Ab initio calculations available now (e.g. FMD: PVIX, HK 6.8)

Structure of few-nucleon systems near and beyond the driplineHaik SimonGesellschaft für Schwerionenforschung / Darmstadt • Ab initio calculations available now (e.g. FMD: PVIX, HK 6.8) • (Two) particle correlations vs. mean field • Shell model evolution (residual interactions) • How to measure that ?

Shell evolution ( N = 7 ) L. Chen, et al. , PLB505(2001)21 I. Talmi, I. Unna, PRL4 (1960) 469 P.G. Hansen, NUPA682 (2001) 310c

Gamov-Teller b-decay ISOLDE/CERN 3/2- 11Li b- b = 6.3(6) % 504 keV 320 keV 1/2- E1 1/2+ 11Be  11Lig.s.: (1s1/2)2 /(0p1/2)2  1 M.J.G Borge et al. PRC55(1997)R8

2n transfer reaction JINR/DUBNA • 6He is clustered • i.e. a+ n + n • Dominantly • in di-neutron • configuration G.M. Ter-Akopian et al., PLB 426 (1998) 251

Region of Interest: near and beyond the dripline Vnn Vcn Vcn

Example: Reaction mechanism for two-neutron halo break-up • vbeam  0.7 – 0.9 c • Neutron multiplicity final state • Choice of target Knock-out ( 1n ) Nuclear excitation ( 2n ) Coulomb excitation ( 2n )

Experimental Setup

Experimental Method Problem: reconstruct 3 body system from 2 body final state ! • Correlations from the ‚missing‘ particle • momentum • angular • invariant mass of the subsystem(s) • Remaining structure • core polarization

Angular correlation 6He p5He = -pn1 W(nf) = 1 + Acos2 nf nf a A = 1.50 (3)  6Heg.s: (0p1/2)2  7%. n2 d/ dcos (nf ) 5He* n2 n1 A=3 a 6Heg.s cos (nf) L.Chulkov, G.Schrieder ZPA359(1997)231

Valence neutron momentum distribution for the two-neutron halo nucleus 11Li Neutron momentum distribution 9Li 10Li n2 n1 H.S. et al. PRL83 (1999) 496

Angular correlation 11Li Interference (s- and p- shell) S=0 :  cos nf W(nf) = 1 – 1.03(4) cos nf+ 1.41(8) cos2 nf  H.S. et al. PRL83 (1999) 496

Conclusion 11Li • 11Li properties are reflected in the population of states in 10Li* following the knockout reaction. • Consistent picture in different observables. • Continuum spectroscopy of an unbound system 10Li*. M. Meister, H.S., et al., in preparation

Experimental Method Problem: characterize a three body final state in the continuum ! • Test model assumption • test deduced observable (e.g. sum rule) • Measure ‚directly‘  how to measure a three body correlation ?

Coulomb break-up 6He Ex  10 MeV 100%cluster sumrule  B(E1) = 1.37 e2fm2 B.V. Danilin et al., NUPA632 (1998) 383 ra-nn = 3.4(4) fm dnn = 4.0(4) fm rHalo = 3.0(3) fm P. Egelhof et al., EPJA15(2002)27 T. Aumann et al., PRC59(1999)1252

Three body continuum pf-nn q pnn • Reduction of coordinates • 9 variables  6 variables  5 variables  2 variables ( e, q ) • c.m. E* rot. inv. • e is the fraction of total energy in a subsystem (e.g. e = Enn/Ennf) • q is the angle between the relative momenta (e.g. pnn, pf-nn) • Three body correlation function (expansion in hyperspherical harm.): • Complex coefficients C depend on quantum numbers a={K,L,S,lx,ly}

Coulomb break-up 6He B.V. Danilin et al., NUPA632 (1998) 383 2n 5He L.V. Chulkov, H.S., I.Thompson, et al., in preparation

Beyond the dripline: 5H C(6He,t+n+n) M. Meister et al., PRL91(2003)162504

Summary / Outlook … Supported by BMBF and GSI • Reaction Mechanism • is understood • different processes can be separated experimentally • Nuclear Structure • evolution of shell structure towards the drip lines • residual interaction: clusters, pairing important • Perspectives • excitation modes of exotic nuclei • extreme states of nuclear matter (4n, 7H, …) Thanks to all my collaborators of the FRS/ALADIN-LAND experiments !

Large Area Neutron Detector Efficiency 1 Resolution:sTof ~ 200 pssp ~ 5 - 10 MeV/csIVM ~ 0.1 - 1. MeV Nucl. Instr. Meth. A314 (1992) 136 Neutron Energy (MeV)

Ab initio calculations available now (e.g. FMD: PVIX, HK 6.8)