Collaboration LPC-CHARISSA-DEMON H Al Falou, FM Marqués, JL Lecouey, NA Orr, … Spectroscopy Beyond the Neutron Dripline: 9 He & 10 Li

“ I have come 500 miles just to see a halo … ” Who wrote and sang …

MotivationExperimentalApproach Selection “Rules” Backgrounds N=7 : 10 Li & 9 He N=7 : 10 Li & 9 He Conclusions Conclusions Spectroscopy Beyond the Neutron Dripline: 9 He & 10 Li

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

Light Unbound Neutron-Rich Systems input for 3-body models input for 3-body models 3-body systems  n-n and core-n interactions 11 Li : 9 Li-n interaction  spectroscopy of 10 Li 10 He : 8 He-n interaction  spectroscopy of 9 He

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

Experimental Approach … “knockout” or breakup + inflight decay projectile structure known VfVf VnVn V f -V n target Proj. A Z  A-1 Z + n

DEMON 90 modules ( NE213 )  ToF & position  n ~ 10% Kinematically “Complete” Measurement

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

Selection “Rules” - Sudden Approximation (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 ] (ii) fragmentation (-xp,-xn)  valence neutron config. + others C( 14 B, 10 Li)X, C( 14 B, 9 He)X  s 1/2 + p 1/2 + … C( 12 Be, 9 He)X  s 1/2 + p 1/2 + d 5/2 + … NB: E d lineshape dependent on initial state (esp. for broad final states)

“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, nucl-ex/ JL Lecouey et al, nucl-ex/

“background” ≡ neutrons evaporated from PLF + continuum BACKGROUND : C( 14 B, 6 He+n)X – fragmentation JL Lecouey, LPCC T JL Lecouey, LPCC T

Scattering/Virtual s-wave States a s = 0 fm no FSI ; a s << 0 fm stronger FSI

10 Li : Low-Lying Level Scheme * * “ Partial ” – also d( 9 Li,p) etc s- virtual E r ~ ћ 2 / 2a s

10 Li : C( 11 Be, 9 35 MeV/nucleon H Al Falou LPCC uncorrelated / event-mixed distribution * * normalised for comparison at high E d

10 Li : C( 11 Be, 9 35 MeV/nucleon s-wave [a s = -14±2 fm] + non-resonant continuum H Al Falou LPCC 07-03

10 Li : C( 14 B, 9 35 MeV/nucleon s-wave virtual state + p-wave [E r = 0.51,    = 0.50 MeV] + background H Al Falou LPCC 07-03

9 He : Low-Lying Level Scheme * * 9 Li IAS expts not shown ; [Set87, Boh88, Oer95] assignments tentative

9 He : C( 11 Be, 8 35 MeV/nucleon uncorrelated distribution/event mixed distribution H Al Falou LPCC 07-03

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

9 He : C( 14 B, 8 35 MeV/nucleon uncorrelated distribution/event mixed distribution H Al Falou LPCC 07-03

9 He : C( 14 B, 8 35 MeV/nucleon s-wave [a s = -3 ~ 0 fm] + p-wave [E r = 1.2,    = 1.0 MeV] + background H Al Falou LPCC 07-03

9 He : C( 12 Be, 8 41 MeV/nucleon s-wave [a s = -10 fm] + p 1/2 [E r = 1.2 MeV] + (d 5/2 ) [E r = 2.4 MeV] + background G Normand LPCC 04-03

Conclusions & Perspectives spectroscopy beyond the dripline using breakup/knockout of 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 & 2.4 MeV (l>0)  N= 7 inversion … ?? [ FSI 0)  N= 7 inversion … ?? [ FSI << 9 Li+n ?? ]  validity of s-wave virtual states (eg., deformed 9 Li core) ??  more realistic structure + reaction modelling needed … … including non-resonant continuum + other backgrounds