Grupo de Física Nuclear Experimental G F E N CSIC I M E 15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CS IC 1 Hirschegg’06: Astrophysics and Nuclear Structure Low-Lying resonant states in 9 Be María José García Borge Århus-Göteborg-ISOLDE-Madrid-York Collaborations Outline: Motivation Asymmetries in A= 9 isobar Excited states in 9 Be accessible in the - decay of 9 Li Summary and Outlook E exc ( 9 Be) Q
Hirschegg’06: Astrophysics and Nuclear Structure. Low-Lying resonant states in 9 Be. María José García Borge Århus-Göteborg-ISOLDE-Madrid-York Collaborations. Outline: Motivation Asymmetries in A= 9 isobar Excited states in 9 Be accessible in the -decay of 9 Li Summary and Outlook. - PowerPoint PPT Presentation
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Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 1
Hirschegg’06: Astrophysics and Nuclear Structure
Low-Lying resonant states in 9Be
María José García Borge
Århus-Göteborg-ISOLDE-Madrid-York Collaborations
Outline:
Motivation
Asymmetries in A= 9 isobar
Excited states in 9Be accessible in the -decay of 9Li
Summary and Outlook
Eexc (9Be)Q
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 2
Why study -decay of Light Nuclei ?
“Exact” A-body calculations possible for A12
reaching lowest energy states for I ≤ 9/2
Green Funtion Monte-Carlo methodsNon-core Shell-model
Asymetries in mirror beta transitions
The (n,)9Be + 9Be(,n)12CCompetes with triple- in n-rich scenarios
Importance of the + n 5He(, )9Be
Experimentally -decay providesa clean way to feed unbound statesBreak-up mechanism not fixed by kinematics
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 3
Mirror asymmetry principle and Systematics
- : n → p + e- +
n p
ft-
+ : p → n + e+ +
E.C. : p + e- → n +
n p
ft+
Charge independence hypothesis of nuclear interactions symmetry of analog transitions
GTAFV BgBg
Kft
22
sg
KV
)6(61462 )3(587.12
2
V
A
gg
1
ft
ft
Isospin symmetry breaking asymmetry in mirror -decays
Thomas et al., AIP Conf. Proc 681, p. 235
Systematics of experimental values (A40)
= 4.8 (4) %
1
GT
GT
B
B
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 4
A = 9 Isobar
Nyman et al., NPA 510 (1990) 189 Mikolas et al., PRC 37 (1988) 766
F. Ajzenberg-Selove, NPA 490 (1988) 1
Large asymmetries 1
)(
)(
ft
ft
δ ≈ 3
δ=1.2±0.5
δ ≈ 0
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 5
ISOL method
point-like pure sources
-decay to populate state of interest
clean and selective
Use DSSSDs for complete kinematics
Large solid angle (rare events)
High Segmentation (avoid summing)
Effective Readout
Experimental technique for multiparticle detection
9Li
n
C-foil
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 6
9B high excited states
)2(for (9/8) MeV 0.3
)2/3(for (9/5) MeV 2
)0(for (9/8) keV 92
M
MM
8
5
8
firstrecoiling
firstrecoilingsum
Be
Li
Be
xEE
Ep,,(keV)
Esu
m
(MeV
)
IAS•Sequential Decay of 12.2 MeV State via 8Be(gs), 8Be(2+), 5Li(gs) and 5Li(1/2)
•R-Matrix-formalism applied.
•MC-simulations to account for efficiencies of each channel
•Results E: 12.19(4) MeV
: 450(20) keV
J: 5/2
BGT: 1.20(15)U.C. Bergmann et al., Nucl. Phys. A692 (2001) 427
Esu
m(M
eV
)
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 7
Spin Determination for states in 9Be
)1)(cos3(2
11)( 2
2 AW
Possible spins:
5/2 A2=-0.7143/2 A2=01/2 A2=1
Fit of the angular distribution breakup the 5He(3/2-) channelRev. Mod. Phys. 25 (1953) 729
n5He
9Li9Be3/2-
3/2-
?(-)
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 8
A = 9 Isobar
Nyman et al., NPA 510 (1990) 189Mikolas et al., PRC 37 (1988) 766
F. Ajzenberg-Selove, NPA 490 (1988) 1
δ ≈ 3
δ=1.2±0.5
δ ≈ 0
= 3.4(7)
= 0.032(3)
5/2-
5/2-
13.257
=0.45
54.1(15)%
NP A692(2001)427
PLB576 (2003)55
(1/2,5/2)-
(1/2)-
3/2-
3/2-
3/2-
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
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15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 9
5He 8Be(2+
)
Study of the 2.43 MeV, 5/2- state in 9Be
R-Matrix
form
alism
Tail through 5 He(gs)
E*= Esum + 1.57 MeV
Esum < 0.9 MeV
0 0.6
Hyper-spherical harmonics
Bochkarev , Sov J. Nucl. Phys. 52 (1990)
964
E (MeV)0 0.6
8Be(gs)
Fit
Data
Fit
Data
0.3
E (MeV)0.3
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 10
Study of low lying levels 9Be
8Be(g.s.)
5He 8Be(2+)
0.9 Esum 1.3 MeV
J = 1/2
2.78 MeV level
6 Esum 7 MeV
J = 5/2(e,e’p) Unpbl.
Tilley,NPA745(04)155
7.94 MeV Level
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 11
Contributions of the known -fed levels of 9Be
Sequential Decay
11.81 MeV State 8Be(gs), 8Be(2+), 5He(gs), 5He(1/2-), 8Be(4+)
7.94 MeV State 5He(gs), 8Be(gs)
2.78 MeV State 8Be(2+), 5He(gs)
2.48 MeV state (Bocharev et al., Sov. J. Nucl. Phys. 52(90)964)
R-Matrix-formalism applied.
MC-simulations to account for efficiencies of each channel
E, MeV
Missing Intensity
Incoherent sum of all channels
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 12
Is any other level of 9Be contributing?
3 Esum 4 MeV
J= 3/2
1.8 E1 + 0.7 Esum 1.8 E1 + 1.1
Elevel = 5.0(5) MeV, = 2.0(2) MeV
Grupo de Física Nuclear
Experimental
GFE
N
CSICI
ME
15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 13