Measurements of the differential cross section of the reactionpp→dπ+from 3.0 to 5.0GeVc

Abstract

A measurement of the complete differential cross section for the reaction $\mathrm{pp}\to d{\pi }^{+}$ at 3.00, 3.20, 3.43, 3.65, 3.83, 4.00, 4.20, and 5.05 $\frac{\mathrm{GeV}}{c}$ incident proton momentum has been made in an attempt to establish the role of the $\Delta$ (1950) in this region. The data show that the previously observed enhancement in the forward cross section between 3 and 4 $\frac{\mathrm{GeV}}{c}$ due to this isobar is an effect which damps out quickly as the production angle departs from zero degrees, in contrast with the well-known enhancement at 1.35 $\frac{\mathrm{GeV}}{c}$, which is evident at all angles. In particular, the one-pion-exchange model is in poor agreement with the extended set of data. A detailed description is given of a novel proportional-wire-chamber system which facilitated the selection of this rather rare reaction from a very high competing background.