Probing Light Neutron-Rich Systems

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Probing Light Neutron-Rich Systems
Nigel Orr Group Exotiques LPC-Caen for the
DEMON-CHARISSA Collaboration

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toujours la même chose avec lui mieux vaut
peut-être rester ici avec mon ballon de rouge

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Probing Light Neutron-Rich Systems

1. Motivation
2. Breakdown in the N8 shell closure - 12Be
3. Structure beyond the driplines
4. Spectroscopy of 13Be
5. N4 5H, 4n
6. Conclusions Perspectives ...

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Structure of light, very neutron-rich systems ...
10Li
9He
AZ corexn? correlations/clustering
4n
driplines and beyond experimentally
accessibleab initio calculations tractable,
Shell Model in Continuum, ...


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N8 shell closure - 12Be ?
1d5/22
n-threshold
p
n
0.32
1/2--
?
0
1p3/2
1/2
11Be
1s1/2
psd-shell ordering in 12Be?


Figure courtesy Jeff Tostevin, UNiS
nb first proposed by Fred Barker J. Phys.
G (1976)
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High-Energy, Single-Nucleon Removal

• s-1n 10-100mb, rs 100 mg/cm2
• forward focussing

g
ds/dp
T1N
g ? Excore ds/dp ? ?n s-1n(Jpcore) ?
C2S

REVIEW Hansen, Tostevin, Ann. Rev. Nucl. Part.
Sci. (2003)
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N8 shell closure C( 12Be,11Beg) _at_ 78
MeV/nucleon
sexpt vs sGlauber ?
?0
C2S (ns1/2) ? 0.5
C2S (np1/2) ? 0.4
Eg320 keV
?1
C2S (nd5/2) ?? n(p1/2)2,(s1/2)2,(d5/2)2 ?
30, 20, 50

A. Navin et al., PRL (2000)
G. Gori et al., PRC (2004)
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N8 shell closure - 12Be n(d5/2)2 admixture
1d5/22
n-threshold
p
n
0.32
10Ben
1/2--
?
0
1p3/2
1/2
11Be
1s1/2
psd-shell ordering in 12Be?

Figure courtesy Jeff Tostevin, UNiS

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Single-Nucleon Removal to Unbound
States/NucleiComplete Kinematics
vn
v0
v0
vcore
T1N
Target
pcoren pcore
pn Erel m(vcore- vn)2/2 qcore-n

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Experimental Setup Complete Kinematics
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Experimental Response Function Complex geometry
? simulations
FWHM 0.3 Ed 1/2
en
enn
CHARISSADEMON _at_ 30-40 MeV/nucleon

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Benchmark System - 7He
Er0.44, G00.16 MeV (g.s.)
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N8 shell closure C( 12Be,10Ben) _at_ 41
MeV/nucleon
Counts
5/2
3/2-
5/2-
Ex (11Be) MeV
LPC-CHARISSA-DEMON S. Pain, W.N. Catford, N.A.
Orr et al.
Ex (11Be) Erel(10Ben) Sn

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N8 shell closure C( 12Be,10Ben) _at_ 41
MeV/nucleon
Counts
s(5/2) 235 mb
? C2S (nd5/2) ? 0.4
5/2
3/2-
5/2-
Ex (11Be) MeV
LPC-CHARISSA-DEMON S. Pain, W.N. Catford, N.A.
Orr et al.

J.A. Tostevin Preliminary
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Core-n correlations modelling two-neutron halo
systems
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Core-n correlations modelling two-neutron halo
systems
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Core-n correlations modelling two-neutron halo
systems
14Be ? 12Be-n interaction ? spectroscopy of 13Be
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Single-Proton Removal C(14B,12Ben) _at_ 41
MeV/nucleon

• projectile neutron configuration preserved

? Final states populated ns1/2 and nd5/2
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C(14B,12Ben) _at_ 41 MeV/nucleon
Ed (MeV)
LPC Group Exotiques - JL Lecouey et al.
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C(14B,12Ben) _at_ 41 MeV/nucleon
s-wave resonance Er ? 0.7 MeV G0 ? 2 MeV
Ed (MeV)
LPC Group Exotiques - JL Lecouey et al.
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C(14B,12Ben) _at_ 41 MeV/nucleon
s-wave resonance Er ? 0.7 MeV G0 ? 2 MeV
d-wave resonance Er 2.5 MeV G0 0.4 MeV
Ed (MeV)
LPC Group Exotiques - JL Lecouey et al.
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Angular Correlations C(14Be,12Ben) _at_ 287 MeV/u

14Be
n1
13Be
n2
12Be

H. Simon et al., priv. comm.
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13Be Experiment-Theory
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13Be Experiment-Theory
13Be Ex 2.5 MeV nd5/2
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13Be Experiment-Theory
13Be ground state ns1/2 resonance (?)
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13Be Experiment-Theory
13Be np1/2 Ex ??
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5H correlations beyond the dripline

1. most neutron-rich system known - N/Z4
2. extreme test of models
3. n-n correlations beyond the dripline
4. contradictory observations ...

