probe the structure & spectroscopy at large isospin measure unbound states detection devices

Direct reactions to unbound states ESNT 4-6Fev. 08 CEA-SPhN [email protected]

Neutron-skin structure and shell evolution

of weakly-bound neutron-rich SPIRALSPIRAL/SPIRAL2SPIRAL2/EURISOLEURISOL nuclei

in coupled-reaction channel studies

Probe the structure & spectroscopy at large isospinMeasure unbound states detection devices

n , p

GOAL: extension of systematics of neutron rms radius and of neutron excitation along isotopic chains

Structure studies at the drip-lines : exemples, + exp-theory

NEED FOR AN IMPROVED THEORETICAL FRAMEWORK NEED FOR AN IMPROVED THEORETICAL FRAMEWORK OF STRUCTURE AND REACTIONSOF STRUCTURE AND REACTIONS

ACTIVITIES AND PERSPECTIVES

Nuclear densities et excitations of exotic nuclei via direct reactions


Nuclear structure towards the drip-lines : phenomena to explore & to understand

Neutron skins

halo,clusters

Change in shell structureNew magic numbersLocal properties (N,Z)

4He

6Hehalo

8He4He

Neutron skin

Evolution of structure

at large isospin ?

2008: what do we know?2016: future explorations

Drip-lines: limit of nuclear binding, large isospinExploration: new exotic structures neutron-skin Tests: nuclear modelling & interactions VNN(Tz)

Weakly bound states ?Continuum coupling ?Isospin dependence ?


Nuclear landscape towards the drip-lines

2 4 6 8 10 12 14

N

16

2

4

6He

6

Z8

4He

borromeanHe

C

N

O

Hn

pp d t8He

11Li

F 31

Li

Be14Be

B

12

1922

23

24

20020088

Very few drip-line nuclei have their identity card complete Masses, size, densities, neutron excitation, low-lying spectroscopy, shell structure

6He

Drip-line : 8He neutron-skin

SPIRAL 8He (T1/2= 119ms)

I= 104 /s ; E=15.7 A.MeV reaction target CH2


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

Shell structure far from thevalley of stability

N

Z

halo and neutron-skin

8He

6HeMethod : direct reactions induced by radioactive beamsGANIL/SPIRAL ; SPIRAL2 in 2012

SPhN activities on structure of exotic nuclei via direct reactions

Experimental DevicesDetector of

Charged particlesSi-strips, CsI

x-y-E-DE-TOF

MUST2Collaboration:

DAPNIA, GANIL and IPN-Orsay

Beam detectorCATS-BTD

SEDI-SPhN targ

et

10 cmbeam


Light nuclei and three-body forces

S. Pieper et al. Nucl Phys. A751(2005), 516c

PRC 70 (2004) 54325


SPIRAL 8He +p @ 15.7A.MeV

Structure of Structure of 88He extracted from direct reactions on proton targetHe extracted from direct reactions on proton target

F. Skaza PhD SPhNF. Skaza, N. Keeley, VL et al., PLB 619. 82 (’05)N. Keeley et al., PLB 646,222(’07)

Coupled-channel calc.: N. Keeley (SPhN)

8He(p,p) 8He(p,t)6He(0+)

8He(p,t)6He(2+)

8He(p,d)

CRC calc

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 channelsPLB 619. 82 (’05) ; 646, 222 (’07)


[1] 8He(p,d)7He C2S = 4.4 ± 1.3 [CCBAanalysis]CRC (p,p) (p,d) C2S = 3.3 ± 1.3PLB 619, 82 (’05)[2] (p,t) wf. of 8He%6He [8He/6He(0+)] =1 ;[8He/6He(2+)] =0.014

Configuration mixing : (p3/2)4 and (p3/2)2

(p1/2)2

Structure of Structure of 88He extracted from direct reactions on proton targetHe extracted from direct reactions on proton target

Consistent with results from quasi-free scattering of 8He measured at GSI, LV Chulkov et al, NPA759, 43(’05)

Data: SPIRAL-MUST [1] F. Skaza et al., PRC73, 044301(’07)[2] N. Keeley et al, PLB 646, 222(‘07)

CRC Coupled-reaction channel analysis: N. Keeley (SPhN, Inst. A. Soltan)

