Quasifree Δ production in hadron-nucleus reactions

Abstract

We have measured the quasifree Δ production in proton-nucleus reactions at 4 GeV/ c, for the first time, detecting both scattered protons and decay products of the Δ. The peak location in the momentum spectra of scattered protons was consistent with the Δ excitation if the binding effect was taken into account. The peak shift toward lower excitations observed in inclusive measurements of ( 3He, t) and (p, n) reactions was not found in our semi-exclusive measurements. In order to solve this puzzle, it is essential to carry out both inclusive and coincident measurements in the same reaction.