The F/D ratio and meson-baryon couplings from QCD sum rules-II

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Using QCD sum rules, we compute the diagonal meson-baryon couplings, πNN, ηNN, πΞΞ, ηΞΞ, πΣΣ and ηΣΣ, from the baryon-baryon correlation function with a meson, i∫ d⁴x eiq· x < 0| T JB(x) JB(0)|M(p)>. The calculations are performed to leading order in pμ by considering the two separate Dirac structures, i γ₅ γμpμ and γ₅ σμν qμpν separately. We first improve the previous sum rule calculations on these Dirac structures for the πNN coupling by including three-particle pion wave functions of twist 4 and then extend the formalism to calculate the other couplings, ηNN, πΞΞ, ηΞΞ, πΣΣ and ηΣΣ. In the SU(3) symmetric limit, we identify the terms responsible for the F/D ratio in the OPE by matching the obtained couplings with their SU(3) relations. Depending on the Dirac structure considered, we find different identifications for the F/D ratio. The couplings including the SU(3) breaking effects are also discussed within our approach.