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5H correlations beyond the dripline

1. most neutron-rich system known - N/Z4
2. extreme test of models
3. n-n correlations beyond the dripline
4. contradictory observations ...

p(6He,pp) _at_ 36 MeV/uKorsheninnikov et al., PRL
(2000)
t(t,ptn) _at_ 19 MeV/uGolovkov et al., PLB (2004)
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Correlations beyond the dripline 5H
C(6He,tnn)X _at_ 30 MeV/nucleon

Group Exotiques - G. Normand et al.
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Correlations beyond the dripline 5H
C(6He,tnn)X _at_ 30 MeV/nucleon
Uncorrelated tnn/no FSI
(event mixing)

Group Exotiques - G. Normand et al.
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Correlations beyond the dripline 5H
C(6He,tnn)X _at_ 30 MeV/nucleon
Er1.8 0.2 MeV G02.1 0.5 MeV
Uncorrelated tnn/no FSI

Group Exotiques - G. Normand et al.
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Single-proton Removal from 6He
5H
6He
-1p
p
n
1p3/2
1p3/2
1s1/2
1s1/2
Jp0
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Single-proton Removal from 6He
5H
6He
-1p
p
n
1p3/2
1p3/2
1s1/2
1s1/2
p1s1/2?n(1p3/2)2 j0
Jp0
Jp1/2 g.s.
p1s1/2?n(1p3/2)2 j2
Jp3/2,5/2
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5H Comparison 3-body theory
Cross-talk eliminated
1/2
3/2
5/2
1/2 (plane wave/ no FSI)
Cross-talk included

3-BODY MODEL Shul gina et al.,PRC61(00)014312
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C(6He,tnn) _at_ 240 MeV/nucleon
Meister et al., NUPA723(03)13 3-BODY MODEL
Shul gina et al., PRC61(00)014312

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Two-Neutron Intensity InterferometryHBT Effect
Correlation Function - Cnn

FM Marqués et al., PLB (2000)
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5H Decay tnn Dalitz plot analysis
Dalitz plots and 3-body correlations in
breakup F.M. Marqués et al., PRC64(01)233
Group Exotiques G. Normand et al.
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4H C(6He,tn)X _at_ 30 MeV/u
Er ? 1.9 MeV G0 ? 3.2 MeV
? t 60 fm/c
Group Exotiques - G. Normand et al.
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5H Cnn Gaussian Source
RMS rnn 5.5 1.7 fm
deuteron rnp ? 3.8 fm
Group Exotiques - G. Normand et al.
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and what about the tetraneutron ??
and what about the tetraneutron ??

• Clustering within nuclei
• ? can free An exist ?
• Beyond 2n (Sn -70keV)
• 4n most likely
• 4He(p-,p ), 7Li(11B,14O)
• ? New approach

• Clustering within nuclei
• ? can free An exist ?
• Beyond 2n (Sn -70keV)
• 4n most likely
• 4He(p-,p ), 7Li(11B,14O)
• ? New approach

P. Regan (on numerous occassions after a few
beers)
P. Regan (on numerous occassions after a few
beers)
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Production 14Be (35 MeV/u) C ? 10Be 4n
Sn(14Be) 5.2 MeV

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Detection à la Chadwick


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Detection à la Chadwick
Detection via breakup

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Detection à la Chadwick
Single-neutron response
Detection via breakup

FM Marqués et al., PRC (2002)
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Results 14Be C ? ABe xn

FM Marqués et al., PRC (2002)
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Results 8He C ? AHe xn

Group Exotiques V. Bouchat et al. CHARISSA-DEMON
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Results 8He C ? AHe xn
PRELIMINARY

Group Exotiques V. Bouchat et al. CHARISSA-DEMON
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... 4n as a (low-lying) resonance ?

• Not considered in original
• background/pileup estimates
• Resonance does not live
• long enough to reach
• DEMON ...
• ? Focusing of neutrons
• from decay of 4n
• ? compatible with signal
• but C2S, E, G ??

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Conclusions

• New reaction probe - high-energy nucleon removal
  - and analysis techniques to explore structure
  and correlations at and beyond the dripline
• ? N8 not a closed shell for 12Be (nor for 11Li)
• ? N9 ns1/2 - d5/2 inversion for 13Be (14B, 15C)
  14Be halo
• ? 5H broad Jp 1/2 g.s. (?? yi ? yf )

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Conclusions

• New reaction probe - high-energy nucleon removal
  - and analysis techniques to explore structure
  and correlations at and beyond the dripline
• ? N8 not a closed shell for 12Be (nor for 11Li)
• ? N9 ns1/2 - d5/2 inversion for 13Be (14B, 15C)
  14Be halo
• ? 5H broad Jp 1/2 g.s. (?? yi ? yf )

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Conclusions

• New reaction probe - high-energy nucleon removal
  - and analysis techniques to explore structure
  and correlations at and beyond the dripline
• ? N8 not a closed shell for 12Be (nor for 11Li)
• ? N9 ns1/2 - d5/2 inversion for 13Be (14B, 15C)
  14Be halo
• ? 5H broad Jp 1/2 g.s. (?? yi ? yf )

