Abstract
The nucleus was populated from a beam impinging on a Be target with an energy of . The internal decay via -ray emission of the metastable state was observed. As the structure of this isomeric state has to involve at least four unpaired nucleons, it cannot be populated in a simple two-neutron removal reaction from the ground state. The isomeric state was produced in the low-momentum (-energy) tail of the parallel momentum (energy) distribution of , suggesting that it was populated via the decay of the resonance into a proton. This process allows the population of four-nucleon states, such as the observed isomer. Therefore, it is concluded that the observation of this metastable state in is a consequence of the quark structure of the nucleons.
- Received 2 June 2016
DOI:https://doi.org/10.1103/PhysRevLett.117.222302
© 2016 American Physical Society