Neutron-skin%20structure%20and%20shell%20evolution%20%20of%20weakly-bound%20neutron-rich%20SPIRAL/SPIRAL2/EURISOL%20nuclei%20%20in%20coupled-reaction%20channel%20studies

1
Neutron-skin structure and shell evolution of
weakly-bound neutron-rich SPIRAL/SPIRAL2/EURISOL
nuclei in coupled-reaction channel studies
Nuclear densities et excitations of exotic nuclei
via direct reactions
ACTIVITIES AND PERSPECTIVES
Structure studies at the drip-lines exemples,
exp-theory
GOAL extension of systematics of neutron rms
radius and of neutron
excitation along isotopic
chains
?n , ?p

• Probe the structure spectroscopy at large
  isospin
• Measure unbound states ? detection devices

NEED FOR AN IMPROVED THEORETICAL FRAMEWORK
OF STRUCTURE AND REACTIONS
2
Nuclear structure towards the drip-lines
phenomena to explore to understand
Evolution of structure at large isospin ?
Drip-lines limit of nuclear binding, large
isospin Exploration new exotic structures ?
neutron-skin Tests nuclear modelling
interactions VNN(Tz)
Weakly bound states ? Continuum coupling
? Isospin dependence ?
2008 what do we know? 2016 future explorations
3
Nuclear landscape towards the drip-lines
Nuclear landscape towards the drip-lines
2008
Testing ground
Very few drip-line nuclei have their identity
card complete ? Masses, size, densities, neutron
excitation, low-lying spectroscopy, shell
structure
Drip-line 8He neutron-skin
SPIRAL 8He (T1/2 119ms) I 104 /s E15.7 A.MeV
reaction target CH2
4
SPhN activities on structure of exotic nuclei
via direct reactions

• Objectives
• evolution of nuclear structure at large N/Z
• ? nuclear correlations, p-n interaction
• exploration of new phenomena
• - tests of the validity of the models

Method direct reactions induced by radioactive
beams GANIL/SPIRAL SPIRAL2 in 2012
5
Light nuclei and three-body forces
S. Pieper et al. Nucl Phys. A751(2005), 516c PRC
70 (2004) 54325
6
Structure of 8He extracted from direct reactions
on proton target
SPIRAL 8He p _at_ 15.7A.MeV
F. Skaza PhD SPhN F. Skaza, N. Keeley, VL et al.,
PLB 619. 82 (05) N. Keeley et al., PLB
646,222(07)
Coupled-channel calc. N. Keeley (SPhN)

• Structure of ground state search for unbound
  excited states
• ? spectroscopy of light charged particles p,d,t
  (MUST)
• ? measurements of resonances in 8He NPA 788c,
  260 (07)
• angular distributions analysis in coupled
  reaction channels
• PLB 619. 82 (05) 646, 222 (07)