CRC calc

8He(p,t)6He(0+)

8He(p,t)6He2+

8He(p,d)8He(p,t)6He(0+)

8He(p,t)6He (2+)

Data: A. A.Korsheninnikov et al, PRL 90, 082501 (‘03)

RIKEN 61.3 A.MeV

CRC calc p n1s1/2

1p3/2

1p1/2

p n1s1/2

1p3/2

1p1/2


Spectroscopy of Spectroscopy of 88He : exp versus theoryHe : 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.

experiments

theories

(p,p’)

[Kor93] [0er95] [Nil95] [Boh99] [Mar01]

COSMA model +4nM. Zhukov et al. PRC50,

1(‘94)

p n1s1/2

1p3/2

1p1/2



Wigner : « Beautiful theories

have to face ugly facts »

And the specific treatment of resonant states ?

experiments theories

[Kor93] [0er95] [Nil95] [Bohl99] [Mark01]

(p,p’)

SPIRAL(p,p’)

E(MeV) Γ (MeV)2+ 3.62 ± 0.14 0.3 ± 0.2? 5.4 ± 0.5 0.5 ± 0.3



P. Navrátil & B. R. Barrett,

PRC 57, 3119 (‘98).“The 8He nucleus is a weakly bound

system, where scattering to the continuum

will play an important role in the structure of higher-lying states.”

Continuum Shell Model (CSM):Discrete and Continuum Spectra in the Unified Shell Model

Approach, A.Volya & V. Zelevinsky, PRL 94, 052501 (‘05)

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

[QMC] [NCSM] [GSM] [CSM]


Alpha + 4 n

No coreShell model

Conclusions

Test of the validity of 8He gs densities using (p,p) : neutron-skin features close to NCSM densities COSMA not valid

(p,p’) mainly sensitive to the neutron excitation ; Transition densities 2+ 0+ : NCSM calc. overestimate the p & n excitations

n , p

(p,p’)(p,p’)

NCSM2.462.592.00NCSM, Navrátil

2.512.671.95HF+corr Sagawa

2.522.741.69 COSMA 5-body

MatterNeutronProton

Rms (fm)8He

NCSM (No Core Shell Model) (V3eff 4hw, 13MeV )

Test of transition densities ; Analysis in progress

CRC (p,p’) CRC (p,p’) Coupling with the Coupling with the (p,t)(p,t)

NEUTRON-SKIN THICKNESS: ~ 0.6 +/- 0.05 fmNEUTRON-SKIN THICKNESS: ~ 0.6 +/- 0.05 fm

Validation of no-core shell model calculations (NCSM) for gs

COSMA:Alpha+4n


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. ScarpaciGanil : L. Giot, P. Roussel-ChomazFLNR - Dubna : S. Stepantsov, R. Wolski University of Ioannina : A. Pakou

Participants of the experiment 8He(p,p’)

ANALYSIS : Microscopic densitiesMicroscopic densities P. Navrátil + interaction Argonne

H. Sagawa HF +correlationsFutur : cf M . Ploszajczak Ganil

JLM potential:JLM potential: code Dietrich (Livermore) ; form factors (form factors (home madehome made, VL), VL) + CRC CRC calc. N. KEELEY

With the Fresco code (IJ Thompson, Surrey Univ).

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


Collaboration

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. ScarpaciVisiteurs à Orsay : H. Iwasaki, D. SuzukiGANIL : P. Roussel-Chomaz, C. Force, L. Gaudefroy, T. Kalanee, T. RogerA. Soltan, Varsovie : K. Rusek, I. StrojekFLNR - Dubna : R. Wolski University of Ioannina : A. Pakou, T. Mermizedakis

6He low-lying spectroscopy via 8He(p,t)6He

Structure & spectroscopy of exotic nuclei

Technical and software support:SPEG P. Gangnant, JF Libin Ganil, services techniques J. Cacitti, G. Fremont, C. SpitaelsGIA ex GIP : C. Houaner, G. Leberthe, L. Légeard, L. Olivier, M. Tripon, B. Raine, F. Saillant

Technical and software support:ASIC DAPNIA/SEDI E. Atkin, P. Baron, F. Druillole, F. Lugiez, B. Paul, M. Rouger


