We study the $\pi N\to \varphi N$ reaction close to the $\varphi N$ threshold within the chiral unitary approach, by combining the ${\pi }^{-}p\to K^{+}{\Sigma }^{-},{\pi }^{-}p\to K^0{\Sigma }^0$, and ${\pi }^{-}p\to K^0\Lambda$ amplitudes with the coupling of ϕ to the $K$ components of the final states of these reactions via quantum loops. We obtain good agreement with experiment when the dominant ${\pi }^{-}p\to K^0\Lambda$ amplitude is constrained with its experimental cross section. We also evaluate the coupling of $N^{*}(1535)$ to $\varphi N$ and find a moderate coupling as a consequence of partial cancellation of the large $\mathit{KY}$ components of $N^{*}(1535)$. We also show that the $N^{*}(1535)$ pole approximation is too small to reproduce the measured cross section for the ${\pi }^{-}N\to \varphi N$ reaction.

• Received 13 May 2008

DOI:https://doi.org/10.1103/PhysRevC.78.025207