Flavor SU(3) Symmetry of the Pseudoscalar Meson-Baryon Couplings in QCD sum rules.

por Makoto Oka (Tokyo Institute of Technology)

martes 31 oct. 2000 12:30 → 13:30 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

It is important to study the meson-baryon couplings carefully as they are the key quantities that determine the meson exchange interactions between baryons. The SU(3) symmetry plays a central role there, but its foundation is not solid from QCD viewpoints. We have evaluated the diagonal meson-baryon couplings, $\pi NN$, $\eta NN$, $\pi \Xi\Xi$, $\eta \Xi\Xi$, $\pi\Sigma \Sigma$ and $\eta \Sigma \Sigma$, using the QCD sum rules for the baryon-baryon correlation function with a meson, $i \int d^4x e^{iqx} \langle 0|{\rm T}[J_B(x) \bar J_B(0)] |M(p)\rangle$. We compare three Dirac structures: $i\gamma_5$, $i\gamma_5 \gamma\cdot p$, and $\gamma_5\sigma_{\mu\nu}q^\mu p^\nu$ structures and have found that the last one gives the most reliable predictions. We consider general combinations of two independent baryon interpolating fields and study how the results depend on the interpolating fields. In the SU(3) limit, we identify the OPE terms responsible for the $F/D$ ratio, and find the ratio $F/D \sim 0.68$, which is surprisingly close to the value predicted by the SU(6) symmetry. SU(3) breaking effects are partially taken into account to see their significance.