Transcript Hadronic Physics Overview

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Nilsson Model 50 years
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Nuclear Experimental
Low-Lying resonant states in the 9Be continuum
María José García Borge
Århus-Göteborg-ISOLDE-Madrid-York Collaborations
Outline:
Motivation
Experimental Tools & Analysis Methods
Excited states in 9Be E < 9 MeV
Summary and Outlook
Lund, Sweden
14-18 june 2005
M.J.G. Borge IEM, CSIC
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FG
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Why study -decay of Light Nuclei ?
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Nuclear Experimental
“Exact” A-body calculations possible for A12
reaching lowest energy states for I ≤ 9/2
Green Funtion Monte-Carlo methods
Non-core Shell-model
The (n,)9Be + 9Be(,n)12C
Competes with triple- in
n-rich scenarios
Importance of the  +n5He(,  )9Be
Experimentally -decay provides
a clean way to feed unbound states
Break-up mechanism not fixed by kinematics
Lund, Sweden
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M.J.G. Borge IEM, CSIC
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Break-up to multi-particle final states
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Characteristics
 Kinematics not fixed
by conservation laws

The mechanism of
X->Y can be studied
sequential,
simultaneous,
democratic...

Need complete
kinematics measurement
to fully characterise
final state
Sequential
E,G
X
Direct
E,G

Connection to level
structure closer for
direct break-up.

Lund, Sweden
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X
E,G
X
Y
E1  G 1
?
Y
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A = 9 Isobar
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≈3
 = δ3.4(7)
5/2-
(3/2)-
5/2-
13.257
G=0.45
(1/2,7/2)-
(1/2)-
δ=1.2±0.5
54.1(15)%
(3/2)-
δ ≈= 00.032(3)
Nyman et al., NPA 510 (1990) 189
PLB576 (2003)55
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Mikolas et al., PRC 37 (1988) 766
F. Ajzenberg-Selove, NPA 490 (1988) 1
M.J.G. Borge IEM, CSIC
NP A692(2001)427
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Experimental technique for multiparticle detection
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Nuclear Experimental
9Li
ISOL method
 -decay to populate state of
interest
 clean and selective
n
Cfoil
 Use DSSSDs for complete
kinematics
 Large solid angle (rare events)
 High Segmentation (avoid
summing)
 Effective Readout
Lund, Sweden
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Analysis Method
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Nuclear Experimental
Precise determination of the source position
The radioactive beam is completely stopped in the thin carbon foil
 it decays at rest  linear momentum conservation
    

Pi  Pf  P1  P2  P3  ΔP
The uncertainties coming from the finite size of the pixel


ΔP  0, ΔPmaximum  20  30 MeV/c
Triple coincidences
Identification of particles
Removal of beta contamination
Lund, Sweden
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Double coincidences
Reconstruction of the third particle
M.J.G. Borge IEM, CSIC
P1+ P2+ P3=0 less precise
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Beta Filters
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n
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The beta particle taken as an alpha
 wrong reconstruction
 beta filters needed
•Anticoincidences with
the back detectors
•|Efront-Eback|<100 keV
n
n
•A cut in the total linear
momentum
ΔP<30 MeV/c
•E(deposited) > 200 keV
Lund, Sweden
14-18 june 2005
M.J.G. Borge IEM, CSIC
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Double coincidences in 9Li decay
Grupo de Física
Nuclear Experimental






P1  P 2  Pn  0  Pn  ( P1  P 2 )
9Li
E*(9Be) = Esum + 1.57 MeV (n breakup)
Ultra-thin entrance
window Detectors
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14-18 june 2005
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beam @ 20 keV
Tengblad et al.,
NIMA525 (2004)458
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Study of the 2.43 MeV state in 9Be
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Nuclear Experimental
9Li
beam 20 keV
40 g/cm2 C-foil
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E*= Esum + 1.57 MeV
Esum < 0.9 MeV
M.J.G. Borge IEM, CSIC
0
E (MeV)
0.6
0
E (MeV)
0.6
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Spin Determination for states in 9Be
Nuclear Experimental
Fit of the angular distribution
breakup  the 5He(3/2-) channel
Rev. Mod. Phys. 25 (1953) 729
1
W ( )  1  A2 (3 cos2 ( )  1)
2
9Li
Possible spins:
3/2-
9Be
?(-)
5/2  A2=-0.714
3/2  A2=0
1/2  A2=1
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