7
Structure of 8He extracted from direct reactions
on proton target
1 8He(p,d)7He C2S 4.4 1.3
CCBAanalysis CRC (p,p) (p,d) C2S 3.3
1.3 PLB 619, 82 (05)
CRC Coupled-reaction channel analysis N. Keeley
(SPhN, Inst. A. Soltan)
2 (p,t)? wf. of 8He6He 8He/6He(0) 1
8He/6He(2) 0.014
Consistent with results from quasi-free
scattering of 8He measured at GSI, LV Chulkov
et al, NPA759, 43(05)
Configuration mixing (p3/2)4 and (p3/2)2
(p1/2)2
Data SPIRAL-MUST 1 F. Skaza et al., PRC73,
044301(07) 2 N. Keeley et al, PLB 646, 222(07)
8
Spectroscopy of 8He exp versus theory
Kor93 A.A. Korsheninnikov et al., PLB 316 (93)
38 Oer95 W von Oertzen et al., NPA588 (95)
129 Nil95 T. Nilsson et al., NPA583 (95)
795 Boh99 H.G. Bohlen et al., Prog. Part. Nucl.
Phys. 42 (99) 17 Mar01 K. Markenroth et al.,
NPA679 (01) 462
Wir02 R.B. Wiringa S.C Pieper, PRL 89 (02)
182501 Nav04 P. Navratil B.R. Barrett, PRC
57 (98) 3119 private co.
9
Spectroscopy of 8He exp versus theory
And the specific treatment of resonant states ?
Wigner  Beautiful theories have to face ugly
facts
10
Spectroscopy of 8He exp versus theory
Gamow Shell Model (GSM) consistent description
of bound states and the particle continuum
(resonances and the non-resonant scattering
background). N. Michel et al., PRL 89, 042502
(02) PRC 67, 054311 (03) ?The gs is bound
by CC correlations
Continuum Shell Model (CSM) Discrete and
Continuum Spectra in the Unified Shell Model
Approach, A.Volya V. Zelevinsky, PRL 94,
052501 (05)
QMC NCSM GSM CSM
11
Conclusions
conclusions ... prospectives
Test of the validity of 8He gs densities using
(p,p) neutron-skin features close to NCSM
densities COSMA not valid
NEUTRON-SKIN THICKNESS 0.6 /- 0.05 fm
12
Participants of the experiment 8He(p,p)
SPIRAL E405S
CEA-SACLAY DSM/DAPNIA/SPhN N.
Alamanos, F. Auger, A. Drouart, A. Gillibert, V.
Lapoux, L. Nalpas, E. Pollacco, R.
Raabe, J-L. Sida, F. SKAZA (PhD). IPN-Orsay D.
Beaumel, Y. Blumenfeld, F. Delaunay, E. Becheva,
J-A. Scarpaci Ganil L. Giot, P.
Roussel-Chomaz FLNR - Dubna S. Stepantsov, R.
Wolski University of Ioannina A. Pakou
INTERPRETATION
ANALYSIS Microscopic densities P. Navrátil
interaction Argonne H. Sagawa HF
correlations Futur cf M . Ploszajczak Ganil
JLM potential code Dietrich (Livermore) form
factors (home made, VL) CRC calc.
N. KEELEY With the Fresco code (IJ Thompson,
Surrey Univ).
COLLABORATION MUST2
CEA DAPNIA, GANIL, IPN-Orsay

• DAPNIA SEDI E. Atkin, P. Baron, F. Druillole, F.
  Lugiez, B. Paul, M. Rouger
• SPhN A. Drouart, A. Gillibert, V.
  Lapoux, L. Nalpas, E. Pollacco
• IPN-Orsay SED P. Edelbruck, L Lavergne, L.
  Leterrier, A. Richard, M. Vilmay, E. Wanlin,
• Structure Y. Blumenfeld, D. Beaumel, E. Becheva
• GANIL GIP M. Boujrad, L. Olivier, B. Raine, F.
  Saillant M. Tripon, Physics P. Roussel Chomaz