Nearfar

future

projectsplans


100 mm

MUST1 MUST2: improvments factor 3 in active area smaller volume of PAmp : x 6 better time resolution

MUST2 MUr à STrips 2, new generation of MUST

Increased compacity due to the ASIC technology (Application Specific Integrated Circuit) coïncidences particle -

Si(Li)Si(Li)4.5 4.5 mmmm

CsI 3 cmCsI 3 cm4 x 4 4 x 4 segmentssegments

Si stripsSi strips300 300 mm100 x 100 mm100 x 100 mm22

X, Y , T, E128X128Y

E

MUST2MUST22004-62004-6Developed by : DAPNIA/SEDI : µ-electronics R&D ASIC GANIL IPN Orsay

collaboration : CEA-DAPNIA, GANIL, IPN-Orsay

MEASUREMENTS AND ANALYSIS OF REACTIONS IN COUPLED- CHANNELS

collaboration MUST2:SPIRAL +Futur SPIRAL2

Evolution of neutron excitationMn vs N along isotopic chains

Exotic shapes and resonances

One-particle stateSpectroscopic factors

MUST2MUST2


Danilin et al.Few-Body modelPRC 55, 577 (’97)

0+

2+ 1.8

4.3

(2+2) = 1.2

2+2

5

4.51+

0+2

THEORIES

States between 2 and 10 MeV ?

Positions 2+2, 0+

2 VNN +VNNN

Correlations in light neutron-rich nuclei

Navratil et al.No Core shell Model10hw V2eff

0+

2+ 2.53

5.79

2+2

0+2 8.5

4

6.50

1+

Pieper et al.NN+NNN IL2 PRC70,054325(’04)

0+

2+ 1.8

~51+

2+

0+ 6

Spectroscopy of 6He


Experimental set-up with MUST2

CH2 target1mg/cm2

CATS2 CATS1

SISSI-SPIRAL Beams8He, 20,22O, 14OI = 104 - 105 /s

p,d,t

Identification A,Z : SPEG

MUST2

CATS2

MUST2 @ d=15 cm

5-25 deg lab (15-80 c.m.)Sect. Eff (p,t) ~ 5 10-3 – 0.5 mb/sr


Structure of exotic nuclei via direct reactions

BTD

Beam tracking

ex : SPIRAL2 96Kr @ 10MeV/n I= 104 /s 96Kr(d,p)97Kr, (d,d’) (d,t)

EURISOL n-rich Ne, Ca, Ni, Kr, Sn @ 20-50MeV/n I > 105 /s

Complete kinematical Complete kinematical reconstruction reconstruction access to bound and unbound access to bound and unbound statesstates

Ex: MUST2-like arrayParticle-spectroscopy (d,p)

VAMOS

Identification : VAMOS

(d,p) A+1Z

Charged-particle spectroscopyThin target CH2 , CD2 1 mg/cm2

I (> 5. 103/s)

(d,p) Gamma detection

AZ(d,p)A+1Z

AZCD2

p

Transfer reactions ; coupling between particle and gamma spectroscopy


Nuclear landscape towards the drip-lines

16 18 20 22 24 26 28

N

30

18

Z

4He

20020088

10

12

14

16

8 structure of 24O ? 24O23N22C

31F

30,31,32Ne

33Na

34Mg 38Mg

Next drip-line nuclei ?

37Na36

33

39

Tarasov97Sakurai PLB448, (99)Notani PLB 542 (02),Lukyanov02Tarasov PRC 75 (’07)

43Si

40Mg

44Si

Low-lying resonances ?Neutron skin ?Neutron excitation ?Density Profiles ?New shell effects ?

Complete the Identity card of drip-line nuclei

34Ne

Dri

p-l

ine

Dri

p-l

ine

07 :07 : 125 125Pd (Z=46) found at RIBFPd (Z=46) found at RIBF


neutrons

fp

sd

d5/2

d3/2

s1/2

stability

f7/2

p3/2

sd-fpsd-fp 2020

N = 16Z=14 30Si

N = 20

88

N = 8p3/2

p1/2

s1/2

Shell effects far away from stability with new generations of RIB s

systematics of neutron excitations vs N Search for new magic numbers

neutrons

fp

sd

d5/2

d3/2

s1/2

drip-line N = 16, Z=8, 24O

f7/2

p3/2

sd-fp

N = 14 22O

N = 16

N = 8

16

N=16 Learnt from 1st generation of RIBs

(1h11/2-)1

2

82(f7/2) Local properties (Z,N)

N=34,40,70 instead of N=50,82 ?

