A 71 Ga(3 He, t) 71 Ge charge-exchange experiment was performed to extract with high precision the Gamow-Teller (GT) transition strengths to the three lowest-lying states in 71 Ge, i.e., the ground state (1/2 −), the 175 keV (5/2 −) and the 500 keV (3/2 −) excited states. These are the relevant states, which are populated via a charged-current reaction induced by neutrinos from reactor-produced 51 Cr and 37 Ar sources. A precise measurement of the GT transition strengths is an important input into the calibration of the SAGE and GALLEX solar neutrino detectors and addresses a long-standing discrepancy between the measured and evaluated capture rates from the 51 Cr and 37 Ar neutrino calibration sources, which has recently spawned new ideas about unconventional neutrino properties.

The very neutron-rich oxygen isotopes 25

Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R^{3}B/LAND setup with incident beam energies in the range of 300-450  MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type ^{A}O(p,2p)^{A-1}N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.

The elusive β − p + decay was observed in 11 Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber (pAT-TPC) in an experiment performed at ISAC-TRIUMF. The measured β − p + branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in 11 B above the proton separation energy.

We report the measurement of reaction cross sections (σ ex R ) of 27,29 F with a carbon target at RIKEN. The unexpectedly large σ ex R and derived matter radius identify 29 F as the heaviest twoneutron Borromean halo to date. The halo is attributed to neutrons occupying the 2p 3/2 orbital, thereby vanishing the shell closure associated with the neutron number N = 20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of 27 F but are challenged for 29 F.