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Conclusions

• New reaction probe - high-energy nucleon removal
  - and analysis techniques to explore structure
  and correlations at and beyond the dripline
• ? N8 not a closed shell for 12Be (nor for 11Li)
• ? N9 ns1/2 - d5/2 inversion for 13Be (14B, 15C)
  14Be halo
• ? 5H broad Jp 1/2 g.s. (?? yi ? yf )

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Perspectives
5H different yi p(8He,a) MUST_at_SPIRAL
N4
4n d(8He,6Li) MUST_at_SPIRAL (see S.F. talk)
DEMON C(8He,a4n) preliminary results
C(15B,10Be4n) autumn 2005
N7
9He spectroscopy with different yi
C(11Be,8Hen) ? ns1/2 C(14B,8Hen)
? ns1/2 nd5/2
N9
12Li search for low-lying resonances
C(14B,11Lin) ? ns1/2 / nd5/2
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Perspectives
5H different yi p(8He,a) MUST_at_SPIRAL
N4
4n d(8He,6Li) MUST_at_SPIRAL (see S.F. talk)
DEMON C(8He,a4n) preliminary results
C(15B,10Be4n) autumn 2005
N7
9He spectroscopy with different yi
C(11Be,8Hen) ? ns1/2 C(14B,8Hen)
? ns1/2 nd5/2
N9
12Li search for low-lying resonances
C(14B,11Lin) ? ns1/2 / nd5/2
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Perspectives
5H different yi p(8He,a) MUST_at_SPIRAL
N4
4n d(8He,6Li) MUST_at_SPIRAL (see S.F. talk)
DEMON C(8He,a4n) preliminary results
C(15B,10Be4n) autumn 2005
N7
9He spectroscopy with different yi
C(11Be,8Hen) ? ns1/2 C(14B,8Hen)
? ns1/2 nd5/2
N9
12Li search for low-lying resonances
C(14B,11Lin) ? ns1/2 / nd5/2
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Perspectives
5H different yi p(8He,a) MUST_at_SPIRAL
N4
4n d(8He,6Li) MUST_at_SPIRAL (see S.F. talk)
DEMON C(8He,a4n) preliminary results
C(15B,10Be4n) autumn 2005
N7
9He spectroscopy with different yi
C(11Be,8Hen) ? ns1/2 C(14B,8Hen)
? ns1/2 nd5/2
N9
12Li search for low-lying resonances
C(14B,11Lin) ? ns1/2 / nd5/2
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questions ??
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5H Conclusions Perspectives
C(6He,tnn) ? broad structure Ed 2 MeV
(no narrow G) ? consistent with 3-body model
Jpg.s. 1/2 ? reasonable agreement with
GSI C(6He,tnn) ? poorer agreement with RIKEN
p(6He,pp) ? rms Rnn ? 6 fm Moral of the story
... ltyi REACTIONyfgt 2005
... ? p(8He,a) MUST_at_SPIRAL P.
Roussel-Chomaz et al.
see also Grigorenko, EPJ (2004)
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STOP PRESS ... DEMON in Dubna t(t,ptn) _at_ 19
MeV/u
Golovkov et al. PRL 93 (04) 262501
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12Ben Coincidences
Behaviour of virtual s-states
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Acceptance Effects
qn lt 5
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ABe ? 9He yi ? yf
x4
12Be ? 9He 11Be ? 9He x4
12Be ? 9He s, p, d - states
G. Normand, Thèse, LPC (2004)
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High-Energy, Single-Nucleon Removal

• s-1n 10-100mb, rs 100 mg/cm2
• forward focussing

g
ds/dp
T1N
g ? Excore ds/dp ? ?n s-1n(Jpcore) ?
C2S

REVIEW Hansen, Tostevin, Ann. Rev. Nucl. Part.
Sci. (2003)
64
Single-Neutron Removal p-sd shell
43-68 MeV/nucleon 1-600 pps
s-1n 50 - 200 mb FWHM 50 - 240 MeV/c

Expt v s Glauber Theory Shell Model Sauvan,
et al., PRC (2004)
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N8 shell closure - 12Be?
p
n
1p1/2
1p3/2
1s1/2
Closed p-shell in 12Be

Nucleons potential courtesy Jeff Tostevin,
Surrey

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N8 shell closure - 12Be?
1d5/22
n-threshold
p
n
0.32
1/2--
?
2s1/2
0
1p3/2
1/2
11Be
1s1/2
psd-shell ordering in 12Be?
level inversion

Figure courtesy Jeff Tostevin, Surrey
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N8 shell closure C( 12Be,11Beg) _at_ 78
MeV/nucleon
?0
?1
s(1/2-) 183 mb
s(1/2) 325 mb

A. Navin et al., PRL (2000)
68
N8 shell closure C( 12Be,11Beg) _at_ 78
MeV/nucleon
sexpt vs sGlauber ?
?0
C2S (ns1/2) ? 0.5
C2S (np1/2) ? 0.4
?1

A. Navin et al., PRL (2000)