RIBF, SPIRAL2 EURISOL

Extension of the systematics of neutron excitation along isotopic chains

EURISOL

EURISOL

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

Spectroscopy of unbound states in neutron-rich beams close to the drip-linesWhich beams ? We want to gain in exoticity 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 Z=28, N=40,50 ; Z=50, N=82 around N=28, N=40 (possible new magic), N=50, N=70 (new)

Examples :34Ne , 38Ne (if not unbound), 60-70Ca, 104Se (Z=34, N=70)

Z

N


Letter of Intent for SPIRAL2

o Single-particle structureo Nuclear pairingo Spectroscopy of very-neutron rich nucleio Cluster studieso Direct reaction mechanismso Applications to astrophysics cf LOI r process nucleosynthesis

- Experimental conditions and requirements: BEAM, DETECTION, THEORY- SPECIFICITY

Cf GENERAL LOI : Direct Reactions Studies of Exotic Nuclear Structure

LOI-16 unbound states unbound states in n-rich nucleiin n-rich nuclei

SPECTROSCOPY SPECTROSCOPY of of bound and bound and unboundunbound states states

()

Sn

?E (MeV)

Transfer (d,p) & (p,d)Elastic & Inelastic scattering(p,p’) (d,d’)


Evolution of neutron excitationMn vs N along isotopic chains

Exotic shapes and resonances

One-particle stateSpectroscopic factors

Beams Variety A,ZLimit of nuclear binding, I

2012+ 2020+

Alpha-clustersstates

Skin and halos

Soft collective modesZ

N

Going closer to driplines with higher intensities : opened physics fields

Far ..far away

Sn

134-136Sn94-96Kr94-96Zn 96-98Sr

5

3

4

1

2

Unbound statesMeV

(p,p’), (p,d) (p,t) (d,d’) (d,p) (d,t)

e.g. Ni, 30Zn, 34Se, 36Kr, Sn

-Exc spectra, density distributions via (p,p’)- Shell structure, s.p states, J

via nucleon-transfer


ISPIRAL2 94Kr I > 109

0.75 MeV

95Kr I > 9. 108

2.84 MeV

96Kr I > 104

0.74 MeVQ-value

2.97#

1/2(-)

94Kr(d,p) 95Kr

E

(MeV

)

Sn

gs0

2

95Kr(d,p) 96Kr 96Kr(d,p) 97Kr

S2n

Sn

(7/2-) ?

2.96#

4

00+

4+ ?

2+ ?

6+ ?

?

?

88.03#

Sn5.06#

2+ , 4+, 6+ ?

?

S2n8.02#

0.78s

Bound and unbound states full reconstruction of the kinematics full reconstruction of the kinematics (p,p’) or (d,p) excitation spectrum (p,p’) or (d,p) excitation spectrum ++Spectroscopic factors

Low-lying spectroscopy of n-rich Kr isotopes

(2p1/2) (1f5/2)

(1g9/2)1

0

50(g7/2)

neutrons Neutron excitation of 96Kr via (p,p’) and shell structure of 97Kr via 96Kr(d,p)


BTD +particle-gamma coupling + Detection at the focal plane for (Z,A) identification

separation of excited states with high-density levelcf LOI-direct ReactionsLOI-direct Reactions Future 4 GASPARD array GAmma Spectroscopy & PArticle Detectionsimulation of exp set-up

PREPARATION OF THE EXPERIMENTAL SET-UP

EXOTICPREPARATION OF THE THEORETICAL FRAMEWORK

Coupled-reaction channel analysis:- treatment of direct reactions for structure embedded in the continuum-proton-nucleus, deuteron-nucleus optical potentials-Microscopic form factors for (p,p’) reactions-Study of benchmark reactionsbenchmark reactions

SP2 Beams : larger incident energies required (cf L window & access to excited states)

