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Abstract: Two complementary experimental techniques have been used to extract precise branching ratios to unbound states in 12C from 12N and 12B β-decays. In the first the three α-particles emitted after β-decay are measured in coincidence in separate detectors, while in the second method 12N and 12B are implanted in a detector and the summed energy of the three α-particles is measured directly. For the narrow states at 7.654 MeV () and 12.71 MeV () the resulting branching ratios are both smaller than previous measurements by a factor of ≃2. The experimental results are compared to no-core shell model calculations with realistic interactions from chiral perturbation theory, and inclusion of three-nucleon forces is found to give improved agreement. [Copyright &y& Elsevier]

In this Letter we develop an analytical model in order to study electromagnetic processes involving loosely bound neutron-rich and proton-rich nuclei. We construct a model wave function, to describe loosely bound few-body systems, having the correct behaviour both at large and small distances. The continuum states are approximated by regular Coulomb functions. As a test case we consider the two-body Coulomb dissociation of 8B and, the inverse, radiative capture reaction. The difference between using a pure two-body model and the results obtained when incorporating many-body effects, is investigated. We conclude that the interpretation of experimental data is highly model dependent and stress the importance of measuring few-body channels. [Copyright &y& Elsevier]

Abstract: The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+)+n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies. [Copyright &y& Elsevier]

The 7Be fragments produced in one-proton removal from relativistic 8B nuclei of 936 MeV/nucleon in a carbon target have been detected in coincidence with γ rays emitted by these fragments at the reaction target. It is found that 13±3% of the 7Be fragments are released in the 429 keV excited state, 7Be*, which gives direct experimental information on the ground state configuration of 8B. The longitudinal momentum distributions (p∥) of the 7Be fragments have been measured, both inclusively and in coincidence with de-excitation γ-rays from 7Be*. The widths and cross sections of the respective p∥ distributions are compared with calculations in a three-body cluster model. [Copyright &y& Elsevier]