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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

Calén H., Dyring J., Fäldt G., Fransson K., Gustafsson L., Häggström S., Höistad B., Johanson J., Johansson A., Johansson T., Kullander S., Mörtsell A., Ruber R., Złomańczuk J., Ekström C., Kilian K., Oelert W., Sefzick T., Bilger R., Brodowski W., Clement H., Wagner G. J., Bondar A., Kuzmin A., Shwartz B., Sidorov V., Sukhanov A., Dunin V., Morosov B., Povtorejko A., Sukhanov A., Zernov A., Kupsc A., Marciniewski P., Stepaniak J., Zabierowski J., Turowiecki A., Wilhelmi Z., Wilkin C.

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.