CD2target -ray detector exotic beamexotic beam

SPIRAL2SPIRAL2AAZZ

identification

A+1A+1ZZp

beam trackingdevices

particle

detection

LOI “Unbound states”


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. PetracheGANIL: L. Gaudefroy, W. Mittig, F. de Oliveira, P. Roussel-Chomaz, H. Savajols, O. SorlinHMI Berlin, Germany: H.G. Bohlen, Tz. Kokolova, W. Von Oertzen, C. WheldonJINR, FLNR Dubna, Russia: A. Fomichev, M.S. Golovkov , A. Rodin, S. Sidorchuk, S. Stepantsov, G. Ter-Akopian, R. WolskiIKS University of Leuven, Belgium: R. RaabeIPHC Université Louis Pasteur, Strasbourg: Ch. Beck, S. Courtin, A. KhouajaINFN-Catania, Italy: A. MusumarraKVI, Netherlands: M.N. Harakeh, H.G. Wortche Florida State University, US: K.KemperUniversity of Huelva, Spain: I. MartelUniversity of Ioannina, Greece: : T.J. Merzimekis, A. Pakou, D. RoubosUniversity of Santiago de Compostela, Spain: M.D Cortina-GilTheoretical support :CEA-Bruyères-le-Châtel DAM/DIF/SPN: E. Bauge, P. Chau Huu-Tai, J.P. Delaroche, H. Goutte, S.PéruCENBG: M. BenderIPN-Lyon: K. BennaceurIST, Lisboa, Portugal: R. CrespoThe A. Soltan Institute for Nuclear Studies, Hoza, Warsaw, Poland: K. RusekNSCL, MSU, USA: T. DuguetUniversity of Pisa-INFN-Pisa: G. Blanchon, A. BonnacorsoThe Open University, UK: R.S. Mackintosh University of Sevilla, Spain: A.M. Moro VAEC Hanoï, Vietnam: Dao. T. Khoa; INST Hanoï: Hoang S. Than


DO THE BEST POSSIBLE CALCULATIONS !!!!DO THE BEST POSSIBLE CALCULATIONS !!!!DWBA is a limited framework, turns out to be WRONG for strongly-coupled channelscf CRC calculations, CDCC: Nick Keeley’s lecture at ECOLE JOLIOT-CURIE ’07les réactions nucléaires comme sonde de la structure

ANALYSIS OF (D,P) CROSS SECTIONS...

Once upon a time…

Successful analysis for the stable nuclei [cf 40Ca(d,p) ]: E=7, 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 DWBAR. Satchler Direct nuclear reactions, Clarendon Press, Oxford Univ Press 1983

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 …

Ex : N. Timofeyuk & RC Johnson, PRC 59, 1545 (‘ 99) : d break-up included within the adiabatic approach from Johnson & Soper

Analysis of the 16O(d,p)17O,10Be(d,p)11Be, and 11Be(p,d)10Be reactions.

Comprehensive analysis method for (d,p) stripping reactions ; test calc. : 12C(d,p)@ 25 MeV 10Be(d, p) @ 12 and 25 MeV , N. Keeley,* N. Alamanos, and V. L, PRC 69, 064604 (‘04)

« 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. »

MEASURE ELASTIC SCATTERING to estimate coupling effects (virtual coupling potential related to excited states, compound nucleus effects…

needed for coupling scheme … MEASURE INELASTIC SCATTERING (d,d ’) (p,p ’)


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 channelsNEED 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

• Accurate data covering a large angular domain• Elastic : entrance OM potential under control (p,p)• Check role of continuum coupling• Sensitivity to the detailed structure of exotic nuclei,• Test unusual shape +unbound states• Compare to models (SM, HFB, BCS+QRPA, AMD)


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)

Strong pickup-coupling effect on p+11Be elastic scatteringN. Keeley and V. L PRC 77, 014605 (‘08)

CRC calc :11Be(p,d)10Be* pickup to the 5.960 MeV 1- and 6.263 MeV 2- doublet of excited states in 10Be


Drip-line studies

Drip-lines : limit of nuclear binding, large isospinExploration : new structures of exotic nuclei Tests : nuclear modelling & interactions VNN(Tz)

