Diffraction dissociation and Coulomb dissociation of high-energy neutrons by nuclei

Abstract

We present the results of a spark chamber experiment in which we studied the reaction n + A → (p + π −) + A′, where the (p π −) pair is coherently produced off carbon, copper, and lead nuclei. Between 5 000 and 55 000 good events were collected with each target. Incident neutrons in the momentum range 10 to 28 GeV/ c were used. Forward-going (p π −) pairs from the above reaction were detected in a wire spark chamber spectrometer which measured the momentum and angles of each particle. The observation of a sharp forward peak (of width appropriate to the nuclear radius) indicated that a large fraction of the events were coherently produced. There is no evidence for any appreciable production of the well-established I = 1 2 nucleon isobars; our limits appear to be inconsistent with estimates based on a straightforward extrapolation of pp data. The lead data show evidence for coulomb production of the Δ (1236). The carbon data indicate a spin J ⩾ 3 2 for the coherently produced (p π −) states with pure J = 3 2 possible. We cannot draw any firm conclusions about helicity conservation. The Drell-Hiida-Deck model does not adequately fit the data, nor is the double-Regge-pole model completely satisfactory.