Neutron spectra at 0° from proton-proton collisions between 647 and 805 MeV

Abstract

Momentum spectra of neutrons at 0° from the process $\mathrm{pp}\to \mathrm{np}{\pi }^{+}$ have been measured at 647, 771, and 805 MeV. Absolute cross sections $\frac{d^2\sigma }{d\Omega \mathrm{dp}}$ and $\frac{d\sigma }{d{\Omega }^{*}}$ are given for all three energies. A phenomenological calculation using only $S$- and $P$-wave $\pi N$ phase shifts and an $NN$ final-state interaction appears to account for the shapes and magnitudes of the spectra quite well. Comparison with the process $\mathrm{np}\to pX$ indicates a non-negligible contribution from nonresonant amplitudes.