Abstract
We study the two point correlation function of two nucleon currents sandwiched between the vacuum and the pion state. The light cone QCD sum rules are derived for the $\ensuremath{\pi}\mathrm{NN}$ coupling ${g}_{\ensuremath{\pi}\mathrm{NN}}$ and the $\ensuremath{\pi}\mathrm{NN}(1535)$ coupling ${g}_{\ensuremath{\pi}{\mathrm{NN}}^{*}}.$ The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with respect to the two external momenta ${p}_{1}^{2}, {p}_{2}^{2}=(p\ensuremath{-}{q)}^{2}.$ We first improve the original sum rule for ${g}_{\ensuremath{\pi}\mathrm{NN}}$ and determine the value of the pion wave function ${\ensuremath{\varphi}}_{\ensuremath{\pi}}{(u}_{0}=\frac{1}{2})=1.5\ifmmode\pm\else\textpm\fi{}0.2,$ which is a fundamental nonperturbative quantity similar to the quark condensate. Our calculation shows that the $\ensuremath{\pi}\mathrm{NN}(1535)$ coupling is strongly suppressed.
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