We determine the value of the ω − ρ − π mesons coupling (g ωρπ ), in the context of the vector meson dominance model, from radiative decays, the ω → 3π decay width and the e + e − → 3π cross section. For the last two observables we consider the effect of either a heavier resonance (ρ ′ (1450)) or a contact term. A weighted average of the results from the set of observables yields g ωρπ = 14.7 ± 0.1 GeV −1 in absence of those contributions, and g ωρπ = 11.9 ± 0.2 GeV −1 or g ωρπ = 11.7 ± 0.1 GeV −1 when including the ρ ′ or contact term respectively. The inclusion of these additional terms makes the estimates from the different observables to lay in a more reduced range.Improved measurements of these observables and the ρ ′ (1450) meson parameters are needed to give a definite answer on the pertinence of the inclusion of this last one in the considered processes.

No abstract

The inclusion of the unstable features of a spin-1 particle, without breaking the electromagnetic gauge invariance, can be properly accomplished by including higher order contributions as done in the so-called fermion loop scheme (for the W gauge boson), and the boson loop scheme (for vector mesons). This induces a non trivial modification to the electromagnetic vertex of the particle, which must be considered in addition to any other contribution computed as stable particles. Considering the modified electromagnetic vertex, we obtain general expressions for the corresponding corrections to the multipoles as a function of the mass of the particles in the loop. For the W gauge boson no substantial deviations from the stable case is observed. For the ρ and K * mesons the mass of the particles in the loop makes a significant effect, and can be comparable with corrections of different nature .

We determine the magnetic dipole moment of the rho meson using preliminary data from the BaBar Collaboration for the e+e- → π+π-2π0 process, in the center of mass energy range from 0.9 to 2.2 GeV. We describe the γ* → 4π vertex using a vector meson dominance model, including all intermediate resonance contributions. We find that μρ = 2.1 ± 0.5 [e/2mρ].

We determine the magnetic dipole moment of the rho meson using preliminary data from the BaBar Collaboration for the e + e − → π + π − 2π 0 process, in the center of mass energy range from 0.9 to 2.2 GeV. We describe the γ * → 4π vertex using a vector meson dominance model, including the intermediate resonance contributions relevant at these energies. We find that µ ρ = 2.1 ± 0.5 in e/2m ρ units.