13
Collaboration
Structure spectroscopy of exotic nuclei
E525S
6He low-lying spectroscopy via 8He(p,t)6He
DAPNIA/SPhN N. Alamanos, F. Auger, A. Drouart,
A. Gillibert, N. Keeley, V. Lapoux, X.
Mougeot (TH), L. Nalpas, E. Pollacco, C. Simenel
IPN-Orsay D. Beaumel, Y. Blumenfeld, J.
Guillot, J-A. Scarpaci Visiteurs à Orsay H.
Iwasaki, D. Suzuki GANIL P. Roussel-Chomaz, C.
Force, L. Gaudefroy, T. Kalanee, T. Roger A.
Soltan, Varsovie K. Rusek, I. Strojek FLNR -
Dubna R. Wolski University of Ioannina
A. Pakou, T. Mermizedakis
Technical and software support ASIC DAPNIA/SEDI
E. Atkin, P. Baron, F. Druillole, F. Lugiez, B.
Paul, M. Rouger
Technical and software support SPEG P. Gangnant,
JF Libin Ganil, services techniques J.
Cacitti, G. Fremont, C. Spitaels GIA ex GIP C.
Houaner, G. Leberthe, L. Légeard, L. Olivier, M.
Tripon, B. Raine, F. Saillant
14
Nearfarfutureprojectsplans
15
MUST2 MUr à STrips 2, new generation of MUST
MEASUREMENTS AND ANALYSIS OF REACTIONS IN
COUPLED- CHANNELS
Present techniques
16
Spectroscopy of 6He
THEORIES
17
Experimental set-up with MUST2
CH2 target 1mg/cm2
SISSI-SPIRAL Beams 8He, 20,22O, 14O I 104 - 105
/s
Identification A,Z SPEG
p,d,t
MUST2
MUST2 _at_ d15 cm 5-25 deg lab (15-80 c.m.) Sect.
Eff (p,t) 5 10-3 0.5 mb/sr
CATS2
18
Structure of exotic nuclei via direct reactions
Transfer reactions coupling between particle
and gamma spectroscopy
Complete kinematical reconstruction access to
bound and unbound states
Charged-particle spectroscopy Thin target CH2 ,
CD2 1 mg/cm2
I (gt 5. 103/s)
ex SPIRAL2 96Kr _at_ 10MeV/n I 104 /s
96Kr(d,p)97Kr, (d,d) (d,t) EURISOL n-rich Ne,
Ca, Ni, Kr, Sn _at_ 20-50MeV/n I gt 105 /s
AZ(d,p)A1Z
AZ
19
Nuclear landscape towards the drip-lines
Nuclear landscape towards the drip-lines
2008
Testing ground
18
Z
07 125Pd (Z46) found at RIBF
16
43Si
44Si
14
Low-lying resonances ? Neutron skin ? Neutron
excitation ? Density Profiles ? New shell effects
?
34Mg
38Mg
40Mg
12
33Na
37Na
4He
10
30,31,32Ne
34Ne
Tarasov97 Sakurai PLB448, (99) Notani PLB 542
(02), Lukyanov02 Tarasov PRC 75 (07)
31F
8
24O
structure of 24O ?
23N
Drip-line
? Complete the Identity card of drip-line nuclei
22C
20
Shell effects far away from stability with new
generations of RIB s
systematics of neutron excitations vs N Search
for new magic numbers
21
Spectroscopy of unbound states in neutron-rich
beams close to the drip-lines
Which beams ? We want to gain in exoticity
Complete the (p,p) chains O (24O), Ne Mg,
Si, S, Ar spectroscopy of neutron-rich
nuclei around doubly magic Z28, N40,50 Z50,
N82 around N28, N40 (possible new magic),
N50, N70 (new)
Examples 34Ne , 38Ne (if not unbound), 60-70Ca,
104Se (Z34, N70)
If the beams are new (36Ne ? 60-68Ca ?) or rare
at present (24O few/s at GANIL, RIKEN) with
EURISOL counting rates less or around 103-105 /s
22
Unbound states in neutron-rich nuclei via direct
reactions
Letter of Intent for SPIRAL2
o Single-particle structure o Nuclear pairing o
Spectroscopy of very-neutron rich nuclei o
Cluster studies o Direct reaction mechanisms o
Applications to astrophysics ? cf LOI r
process nucleosynthesis
Cf GENERAL LOI Direct Reactions Studies of
Exotic Nuclear Structure
- Experimental conditions and requirements
BEAM, DETECTION, THEORY - SPECIFICITY
LOI-16 unbound states in n-rich nuclei
23
Going closer to driplines with higher intensities
opened physics fields
Far ..far away
24
Low-lying spectroscopy of n-rich Kr isotopes
Neutron excitation of 96Kr via (p,p) and shell
structure of 97Kr via 96Kr(d,p)
Bound and unbound states ? full reconstruction of
the kinematics ? (p,p) or (d,p) excitation
spectrum Spectroscopic factors
ISPIRAL2
94Kr I gt 109 0.75 MeV
95Kr I gt 9. 108 2.84 MeV
96Kr I gt 104 0.74 MeV
Q-value
25
LOI Unbound states
PREPARATION OF THE EXPERIMENTAL SET-UP
BTD particle-gamma coupling Detection at the
focal plane for (Z,A) identification

• separation of excited states
• with high-density level
• cf LOI-direct Reactions
• Future 4? GASPARD array
• GAmma Spectroscopy
• PArticle Detection
• simulation of exp set-up

