arXiv subjects
Publications and source records attributed to C. R. Munz.
We show that instanton effects may play a crucial role in the decay of scalar mesons into two pseudoscalars. Particularly the branching ratios of two meson decays of the $f_0(1500)$, which is considered as a glue-ball candidate, are then compatible with an ordinary $q \bar{q}$-structure of this resonance and a small positive SU(3) mixing angle, close to a result recently calculated with the same instanton-induced force.
We present a relativistic calculation of two-photon decays for heavy and light mesons in the framework of the Salpeter equation for quark-antiquark states. The meson-photon-photon vertex is computed by reconstructing the Bethe-Salpeter vertex function and evaluating the four-dimensional Feynman diagram with off-shell quark amplitudes. The two-photon width for light and heavy quarkonia up to spin equal six are calculated with different parameter sets taken from the literature thus giving a complete overview on the mesonic two-photon physics. We find that relativistic effects including the negative energy components of the wave function are important for any two-photon width - even for heavy quarkonia - yielding a remarkable agreement with available data.
The electromagnetic form factor for the $K^0$ is calculated in a covariant formulation of the Salpeter equation for $q\bar q$ - bound states, which has been presented recently for the mass spectrum, decay properties and form factors of the light pseudoscalar and vector mesons. The $K^0$ charge radius dependence on the difference between strange and down constituent quark mass is discussed.
In a relativistic quark model with linear confinement and an instanton-induced interaction which solves the $η$-$η'$ puzzle, scalar mesons are found as almost pure SU(3) flavor states. This suggests a new interpretation of the scalar nonet: We propose that the recently discovered $f_0(1500)$ is not a glueball but the scalar (mainly)--octet meson for which the $K\bar{K}$ decay mode is suppressed. The mainly--singlet state is tentatively identified with the $f_0(980)$. The isovector and isodoublet states correspond to the $a_0(1450)$ and $K^{\ast}(1430)$, respectively.