Meson–baryon couplings and the F/ D ratio from QCD sum rules

Abstract

Motivated by the recent work on the calculation of the πNN coupling constant using QCD sum rule beyond the chiral limit, we construct the corresponding sum rules for the couplings, ηNN, πΞΞ, ηΞΞ, πΣΣ and ηΣΣ. In constructing the η-baryon sum rules, we use the second moment of the η wave function, which we obtain from the pion wave function after SU(3) rotation. In the SU(3) symmetric limit, we can identify the term responsible for the F/ D ratio in the OPE, which after the sum rule analysis gives F/ D∼0.2, a factor of three smaller than from other studies. We also present a qualitative analysis including the SU(3) breaking terms.