ISSN - 03702693, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 1999, vol. 458, p. 190-196
Higher partial waves in pp → ppη near threshold
Exclusive measurements of the production of η-mesons in the pp → ppη reaction have been carried out at excess energies of 16 and 37 MeV above threshold. The deviations from phase space are dominated by the proton-proton final state interaction and this influences particularly the energy distribution of the η-meson. However, evidence is also presented at the higher energy for the existence of an anisotropy in the angular distributions of the η-meson and also of the final proton-proton pair, probably to be associated with D-waves in this system interfering with the dominant S-wave term. The sign of the η angular anisotropy suggests that ρ-exchange is important for this reaction. © 1999 Published by Elsevier Science B.V. All rights reserved.