Structure of Nuclei Beyond the Dripline

1. Structure of Nuclei Beyond the Dripline Collaboration LPC-CHARISSA-DEMON H Al Falou, JL Lecouey, F Carstoiu, FM Marqués,NAO …

2. Structure Beyond the Neutron Dripline via Intermediate-Energy “Knockout”& Breakup • Introduction • Experimental • Approach • “Selection Rules”, • Backgrounds, … N=7 : 10Li & 9He Conclusions & Perspectives

3. The Light Neutron-Rich Nuclei … 10Li Structure =core+xn 9He … driplines and beyond experimentally accessible, extreme test of models (shell model, shell model in continuum, “ab initio”, cluster, etc) LPC Programme: H Al Falou LPCC 07-03,G Normand LPCC 04-03, JL Lecouey LPCC 02-03

4. Particle Stable Nuclei – “Knockout”/Nucleon Removal 43-68 MeV/nucleon 1-600 pps s-1n ~ 50 - 200 mb FWHM ~ 50 - 240 MeV/c Inclusive : E Sauvan, et al., PLB 2000 ; PRC (2004)

5. Strategy … “Fast” nucleon (proton) removal  Dℓ(n) = 0 *IFF proj. structure known  deduce structure of A-1 system (core-1 valence nucleon)  Proton removal (Sp~15 MeV) from very neutron-rich beams  systems beyond dripline – observe frag.+ n FSI* M Zinser et al., PRL 75 (1995) 1719 L Chen et al. PLB 505 (2001) 21

6. Issues : ReactionStructure… • Projectile weakly bound valence neutron  relaxation of Dℓn = 0  frag. recoil induced by proton removal  scattering of valence neutronVALIDATE approach using 11Be beam (Sn = 0.5 MeV) In parallel explore evolution of N=7 g.s. parity inversion  test of structure models & input for for 3-body modelling of 10He, 11Li

7. N=7 1/2+ – 1/2- Level Inversion … PG Hansen et al. … 10Li &9He ??

8. Vf Vf-Vn Vn Proj. target AZA-1Z + n Experimental Approach Fast nucleon removal from projectile with known structure+ inflight decay of unbound system

9. Resolution Efficiency Experimental Response Function FWHM ~ 0.3 Ed1/2 en model distributions must be “filtered” through the simulation JL Lecouey LPCC 02-03

10. (Approx.) Selection Rules … • 1 & 2-proton knockout  Dℓn=0 proj. valence neutron config.C(11Be,10Li)X ,C(11Be,9He)X s1/2 [ 11Be C2S (s1/2) 0.8 ]well adapted to probing low-lying s-wave strength(ii) fragmentation (-xp,-xn)  population via neutron-decay of N+1 system C(14B,10Li)X , C(14B,9He)X  s1/2 + p1/2 + …CAVEAT*: decay of narrow resonances in N+1,2,… systemsNote - Edlineshape dependent on initial state (esp. for broad final states) *EXAMPLE: C(15B,12Be+n) via 14Be*(2+)

11. BACKGROUND: C(17C,15B+n)X – single-proton knockout Er = 85  15 keV Gsp << 100 keV  uncorrelated 15B+n distribution “background” ≡ non-resonant continuum  event-mixed distribution ** ie., uncorrelated fragment-neutron pairs JL Lecouey et al, PLB672 (2009 6JL Lecouey, Few-Body Systems 34 (2004) 21

12. BACKGROUND : C(14B,6He+n)X – fragmentation “background”≡ sequential neutron decay/evaporation from PLF + continuum JL Lecouey, LPCC T 02-03.

13. Scattering/Virtual s-wave States as = 0 fm no FSI ; as << 0 fm stronger FSI Note -final lineshape Ed(frag+n) depends on projectile

14. 10Li : Low-Lying Level Scheme * *“Partial” – also d(9Li,p) ; new LAND-GSI etc Theory: also MCSM Otsuka et al, … s-virtual Er ~ ћ2 / 2as

15. 10Li : C(11Be,9Li+n) @ 35 MeV/nucleon [-1p] uncorrelated / event-mixed distribution * * normalised for comparison at high Ed H Al Falou LPCC 07-03

16. 10Li : C(11Be,9Li+n) @ 35 MeV/nucleon [-1p] s-wave [as = -17±2 fm] + non-resonant continuum H Al Falou LPCC 07-03

17. 10Li : C(14B,9Li+n) @ 35 MeV/nucleon [-2p,-2n] s-wave [as = -10 ±2 fm] + p-wave [Er = 0.51, G0= 0.54 MeV] + background [ Decay of 11Li* & 12Li … ? ] H Al Falou LPCC 07-03

18. 9He : Low-Lying Level Scheme * ( ) ( ) ( ) *AlsoIAS expts ; MUST (d,p) under analysis ; LAND-GSI Theory: also MCSM Otsuka et al., …

19. 9He : C(11Be,8He+n) @ 35 MeV/nucleon [-1p] uncorrelated distribution/event mixed distribution H Al Falou LPCC 07-03

20. 9He : C(11Be,8He+n) @ 35 MeV/nucleon [-1p] s-wave [as = -3 ~ 0 fm (3s)] + non-resonant continuum H Al Falou LPCC 07-03

21. 9He : C(14B,8He+n) @ 35 MeV/nucleon [-3p,-2n] uncorrelated distribution/event mixed distribution H Al Falou LPCC 07-03

22. 9He : C(14B,8He+n) @ 35 MeV/nucleon [-3p,-2n] s-wave [as= -3 ~ 0 fm] + p-wave [Er = 1.2, G0= 1.0 MeV] + background [ Decay of 10He & 11He … ? ] H Al Falou LPCC 07-03

23. Conclusions & Perspectives • 11Be proton knockout suggests that selection rule valid spectroscopy possible beyond the dripline using knockout from RNB …10Li : low-lying s-wave strength (as = -14±2 fm) low-lying p-wave resonance (Er = 0.5 MeV)  N= 7 inversion confirmed[ but … pp3/2ns1/2 ,np1/2 ,nd5/2 ?? ] 9He : low-lying s-wave strength (as  0 fm) + Ex1.2 MeV (l>0) N= 7 inversion … ?[ FSI << 9Li+n ?? ]EXPT:higher resolution & statistics; improved neutron detection & IB

24. Conclusions & Perspectives validity/character of s-wave virtual states ?? eg., deformed 9Li & 12Be cores  realistic structure + reaction modelling needed (lineshape and cross section) including non-resonant continuum + other backgrounds …first step – estimate frag. recoil effectsvalence neutron scattering (approx. free neutron scattering ?)

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