$g_{NK\Lambda}$ and $g_{NK\Sigma}$ from QCD Sum Rules in the $\gamma_5 \sigma_{\mu \nu}$ structure

Abstract

The NKY coupling constant for $Y = \Lambda$ and $\Sigma$ is evaluated in a QCD sum rule calculation. We study the Borel sum rule for the three point function of one pseudoscalar one nucleon and one hyperon current up to order six in the operator product expansion. The Borel transform is performed with respect to the nucleon and hyperon momenta, which are taken to be equal. We discuss and extend the result of a previous analysis in the $\rlap{/}{q}i\gamma_5$ structure and compare it with the result obtained with the use of the $\gamma_5 \sigma_{\mu \nu}$ structure. We find that the effect of pole-continuum transitions is very important in the $\rlap{/}{q}i\gamma_5$ structure and that it changes completely results obtained in previous analysis.