Tomás Borge: Carlos, el amanecer ya no es una tentación / Carlos, now the Dawn's no Fond Illusion
Grupo de Física Nuclear Experimental G F E N CSIC I M E 15-21 January 2006, Hirschegg,...
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Transcript of Grupo de Física Nuclear Experimental G F E N CSIC I M E 15-21 January 2006, Hirschegg,...
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
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CSICI
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 13
Candidates in the literature?
Elevel = 5 MeV, = 2 MeV, J = 3/2-Elevel = 5 MeV, = 2 MeV, J = 3/2-
Elevel = 5.6(1) MeV, = 1.33(36) MeV, J = 3/2-
Dixit et al., Phys. Rev. C 43(91)1758
(p,p’) @ 180 MeV Shell Model
Spin E*(9Be) (MeV)
β-decay BGT
Reference
3/2- 5.09 0.005 Cohen-Kurath (6-16)BME (1965)
4.87 0.069 Millener 5.49 0.014 Kumar (1974) 4.66 0.081 Cohen-Kurath (8-16) POT
(1965) 5/2- 7.48 0.140 Cohen-Kurath (6-16)BME
7.66 0.004 Millener 6.91 0.010 Kumar (1974) 7.39 0.032 Cohen-Kurath (8-16) POT
(1965)
Mikolas et al., PRC 37 (1988) 766
Grupo de Física Nuclear
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GFE
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15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 14
Fit alpha spectrum from 9Li decay
New
Level
Singles
E*(9Be) (MeV)
Ip (keV) B.R. (%)
Coinc Singles Langevin Nymang.s. 3/2- 49.2±0.9 49.2±0.9 50.5±5 50±32.43 5/2- 0.77 ±0.15 29.6 ±1.3 31.9 ±3.4 34±4 30±32.78 1/2- 1080±110 15.7±0.8 11.6±2.2 10±2 16±35.0 3/2- 2000±500 3.2±1.0 3.15±0.4
7.94 5/2- ~1000 0.68±0.12 1.5±0.4 1.5±0.5 <211.81 5/2- 400±30 1.62±0.07 2.7±0.4 2.7±0.2
Langevin et al.,Nucl. Phys. A366 (1981) 449
Nyman et al., Nucl. Phys. A510 (1990) 189
Grupo de Física Nuclear
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15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 15
Summary & Outlook
The low lying resonance states in 9Be have been investigated via -delayed particle emission from 9Li.
Angular correlations used for firm spin determination First exp. determination of the J=1/2 character of 2.78 MeV
StateFirm assignment of J=5/2 for the 7.94 MeV
Confirmation of broad 3/2- state at 5 MeV, = 2 MeVEvidence of the contribution of decay via 5He(g.s.)
FUTURE: Break up of the 2.43 MeV level in 9Be11Li: Disentangle the breakup of the 18.1 MeV state in 11Be
Comparison of BGT distribution between 11Li and its core 9Li
The beta-decay asymmetry in the A= 9 isobar system studied for the gs and high excited ( 12 MeV) states in 9Be & 9B
12MeV Sequential breakups for p and n Confirmed large asymmetry = 3.4 (1.0)
Beta asymmetry to the g.s. negligible must be due to differences in the structure of the two final state resonances
Grupo de Física Nuclear
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15-21 January 2006, Hirschegg, Austria M.J.G. Borge, IEM CSIC 16
Collaborators
Århus University
C.Aa. Diget
H.O.U. Fynbo
H. Jeppesen
K. Riisager
U. Bergmann
Chalmers Univ of Technology
B. Jonson
M. Meister
G. Nyman
T. Nilsson
K. Wilhelmsen
Inst. Estructura de la Materia
L.M. Fraile
Y. Prezado
O. Tengblad
University
of York
B.R. Fulton