The contribution of the $a_1(1260)$ meson to the amplitudes of the decays $\rho (770)\to 4\pi$, $\omega (782)\to 5\pi$, and $\varphi (1020)\to 5\pi$ is analyzed in the chiral model of pseudoscalar, vector, and axial vector mesons based on the generalized hidden local symmetry added with the anomalous terms. The analysis shows that inclusion of $a_1$ meson in the intermediate states results in enhancement of the branching ratios of the above decays by the factor ranging from 1.3 to 1.9 depending on the mass of $a_1$ meson ranging from 1.23 GeV to $m_{a_1}=m_{\rho }\sqrt{2}=1.09\mathrm{G}\mathrm{e}\mathrm{V}$, the greater factor standing in case of lower mass of the $a_1$.

• Received 7 December 2004

DOI:https://doi.org/10.1103/PhysRevD.71.034015