SIMPLE PROBE : (p,p’) combined to Coulex informationdirect reactions in inverse kinematics, missing mass method

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

n , p

local shell change : like N=16 (34, 70..) indicated by Ex(2+), B(E2) S2n, and evolution of neutron excitation

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 chainsMEANS to Probe the structure & spectroscopy at large isospin Measure unbound states

EXPLORATION:


spectroscopy of low-lying states of neutron-rich isotopes via (p,p’), (p,d) (p,t), (d,p)spectroscopy of low-lying states of neutron-rich isotopes via (p,p’), (p,d) (p,t), (d,p)

Measurement to unbound states:Particle-spectroscopyLarge enough intensitiesintensities EURISOLEURISOL

Large angular coverage all reactions measured simultaneously Elastic and transferLow 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 energiesfor (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

Present (1st generation) intensities : few part/sNeeded : (at least) 103-105 /s

34Ne+p @ 25 A.MeV

tt

ppdd

40c.m.

20c.m.

10c.m.

Improvment of exp set-up + Theoretical framework


Theoretical framework for the analysis of direct reactions

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

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 nucleimust be put into question A PRIORI How good (potential, framework) is really good for exotic beams ?How good (potential, framework) is really good for exotic beams ?Validity of optical potentials ? 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

FORMALISM in COUPLEDFORMALISM in COUPLED REACTION CHANNELSREACTION CHANNELS

To include the coupling to excitations AND to reaction channels

COMPLEX MICROSCOPIC POTENTIALSCOMPLEX MICROSCOPIC POTENTIALS

to test the validity of nuclear density

Improved approach (best we can do today)

To be scheduled in 2008 ESNT WorkshopTo be scheduled in 2008 ESNT Workshop STRUCTURE AND REACTIONS IN COUPLED REACTION CHANNELSSTRUCTURE AND REACTIONS IN COUPLED REACTION CHANNELS


Structure and spectroscopy Structure and spectroscopy of exotic nuclei via direct reactionsof exotic nuclei via direct reactions

Conclusions Conclusions PerspectivesPerspectives

Powerful tool for the study of unbound states :DIRECT REACTIONS IN COUPLED CHANNELS

()

Sn

?E (MeV)

Isospindependence

Roleof coupling

to continuum

Beyond mean-fieldrole of many-body

correlationspairing

Effective interaction NN

GOALS

find new aspects de structure weakly-bound exotic nuclei,

new constraints for the nuclear modelsof structure and reaction

modelling of strong interaction in the nucleus for extreme isospin cases

test bench for the unification of the future models for structure and reaction with explicit contribution of the coupling effects

observable

Experimen-talist

theorist

« MOSAÏQUE DES NOYAUX », P. BONCHE, CEA-SPhT

Studies of exotic nuclei need to combine several probes & Require systematics along extended isotopic chains

StructureBound states

Role of the coupling to the

continuum

ReactionsScattering

states

Nuclear Models

PCV

PHYSICS OF THE PUZZLE AND OF THE INTERPLAY


Discussions - Questions

« 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

the force ?the force ?

sp states + Couplings + collective degrees of freedom ?sp states + Couplings + collective degrees of freedom ?

Treatment of the structure embedded in the continuum, of the unbound states ?Extended framework treating on the same footing bound and scattering states ?

« 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. Col`o, 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? Reaction +structure? Revisit scattering theory?


Open questions

Reactions involving states close to continuum ?

STRUCTURE ?

INTERACTION ?

V(r),(r)

NN

Structure theories for states embedded in the continuum ?

We need theories with structure and reaction embedded in the continuum


Conclusions

Ocean of weakly binding energiesOcean of weakly binding energies


Compléments (I)


Structure of exotic nuclei

Experimental explorationExperimental exploration

Rules of the evolution of nuclear structure at large isospin ?

Explore Shell quenchingNuclear structure ?Which interactions ?How to model?

N

ZVNN +VNNN : S. Pieper, Wiringa et al

p

p

nn

T. Otsuka et al

continuum-coupling (CC) effects:K. Bennaceur, M. Ploszajczak, …. A.Volya et al.Density-dependent pairing effects, DFT : T. Duguet et al.