5He
3/2-
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
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Study of low lying levels 9Be
5He
8Be(2+)
7.94 MeV Level
8Be(g.s.)
6  Esum  7 MeV
J = 5/2
(p,p’) data
PRC43(91)1758
2.78 MeV level
0.9  Esum  1.3 MeV
J = 1/2
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Contributions of the known -fed levels of 9Be
Grupo de Física
Nuclear Experimental
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 
Missing
Intensity
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
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E, MeV
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Is any other level of 9Be contributing?
Grupo de Física
Nuclear Experimental
3  Esum  4 MeV
J= 3/2
1.8 E1 + 0.7  Esum  1.8 E1 + 1.1
Elevel = 5.0(5) MeV, G= 2.0(2) MeV
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Candidates in the literature?
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EElevel
MeV,G=
G=22MeV,
MeV,JJ==3/2
3/2- level==55MeV,
Shell Model
(p,p’) @ 180 MeV
5.09
βdecay
BGT
0.005
4.87
5.49
4.66
0.069
0.014
0.081
7.48
7.66
6.91
7.39
0.140
0.004
0.010
0.032
Spin E*(9Be)
(MeV)
3/2-
5/2-
Reference
Cohen-Kurath (6-16)BME
(1965)
Millener
Kumar (1974)
Cohen-Kurath (8-16) POT
(1965)
Cohen-Kurath (6-16)BME
Millener
Kumar (1974)
Cohen-Kurath (8-16) POT
(1965)
Elevel = 5.6(1) MeV, G= 1.33(36) MeV, J = 3/2Dixit et al., Phys. Rev. C 43(91)1758
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Fit alpha spectrum from 9Li decay
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Nuclear Experimental
Singles
New
Level
E*(9Be)
(MeV)
g.s.
2.43
2.78
5.0
7.94
11.81
Lund, Sweden
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Ip
3/25/21/23/25/25/2-
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G(keV)
0.77 ±0.15
1080±110
2000±500
~1000
400±30
B.R. (%)
Coinc
49.2±0.9
29.6 ±1.3
15.7±0.8
3.2±1.0
0.68±0.12
1.62±0.07
Singles
49.2±0.9
31.9 ±3.4
11.6±2.2
3.15±0.4
1.5±0.4
2.7±0.4
Langevin
50.5±5
34±4
10±2
Nyman
50±3
30±3
16±3
1.5±0.5
<2
2.7±0.2
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Summary & Outlook
Nuclear Experimental
Beta-delayed multi-particle emission is a powerful tool
If study in full kinematics
Decay mechanism
E, G, spin...
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 State
Firm assignment of J=7/2 for the 7.94 MeV
Confirmation of broad 3/2- state at 5 MeV, G= 2 MeV
Evidence of the contribution of decay via 5He(g.s.)
FUTURE:
Break up of the 2.34 MeV level in 9Be
11Li: Disentangle the breakup of the 18.1 MeV state in 11Be
Comparison of BGT distribution between 11Li and its core 9Li
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Collaborators
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Århus
University
C.Aa. Diget
H.O.U. Fynbo
H. Jeppesen
K. Riisager
University
Chalmers
Univ of
Technology
Inst. Estructura
de la Materia
B. Jonson
L.M. Fraile
M. Meister
Y. Prezado
G. Nyman
O. Tengblad
T. Nilsson
K. Wilhelmsen
of York
B.R. Fulton
Lund, Sweden
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Calculation of B(GT) for the 11.81 MeV level in 9Be
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-singles from 9Li decay Normalisation. n(4.5-5.5) = (30±3)
x10-4
Corrections:
0.335 of  in (4.5-5.5) MeV
Energy dependence of “f” (1.1)
Part of 11.81 Mev peak out of
the range (0.76)
BGT= 5.3 ± 0.9
BGT =5.6 ± 1.2 
Nyman et al., NPA 510 (1990) 189
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Comparison of 9Li & 9C decays
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•There is no asymmetry in the beta-decay of 9C
and 9Li to the ground states of 9Be and 9B.
•With respect to the mirror transitions to the
high energy region
Nuclear Experimental
9Be
Energy 11.81(0.15) MeV a
9B
12.19 (0.04) MeV
Width
400(30) keV a
450 (20) keV
Spin
5/2-
5/2-
Same spin and same width
a
F. Ajzenberg-Selove NPA 490 (1988) 1
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9B
FG
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excitation energy
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Nuclear Experimental
Esum 
M recoiling  M first
M recoiling
Efirst
  92 keV (9/8) for 8Be (0 )

 x  2 MeV (9/5) for 5Li (3 / 2 )
  3.0 MeV (9/8) for 8Be (2 )

Esum (MeV)
IAS Decay of 12.2 MeV
•Sequential
State  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
G: 450(20) keV
Ep,,(keV)
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J: 5/2
BGT: 1.20(15)
Bergmann et al., NPA692 (2001) 427
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Beta feeding to the 11-12 MeV region in 9Be
Grupo de Física
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Fit of the high energy peak gating on
the 5He(3/2-) channel
-emission 
5He(gs)-channel
11.81 MeV state  91±10%
11.28 MeV state  9 %
(e,p)-scattering on 9Be assumed J = 7/2
Only the participation of the
11.81 MeV state in 9Be
for the beta feeding is
considered
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Asymmetry in the A=9 isobars
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Sequential decay
 open channels
MC-Simulations
 Geometrical eff. & angular correlations
9C
 9B (12.19 MeV, 5/2) B(GT) = 1.20 (15) / 1.58(16) [PRC61(2000) 064310]
8Be(0+)
+p
0.090 (10)
0.085 (14)
9Li
8Be(2+)
+p
0.25 (7)
0.18 (3)
8Be(4+
)+p
-
5 He(3/2-)+
0.60 (7)
0.74 (8)
5 He(1/2-)
+
Ref
0.06 (4) This work, NPA 692(2001)427
PRC61(2000)
 9Be (11.8 MeV, 5/2) B(GT) = 5.3 (9)
8Be(0+)
+n
0.02(0.01)
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8Be(2+)
+n
0.11(0.06)
8Be(4+
)+n
0.12(0.08)
5 He(3/2-)+
5 He(1/2-)
0.28(0.06)
0.47(0.07)
M.J.G. Borge IEM, CSIC
+
This work
Y. Prezado, Phys. Lett B576 (2003) 55
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