Axial-vector mesons in a relativistic point-form approach

The Poincaré invariant coupled-channel formalism for two-particle systems interacting via one-particle exchange, which has been developed and applied to vector mesons, is now applied to axial vector mesons. We thereby extend the previous study of a dynamical treatment of the Goldstone-boson exchange by comparison with the commonly used instantaneous approximation to the case of orbital angular momentum $l=1$. Effects in the mass shifts show more variations than for the vector-meson case. Results for the decay widths are sizable, but comparison with sparse experimental data is inconclusive.

Figure 1

Results for axial-vector meson spectra: Experimental data with uncertainties (particle name), oscillator (O), CC with vertex form factor (Cf), CC with FF=1 (C1), instantaneous approximation with vertex FF (If), and IA with FF=1 (I1).