Theoretical challenges: Interplay between these effects

Nuclear potential ; nuclei at larger N/Z weaker binding energy more diffuse nuclear potential (J. Dobaczewski et al. isospin-dependent terms, p-n tensor interaction enhanced nuclear correlations, CC effects change of SO potential (B. Todd-Rutel et al.)


Predictions of the Drip-lines

2 4 6 8 10 12 14

N

16

2

4

6

He

6

Z8

4HeborromeanHe

C

NO

Hn

pp d t8

He

11

Li

F 31

Li

Be14

Be

B

12

19

23

24

RMF

HFB-GognyHFB-Skyrme


Density functional method + Sly4 Skyrme NN interaction

M.V. Stoitsov, et al., PRC68, 054312 (‘03)

microscopic predictions formicroscopic predictions for SS2n2n energy and deformation throughout the mass table energy and deformation throughout the mass table

J. Dobaczewski et al.

Predictions of the drip-lines, HFB-Skyrme

Ni isotopes

Kr isotopes


Reference : calc from PRC[Stoit03]


0+

2+

S2n =7.91

Sn = 4.95

96Kr

6? MeV?

Calc : M.V. Stoitsov, et al., Phys. Rev. C68, 054312 (‘03)Data AME2003

0+

4+

S2n =8.5

Sn = 5.2

94Kr

?

0.67 MeV

1.52

2+

Similar trend forneutron-rich SPIRAL2 beams :few bound states


Predictions of the Drip-lines, HFB-Gogny

M. Girod et al, CEA-DAM


Predictions of the Drip-lines, RMF

125Pd (Z=46) found at RIBF, N=79


Compléments (II)


Nuclear structure explored via elastic and inelastic scattering (p,p’)

0+

2+ (p,p’) probe : sensitive tosensitive to densities, excitation of densities, excitation of

neutrons & protonsneutrons & protons

proton densities & excitation EM probeStable nuclei : (e,e’) probe

Radioactive beams : no direct access to protons but to integrated value B(E2) from Coulex

Weakly bound states ?Continuum coupling ?Isospin dependence ?

Testing ground : weakly-bound light nuclei

Microscopic potential nucleus- nucleon U(rho,E)

drrr Lnpfi

2)( )( Mn, Mp

B(E2;,if)=|Mp|2/(2Ji+1)

Ex : local microscopic complex potential JLM,J.P. Jeukenne, A. Lejeune & C. Mahaux, PRC 16 (‘77) 80 valid for Ep, En up to 160 MeV

n, p

U(,E) = v V (,E) +i w W(,E)

gs

gs

excDENSITIES

tr =<i|(r-r’)|f>exploring…


Search for low-lying resonances and study of neutron excitations

MUST : Y.Blumenfeld et al., NIM A421, 421 (‘99)

CATS : S. Ottini et al., NIM A431, 476 (‘99).

beam

MUST (8 in a wall)

+ CATS

((p,p’) probep,p’) probeParticle spectroscopy

C.Jouanne, VL. et al., 10,11C(p,p’)PRC 72, 014308 (’05)

Nuclear densities, neutron excitation

structure studies by (p,p’) & (p,d) reactions using GANIL/SISSI or SPIRAL beams

and MUST+CATS

Weakly-bound nucleiUnbound excited

stateslow-lying resonances

Inelastic scattering : sensitive to the

shape of the density

Halo, Neutron-skin structure

Elastic scatteringsensitive to the

matter rms

S2n = 0.9750+

2+

6He

1.8 MeV

rmsm (10C) : 2.42 0.1 fm ; rmsm (11C) : 2.33 0.1 fm[rmsm (12C) : 2.30 (3) fm]


PrototypePrototype of (p,p’) & direct reactions at low energy: of (p,p’) & direct reactions at low energy: 88He(p,p’)He(p,p’)

Collaboration : SPhN, GANIL, IPN-Orsay, FLNR-Dubna, Univ. Ioannina (Greece)

PROBE : 8He(p,p’)8He*

MUST

X, Y, T, E

Si Strip 6 x6 cm2

Si Strips 300 m

Si(Li) 3mm

CsI1.5 cm

pp

He

SPIRAL 8He

@ 15.7 A.MeV

14000 /s[1ary beam:

