Nuclear break-up of exotic nuclei

1
Nuclear break-up of exotic nuclei
I History of the towing mode in stable
nuclei the 40Ar58Ni _at_ 40 MeV/A case II The TDSE
calculation III The case of the 11Be break-up
IV The extension to borromean nuclei V
Conclusions - Perspectives
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2
Inelastic Channel-projectileejectile
A
A
A
A
A
Target
A1
Projectile
A
A
A
A
Inelastic Scattering GR and multiphonons
Knock Out
Pick-up Break-up
New mechanism?
1 emitted particle
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1 or several emitted particle(s)
3
Angular distribution of nucleon emitted in
58Ni(40Ar, 40Ar n or p)
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Action
t
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5
What happens when a force acts on a mass
for a given period of time ?
Action
d ? (ro . A1/3) 4 fm
d
E 40 MeV/A
tc
vp
vp 1023 fm.s-1
.
.
F
x . tc xo
tc 4. 10-23 s
m
F 15 MeV.fm-1
3 fm
15 . 9 . 1046
.4. 10-23 6.1022 fm.s-1
900
Right order of magnitude!
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6
Nuclear break-up of exotic nuclei
I History of the towing mode in stable nuclei
the 40Ar58Ni _at_ 40 MeV/A case II The TDSE
calculation III The case of the 11Be break-up
IV The extension to borromean nuclei V
Conclusions - Perspectives
Jass
7
Evolution of a one-particle wave function via
the resolution of time dependent Schrödinger
J.A. S. D. Lacroix Ph. Chomaz

Static solutions
H



(
r
)
H ? ? . ????? diagonalization ???eigen
states, eigen values
Exact up to 2sd order
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D.Lacroix et al. Nucl. Phys. A658 (1999) p273
8
Resolution of time dependent Schrödinger
equation on a mesh non perturbative calculation

• The calculation includes
• TDSE for a wave function in a moving potential
• diffraction (refraction!) through the nuclear
  potential
• single particle excitations to unbound states
• n-core excitations (!!)
•  shaking   of the core (Coulomb classical
  trajectory)

proj
target
proj

• The calculation does not include
• spin-orbit, pairing
• No structure info
• core or target excitations (not excluded either)
• nucleon-nucleon dissipation
• quantum relative motion
• energy conservation

target
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Evolution of a wave function via the resolution
of time dependent Schrödinger
t 0
t 130 fm/c
Initial wave function
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10
y
Initial Density Probability in the target
potential at rest in the lab frame.
Evolution
x
Density probablility after the projectile has
passed
FFT
py
ds/dW (q)
Fourier transform of the former density
probability.
px
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Angular distribution of the emitted particle
11
58Ni(40Ar,40Arp or n)
2p calculation, b from 10 to 12 fm Plus flat
background
50
py
50
2s
px
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12
Nuclear break-up of exotic nuclei
I History of the towing mode in stable nuclei
the 40Ar58Ni _at_ 40 MeV/A case II The TDSE
calculation III The case of the 11Be break-up
IV The extension to borromean nuclei V
Conclusions - Perspectives
Jass
13
11Be break-up calculations
WS potential to bound the 2s by 0.5 MeV
Density of 2s
2000
13 fm
Does not change when using N.Vinh Mau potential
80
15
1
Need to use a Coulomb trajectory
Weakly bound neutron
Large Coulomb break up
Runge Kutta r(tdt) r(t-dt)
2.dt.p(t)/m p(t) p(t-2dt) 2.dt.F(t-dt)/m
Imaginary time evolution extract a
stable eigen state (M.Fallot...) for the
cartesian mesh
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Interpolation ...
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Neutron angular distributions Au,Ti,Be (11Be,
10Be n) _at_ 41 Mev/A Data from R.Anne et
al.,Nucl.Phys. A575 (1994) 125
lab
lab
lab
neutron
neutron
neutron
M.Fallot, J.A.Scarpaci, D.Lacroix, Ph. Chomaz et
J.Margueron, Nuclear Physics A700 (2002) 70
Large b (Coulomb break-up) forward peaked
emitted neutron Small b (nuclear break-up)
responsible for neutrons emitted at large angle
The nuclear break-up is fully reproduced by the
interaction of the particle with the mean field
of the target - no need of n-n interaction.
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11Be a halo nucleus
n

• Neutron bound by 0.504 MeV
• GS (Jp 1/2)
• GSgt a 2s1/2 ? 0gt b 1d5/2 ? 2gt

10Be
a2 (S2s) et b2 (S1d) spectroscopic factors
10Be 2 state of b20.74 Ref Auton et al. NP A
322(1970) 305
g
Eg3.37 MeV
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GANIL
SISSI

• Primary beam of 13C _at_ 75 A.MeV
• Secondary beam of 80000 11Be/s _at_ 41 A.MeV.

