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

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

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

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

5. Strategy … “ Fast ” nucleon (proton) removal   ℓ (n) = 0 * IFF proj. structure known  deduce structure of A-1 system (core -1  valence nucleon)  Proton removal (S p ~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  ℓ n = 0  frag. recoil induced by proton removal  scattering of valence neutron VALIDATE approach using 11 Be beam (S n = 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 10 He, 11 Li

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

8. Experimental Approach Fast nucleon removal from projectile with known structure + inflight decay of unbound system VfVf VnVn V f -V n target Proj. A Z  A-1 Z + n

9. Resolution Experimental Response Function Efficiency FWHM ~ 0.3 E d 1/2 nnnn JL Lecouey LPCC 02-03 JL Lecouey LPCC 02-03 model distributions must be “ filtered ” through the simulation model distributions must be “ filtered ” through the simulation

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

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

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

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

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

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

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

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

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

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

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

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

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

23. Conclusions & Perspectives 11 Be proton knockout suggests that selection rule valid  spectroscopy possible beyond the dripline using knockout from RNB …  10 Li : low-lying s-wave strength (a s = -14±2 fm) low-lying p-wave resonance (E r = 0.5 MeV)  N= 7 inversion confirmed [ but …  p 3/2  s 1/2, p 1/2, d 5/2 ?? ]  9 He : low-lying s-wave strength (a s  0 fm) + E x  1.2 MeV (l>0)  N= 7 inversion … ? [ FSI 0)  N= 7 inversion … ? [ FSI << 9 Li+n ?? ]  EXPT: higher resolution & statistics; improved neutron detection & I B

24. Conclusions & Perspectives  validity/character of s-wave virtual states ?? eg., deformed 9 Li & 12 Be 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 ?)  validity/character of s-wave virtual states ?? eg., deformed 9 Li & 12 Be 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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