ArAr
3636ClCl
3636SS
2525NaNa2424NaNa
2121FF
2121NeNe
even-even
mirror
E13
)2cossinsin3)1cos3((cos
16
51),( 22
0
RR
CollectiveCollectiveprolateprolate
(, =0°)
(0,0)
sphericalspherical
triaxialtriaxial
Non collective Non collective oblateoblate
(, =60°)
Skyrme Hartree-Fock +BCSSkyrme Hartree-Fock +BCS
• self-consistent mean field• Skyrme-type N interaction• PES of hypernuclei with triaxial deformation: E(E(,,)) • Angular momentum not good quantum number
Myaing Thi Win et al., submitted to PRC
24Mg, 24Mg+
0+
21+
41+
Spectra of a deformed Spectra of a deformed even-eveneven-even nucleus nucleus (collective excitation mode) (collective excitation mode)
E(41+)/E(21
+)
-band
02+
23+
43+
2, J
band
22+
31+
42+
vibrational
v.s.rotational
K=0, n=1, n=0
K=2, n=0, n=1
K=0, n=0, n=0
0
2
4
6
8
8 10 12 14 16 18 20Z
Exci
tatio
n en
rgy
(MeV
)
1st 2+2nd 2+2nd 0+
2211++, 2, 222
++, and 0, and 022++
26Si38Ar 38Ca
18(▲) ,20Ne 22(▲) ,24Mg
30S
Rotational v.s. VibrationalRotational v.s. Vibrational
E(4)/ E(2)
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
3.2
3.4
8 10 12 14 16 18 20 22Z
E(4)
/E(2
)
22Mg
24Mg
26Si 38Ar
18Ne
Rotational
Vibrational
38Ca20Ne
-ray spectroscopy of -ray spectroscopy of 2525MgMg
• Well deformed & even-even core hypernuclei– low and simple (regular) energy level– direct observation of core polarization effect of
• Nuclear density saturation at the g.s. with little change in size, but a shape can change in (,) plane
• A few 100 keV change• Observation of spin averaged 21
+, 22+, 02
+→ ( , )• Observation of 41
+
• p -bound-states particle stable (Bp=11693keV Bn=16532 keV)
– Observation of p 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
2424Mg level schemeMg level scheme
12C 13C 24Mg 25
Mg
pp
p
T=0 T=0
s p d
24Mg
(0+)
0.790.79 24Mg 23
Na 23Mg
core 23Mg 22Na 22Mg
25Mg
(5/2+)
0.10 25Mg 25
Mg 24Mg 24
core 24Mg 24Mg 23Mg26Mg
(0+)
0.11 26Mg 25
Mg 25Na
core 25Mg 24Mg 24Na
Use of a natural Mg targetUse of a natural Mg target
even-even odd-A odd-odd
22221212MgMg10(2)10(2)
24241212MgMg12(4)12(4)
T=0 T=0
Mg even-even core: Mg even-even core: 22,2422,24MgMg
Use of natural Mg target and Use of natural Mg target and identification of six identification of six hypernuclei hypernuclei
s, d
←d
27Al(K-,-)→ p+26
Mg (p gate)
23Na(K-,-)→23Na (s gate)
(1) Natural Mg (2) 27Al(3) 23Na
s,p
2323NaNa
2626MgMg
2424NaNa
10%10% 11%11%79%79%
2525MgMg2424
MgMg2323MgMg
s d
SummarySummary
• The sd-shell region more vast than the p-shell
• Importance of coupling of to nuclear collectivity (non-spherical vacuum) in the sd-shell – Core polarization effect of in the 2D (,) plane
• Measurement of the inter shell (p→s) ray
• -ray spectroscopy of 25Mg with a use of natural
target (Hyperball-J, SKSMinus, LaBr3/CsI detectors?)
• Essential role of coincidence technique in the sd-shell