SPEG
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Experimental set-up
Experimental set-up results
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Experimental set-up results
TDSE Calculation
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The G.S. of 11Be
GSgt a 2s1/2 ? 0gt b 1d5/2 ? 2gt
S2s 85-36 S1d ?
Transfer reaction p(11Be,10Be)d GANIL
Fortier et al., PL B 461(1999)22-27
Break-up reactions (11Be,10Be) _at_ 60 MeV/u and
eikonal models
T. Aumann et al., P.R.L.84 (2000) 35-38
Break-up reactions (11Be,10Be) _at_ 520 MeV/u Palit
et al., PR. C 68, 034318 (2003)
nucl.
DWBA excitation and break-up
Large diversity of S2s
elect.
B.Zwieglinski et al. Nucl.Phys.A315, 124
(1979) N.K.Timofeyuk et al. P.R.C59, 1545 (1999)
Our work
20
Nuclear break-up of exotic nuclei
I History of the towing mode in stable nuclei
the 40Ar58Ni _at_ 40 MeV/A case II The TDSE
calculation III The case of the 11Be break-up
IV The extension to borromean nuclei V
Conclusions - Perspectives
Jass
21
Study of neutron correlationswith nuclear
break-up

• 6He is an archetype of a Borromean nucleus high
  intensities most suitable
  nucleus to investigate new experimental approach
  and develop new theoretical tools

Di-neutron configuration
Cigar configuration
Zhukov et al., Phys. Rep. 231 (1993) 151
three-body description expansions on
hyperspherical harmonics coordinate space
Faddeev approach
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22
Some experiments on 6He

• Transfer reactions 4He( 6He,6He) 4He
• dominated by di-neutron conf
• Yu.Oganessian et al. (1999) Dao T.Khoa and
  W.von Oertzen (2004)
• Radiative capture 6He(p,?)x _at_ 40 MeV/A - no ?
  t decay
• large distance between the two neutrons (cigar
  like)
• E.Sauvan et al. (2001)
• Coulomb break-up6He C, Pb _at_ 30-60 MeV/A
• large distance between the two neutrons (cigar
  like)
• Invariant mass ? interferometry depending on
  impact parameter cuts
• G.Normand et al. (2004) rn-n 7.7 fm, 9.4 fm
• F.M.Marques et al. (2000) rn-n 5.9 fm
• _at_ 240 MeV/A 6,8He
  Pb _at_ 700 MeV/A
• L.V.Chulkov et al. (2005) QFS
  dominates
• low lying 1- states 3-6 MeV ? core plus 2 or 4
  neutrons
• 8He small 6He 2n

No consensus on the n-n configuration Open to
more experiments
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Neutron angular emission
extension of TDHF (TDDM) (M.Assie-D.Lacroix)
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G.Normand, PhD thesis 2004 F.M.Marques, PR C64,
2001
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Set-up
High neutron angular coverage up to 90 neutron
wall 20 additional detectors Si detector for
4He covering from 5 to 15
Additional neutron detectors
n
Faraday cup
4He
6He 20 MeV/u
5 mg/cm2 Pb target
Si det.
n
65
Neutron wall
25
Nuclear break-up of exotic nuclei
I History of the towing mode in stable nuclei
the 40Ar58Ni _at_ 40 MeV/A case II The TDSE
calculation III The case of the 11Be break-up
IV The extension to borromean nuclei V
Conclusions - Perspectives

• Reaction mechanism plays an important role in
  the break-up
• towing Mode, a spectroscopic tool
• need of good theoretical description to infer
  spectroscopic factors
• Development required for two-particle wave
  function evolution
• extension of TDHF - Marlène Assié, Denis Lacroix
• Possible application to cluster studies!
• observation of ? emission in 40Ca break-up

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