Radiative transition processes of light vector resonances in a chiral framework

Abstract

Within the framework of chiral effective field theory, we study various electromagnetic processes with light vector resonances: $K^{\ast }(892)\to K\gamma$, $e^{+}{e}^{-}\to K^{\ast }(892)K$ and the $\omega \pi {\gamma }^{\ast }$ form factors. With two multiplets of vector resonances being introduced, we fit the decay widths of $K^{\ast 0}\to K^0\gamma$, $K^{\ast +}\to K^{+}\gamma$, and the pertinent measurements from the $e^{+}{e}^{-}\to K^{\ast \pm }(892)K^{\mp }$ cross sections, such as moduli and relative phases between the isoscalar and isovector components from BABAR collaboration, together with the $\omega \pi$ form factors from NA60, SND and CLEO collaborations. The values of resonance couplings, masses and widths of the excited vector states ${\rho }^{\prime }$ and ${\varphi }^{\prime }$ are then determined. The ${\omega }^{\prime }$-${\varphi }^{\prime }$ mixing angle is discussed and turns out to be quite different from the ideal mixing case. Three sources of $SU(3)$ symmetry breaking effects in the $\Gamma (K^{\ast }\to K\gamma )$ decays are identified and analyzed in detail.

Comments: 27 pages, 5 figures. To match the published version. Title is slightly changed. The mass splitting operators for the vector resonances are introduced. Revised fits and discussions are presented with these new terms