26
Collaboration LOI SPIRAL2 Unbound states
CEA-SACLAY DSM/DAPNIA/SPhN N. Alamanos, F.Auger,
R.Dayras, A. Drouart, A. Gillibert, N. Keeley,
V. Lapoux, L. Nalpas, E. Pollacco, C. Simenel, X.
Mougeot. IPN-Orsay D. Beaumel, S. Fortier, F.
Hammache, E. Khan, C. Petrache GANIL L.
Gaudefroy, W. Mittig, F. de Oliveira, P.
Roussel-Chomaz, H. Savajols, O. Sorlin HMI
Berlin, Germany H.G. Bohlen, Tz. Kokolova, W.
Von Oertzen, C. Wheldon JINR, FLNR Dubna, Russia
A. Fomichev, M.S. Golovkov , A. Rodin, S.
Sidorchuk, S. Stepantsov, G. Ter-Akopian, R.
Wolski IKS University of Leuven, Belgium R.
Raabe IPHC Université Louis Pasteur, Strasbourg
Ch. Beck, S. Courtin, A. Khouaja INFN-Catania,
Italy A. Musumarra KVI, Netherlands M.N.
Harakeh, H.G. Wortche Florida State University,
US K.Kemper University of Huelva, Spain I.
Martel University of Ioannina, Greece T.J.
Merzimekis, A. Pakou, D. Roubos University of
Santiago de Compostela, Spain M.D
Cortina-Gil Theoretical support
CEA-Bruyères-le-Châtel DAM/DIF/SPN E. Bauge,
P. Chau Huu-Tai, J.P. Delaroche, H. Goutte,
S.Péru CENBG M. Bender IPN-Lyon K.
Bennaceur IST, Lisboa, Portugal R. Crespo The A.
Soltan Institute for Nuclear Studies, Hoza,
Warsaw, Poland K. Rusek NSCL, MSU, USA T.
Duguet University of Pisa-INFN-Pisa G. Blanchon,
A. Bonnacorso The Open University, UK R.S.
Mackintosh University of Sevilla, Spain A.M.
Moro VAEC Hanoï, Vietnam Dao. T. Khoa INST
Hanoï Hoang S. Than
27
ANALYSIS OF (D,P) CROSS SECTIONS...
Once upon a time Successful analysis for the
stable nuclei cf 40Ca(d,p) E7, 8, 9,10, 11,
12 MeV Lee,..Schiffer, Satchler, Drisko, PR 136
4B (64) 40Ca(d,p) 41Ca a test of the validity of
the DWBA R. Satchler Direct nuclear reactions,
Clarendon Press, Oxford Univ Press 1983
 The DWBA was shown to be inappropriate for the
analysis of (d, p) reactions some 30 years ago,
due to the importance of the deuteron breakup
channel. 
We know that average properties
parameterizations are working for stable beams
(300 species) ONLY SMALL PART of all 2000 RIB,
even more 3000 possible ones
DO THE BEST POSSIBLE CALCULATIONS !!!! DWBA is a
limited framework, turns out to be WRONG for
strongly-coupled channels cf CRC calculations,
CDCC Nick Keeleys lecture at ECOLE JOLIOT-CURIE
07 les réactions nucléaires comme sonde de la
structure
28
EURISOL a new theoretical framework
Probe for the structure (p,p) But flux shared
between several reaction channels ? elastic and
transfer reactions competition between main
reaction channels NEED TO DEFINE THE APPROPRIATE
SCATTERING THEORY
State of the art Coupled reaction channel
analysis ? explicit channel coupling Microscopic
potentials
FUTURE Structure and reaction on the same footing
29
EURISOL a new theoretical framework
Data Virtual coupling potential for elastic
scattering of 10,11Be on p V. L et al., PLB
658, 198 (08)
30
Drip-line studies
SPIRAL2, RIBF, EURISOL
FIND NEW REGIONS OF INTEREST ? Nuclei with large
matter extension (neutron-skin,
superdeformation) ? New shell gaps

• EXTENSION OF the systematics of neutron
  excitation along isotopic chains
• MEANS to Probe the structure spectroscopy at
  large isospin
• Measure unbound states
• ? EXPLORATION

