Photoproduction of {\omega} Mesons off the Proton

The differential cross sections and unpolarized spin-density matrix elements for the reaction gamma rho -> rho omega were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5GeV. These observables were measured from the radiative decay of the omega meson, omega -> pi(0)gamma. The cross sections cover the full angular range and show the full extent of the t-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, abeam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn-Gatchina partial wave analysis (PWA). The dominant contribution to omega photoproduction near threshold was found to be the 3/2(+) partial wave, which is primarily due to the sub-threshold N(1720)3/2(+) resonance. At higher energies, pomeron-exchange was found to dominate whereas pi-exchange remained small. These t-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the 1/2(,)(-) 3/2(-), and 5/2(+) partial waves were also found to contribute significantly. (C) 2015 The Authors. Published by Elsevier B.V.