PION ABSORPTION AT REST IN HE-4

摘要

The emission of nn, np-, nd- and nt-pairs following pi(-)-capture in gaseous He-4 has been studied in a coincidence experiment. Quasifree 2N-absorption is the dominant absorption mechanism with a ratio of r = 4.0(-1.5)(+0.8) for absorption on a nucleon pair with isospin I = 0 and I = 1. Also collinear processes involving more than two nucleons have been observed, including NN final-state interaction with small relative momenta as well as emission of deuterons and tritons. Upper limits are given for phase-space-distributed, i.e. non-collinear 3N- and nnd-emission. [References: 38]