Spectroscopy of low-lying resonances, unbound
states, neutron excitation, exotic excitation
modes soft dipole resonance and transition
densities Halo,skin features of weakly-bound
exotic nuclei
local shell change like N16 (34, 70..)
indicated by Ex(2), B(E2) S2n, and evolution
of neutron excitation
SIMPLE PROBE (p,p) combined to Coulex
information direct reactions in inverse
kinematics, missing mass method
31
spectroscopy of low-lying states of neutron-rich
isotopes via (p,p), (p,d) (p,t), (d,p)
FUTURE WORKS
Improvment of exp set-up Theoretical framework
Present (1st generation) intensities few
part/s Needed (at least) 103-105 /s

• Measurement to unbound states
• Particle-spectroscopy
• Large enough intensities ? EURISOL
• Large angular coverage
• all reactions measured simultaneously
• Elastic and transfer
• Low particle threshold small c.m. angles
• Possible to carry out
• full coupled-reaction channel analysis
• EXTRACT form factors from (p,p)
• spectroscopic factors from (d,p)

suitable range of beam energies for (p,p) and
(d,p) E 10-30 MeV/n
In 2016 new beams of neutron-rich Ne, Ca, Ni,
Kr, Sn isotopes ? Access to neutron-thickness
evolution change in shell structure
32
Theoretical framework for the analysis of direct
reactions
PROTOTYPE-STUDY 8He(p,p) (p,d) PLB 619,
82(05)
Usual framework DWBA, not valid, need to operate
with CRC
The usual ingredients and models based on past
studies for stable nuclei must be put into
question A PRIORI How good (potential,
framework) is really good for exotic beams
? Validity of optical potentials ? Examine the
assumptions in the case of weakly-bound nuclei or
for specific coupling (large spectroscopic
factors, enhanced excitation etc..) To be
checked by measuring carefully the elastic
scattering , ?TESTING GROUND FOR THE INTERACTION
POTENTIAL AND THE REACTION MODEL

• Enhanced effects in the case of weakly-bound
  exotic nuclei
• Coupling to continuum, 3-body, many-body
  correlations
• Shell structure embedded in the continuum
• Use the predictions of improved structure
  theories to take into account
• these effects and the isospin-dependence of the
  nuclear interaction

