科研之友
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摘要
Associative photoproduction of omega meson and N-*(1440) on nucleons, gamma+N-->omega+N-*(1440), in the near threshold region is investigated in a framework employing effective Lagrangians. Besides pi exchange in the t channel, baryon exchanges, i.e., N and N-* exchanges, in the s and u channels are also taken into account in calculations of differential cross section and beam asymmetry. Important inputs of this model are the vector and tensor coupling constants of omegaNN(*)(1440) vertex, which are assumed to be equal to the values of these couplings for omegaNN vertex. Using our previous estimation of omegaNN coupling constants obtained from a fit to available experimental data on photoproduction of omega meson in the near threshold region, we produce the necessary numerical predictions for different observables in gamma+N-->omega+N-*(1440). Numerical results show that at low parallel totparallel to dominant contribution comes from t channel pi exchange while the effects of nucleon and N-*(1440) pole terms can be seen at large parallel totparallel to. Our predictions for the differential cross section and beam asymmetry for the processes gamma+N-->omega+N-*(1440), where N is proton and neutron, at E-gamma=2.5 GeV are presented with zero width approximation and also with the inclusion of width effects of N-*(1440).
