Eta-meson Couplings with Low-Lying Nucleon Resonances

Using QCD sum rules, supplemented with projected correlation function approach, we have calculated coupling constants of an eta-meson with the two lowest mass nucleon resonances. This includes both the diagonal as well as non-diagonal coupling constants involving a nucleon resonance and a nucleon. For this, we first calculate vacuum-to-eta correlation function of the interpolating fields of two nucleons and then take its matrix elements with respect to a nucleon spinor and/or a nucleon resonance spinor(s). Desired coupling constants are obtained by solving different equations obtained from different matrix elements. Stability of the results with respect to variation of different QCD and phenomenological input parameters has been checked. We have also analyzed the effect of the changes in the coupling constants under the hypothetical situation when the contribution of the hidden strangeness is removed and when that of the anomalous glue is removed from the correlation function.