Experimental evidence for the ⁸B ground state configuration

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