13C @ 75 A.MeV]

CH2 target

Beam detector CATS2

CATS1

test of the validity of the densitieseg 6He(p,p’) @ 40.9 MeV/n GANIL-MUST A. Lagoyannis et al., PLB 518, 27 (‘01)2n-Halo features 6He NPA722, 49c(‘03)

0+

2+

Sn =2.5

S4n =3.1

S2n = 2.1

8He

3.6 MeV?

T1/2 =119 ms

neutron-skin ?Resonances

8He (T1/2= 119ms) I=

104 /s reaction target CH2

set-up at GANILset-up at GANIL

wave fct 8He


Structure of Structure of 88He He

modelsmodels

P. Navratil & W.E. Ormand, PRL88, 152502 (‘02)

V3eff4ħω

ħΩ=13 MeV

B(E2) = 0.25e²fm4

Mn/Mp = 13.5

p n1s1/2

1p3/2

1p1/2

COSMA

SAGAWA

p

n

COSMA: M.V. Zhukov, A.A Korsheninnikov & M.H Smedberg, PRC 50 (‘94) R1H. Sagawa, PLB 286 (‘92) 7

priv. Co.


All direct reactions at the same energy : a need for a complete coupled-channel analysis

Conclusions: structure and spectroscopy of Conclusions: structure and spectroscopy of 88He He (p,p’) (p,d) (p,t) @ 15.7 (p,p’) (p,d) (p,t) @ 15.7 A.MeVA.MeV

8He(p,d)7He transfert 1nResonant states of7HeIndication of a possible 1/2- resonance at low energy PRC73, 044301(’06)

8He(p,p’)E* : 2 states

88HeHe p

77HeHe d

88HeHe2+2+ pl=0l=2

SPIRAL

Coupling to the (p,d) channel to understand the (p,p) PLB 619, 82(’05)

8He(p,d)7He C2S = 4.4 ± 1.3mixing : (p3/2)4 + (p3/2)2 (p1/2)2

2+ 3.62 ± 0.14 0.3 (2)? 5.4 ± 0.5 0.5 (3)

Γ (MeV)E(MeV)

NP A788, 260 (2007)

p n1s1/2

1p3/2

1p1/2

PLB 646, 222(’07)

8He(p,p’) a new resonance

Structure models overestimate Eexc for unbound excited states Understanding of the weakly bound & unbound states requires calculations including the continuum coupling


SPhN - Exotic nuclei Structure and spectroscopy of8He via direct reactions on proton

SPIRAL 8He (T1/2= 119ms)

I= 104 /s ; E=15.7 A.MeV reaction target CH2

wave function 8He

(p,t) fonction d’onde de l’8He % 6He [8He/6He(0+)] =1 ;[8He/6He(2+)] =0.014mélange : (p3/2)4 + (p3/2)2 (p1/2)2

p n1s1/2

1p3/2

1p1/2

Structure de l’état fondamental & recherche d’états 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 réactionsPLB 619. 82 (’05) ; 646, 222 (’07)

NCSM

Calculs en couches sans cœur (NCSM)validés

COSMA:Alpha+4n


Evolution of the neutron skin thickness : ex of Neon isotopes

Density functional.calc. with R. Lombard’s code

Similar trend in HFB-def (Sly4) calc ofJ Dobaczewski, M.V. Stoitsov, et al., PRC68, 054312(‘03)


Neutron-skin structure of 34Ne via direct reactions on proton target

34Ne +p p’ + 34Ne* p + 32Ne + 2n p’ + 34Ne* p + 30Ne + 4n

34Ne(p,p’)34Ne*

20 22 24 26

32Ne

30Ne

34Ne N/Z=2.4 N

31,33Ne unbound

Sn

0+

2+

32Ne

S2n

1.63MeV1.97

S2n0+

2+

34Ne

Sn300keV

947

Searching for low-lying states unbound statesneutron excitations…

Weakly-bound nucleiSmall Sn, S2n

probe the structure & spectroscopy at large isospin measure unbound states detection devices

Documents

structure spectroscopy

neutronskin structure

structure of exotic

evolution of nuclear

shell structure dripline

neutron excitation

dripline nuclei

particles p