To be scheduled in 2008 ESNT Workshop STRUCTURE
AND REACTIONS IN COUPLED REACTION CHANNELS
33
Conclusions Perspectives
Structure and spectroscopy of exotic nuclei via
direct reactions
Powerful tool for the study of unbound states
DIRECT REACTIONS IN COUPLED CHANNELS
MUST2
PHYSICS OF THE PUZZLE AND OF THE INTERPLAY
 MOSAÏQUE DES NOYAUX , P. BONCHE, CEA-SPhT
Studies of exotic nuclei need to combine several
probes Require systematics along extended
isotopic chains
34
Discussions - Questions
the force ?
 On the theoretical side, we are lacking a
derivation of the nuclear force that is based
upon theory (in the true sense of the word) and
produces a quantitative NN potential  R.
Machleidt and I. Slaus, The nucleon-nucleon
interaction, TOPICAL REVIEW J. Phys. G Nucl.
Part. Phys. 27 (2001) R69-R108
sp states Couplings collective degrees of
freedom ?
 In all the recent works devoted to the
single-particle states the particle-vibration
coupling is mentioned but not taken into account
so far within the same framework. A serious
step forward in this direction has to be made. 
W. Zou, G. Colo, Z. Ma, H. Sagawa and PF
Bortignon, Tensor correlations and evolution of
single-particle energies in medium-mass nuclei,
Phys. Rev. C 77, 014314(2008)
Reaction structure? Revisit scattering theory?
Treatment of the structure embedded in the
continuum, of the unbound states ?
Extended framework treating on the same footing
bound and scattering states ?
35
Open questions
Structure theories for states embedded in the
continuum ?
We need theories with structure and reaction
embedded in the continuum
36
Conclusions
37
Compléments (I)
38
Structure of exotic nuclei
Rules of the evolution of nuclear structure at
large isospin ?
? Experimental exploration
39
Predictions of the Drip-lines
40
Predictions of the drip-lines, HFB-Skyrme
microscopic predictions for S2n energy and
deformation throughout the mass table
Density functional method Sly4 Skyrme NN
interaction
J. Dobaczewski et al.
M.V. Stoitsov, et al., PRC68, 054312 (03)
41
Reference calc from PRCStoit03
42
Unbound states of exotic nuclei
Similar trend for neutron-rich SPIRAL2 beams
few bound states
Calc M.V. Stoitsov, et al., Phys. Rev. C68,
054312 (03) Data AME2003
43
Predictions of the Drip-lines, HFB-Gogny
M. Girod et al, CEA-DAM
44
Predictions of the Drip-lines, RMF
125Pd (Z46) found at RIBF, N79
45
Compléments (II)
46
Nuclear structure explored via elastic and
inelastic scattering (p,p)
Testing ground weakly-bound light nuclei
Weakly bound states ? Continuum coupling
? Isospin dependence ?
47
Search for low-lying resonances and study of
neutron excitations
(p,p) probe Particle spectroscopy
Present techniques results
structure studies by (p,p) (p,d) reactions
using GANIL/SISSI or SPIRAL beams and MUSTCATS
Inelastic scattering sensitive to the shape
of the density
Elastic scattering sensitive to the matter rms
Nuclear densities, neutron excitation
C.Jouanne, VL. et al., 10,11C(p,p) PRC 72,
014308 (05)
rmsm (10C) 2.42 ? 0.1 fm rmsm (11C) 2.33 ?
0.1 fm rmsm (12C) 2.30 (3) fm
Weakly-bound nuclei Unbound excited
states low-lying resonances
exotic He isotopes
MUST Y.Blumenfeld et al., NIM A421, 421 (99)
CATS S. Ottini et al., NIM A431, 476 (99).
Halo, Neutron-skin structure
48
Prototype of (p,p) direct reactions at low
energy 8He(p,p)
8He (T1/2 119ms) I 104 /s reaction target CH2
set-up at GANIL
PROBE 8He(p,p)8He
? test of the validity of the densities eg
6He(p,p) _at_ 40.9 MeV/n GANIL-MUST A. Lagoyannis
et al., PLB 518, 27 (01) 2n-Halo features 6He
NPA722, 49c(03)
Collaboration SPhN, GANIL, IPN-Orsay,
FLNR-Dubna, Univ. Ioannina (Greece)
49
Structure of 8He models
B(E2) 0.25e²fm4 Mn/Mp 13.5
COSMA M.V. Zhukov, A.A Korsheninnikov M.H
Smedberg, PRC 50 (94) R1 H. Sagawa, PLB 286
(92) 7
P. Navratil W.E. Ormand, PRL88, 152502 (02)
priv. Co.
50
Conclusions structure and spectroscopy of 8He
(p,p) (p,d) (p,t) _at_ 15.7 A.MeV
SPIRAL
8He(p,p) E 2 states
All direct reactions at the same energy a need
for a complete coupled-channel analysis
51
SPhN - Exotic nuclei Structure and
spectroscopy of8He via direct reactions on proton
SPIRAL 8He (T1/2 119ms) I 104 /s E15.7 A.MeV
reaction target CH2

• Structure de létat fondamental
• recherche détats excités non liés
• ? spectroscopie de particules légères chargées
  p,d,t (MUST)
• ? mesures des résonances de 8He
• NPA 788c, 260 (07)
• distributions angulaires
• ? analyse en voies couplées des réactions
• PLB 619. 82 (05) 646, 222 (07)

52
Evolution of the neutron skin thickness ex of
Neon isotopes
Density functional.calc. with R. Lombards code
Similar trend in HFB-def (Sly4) calc of J
Dobaczewski, M.V. Stoitsov, et al., PRC68,
054312(03)
53
Neutron-skin structure of 34Ne via direct
reactions on proton target
34Ne(p,p)34Ne
34Ne p ? p 34Ne ? p 32Ne 2n
p 34Ne ? p 30Ne 4n