Triangle diagram in heavy-baryon chiral perturbation theory

Songlin Lyu, Bingwei Long

The pion-baryon triangle diagram is inspected for a special kinematic region where the squared momentum transfer $t$ is close to $4m_{\pi }^2$: $|t-4m_{\pi }^2|\lesssim m_{\pi }^4/m_N^2$. Inst…