Probing hidden-charm pentaquarks from the π Nrightarrow J/psi N reaction

We investigate the dynamical generation of hidden-charm pentaquark resonances in the $\pi N \to J/\psi N$ reaction utilizing an off-shell coupled-channel formalism. Motivated by the absence of pentaquark signals in $J/\psi$ photoproduction, we evaluate rescattering effects with two-body kernel amplitudes constructed from effective Lagrangians that explicitly incorporate $t$-channel meson and $u$-channel baryon exchanges. We demonstrate that the $u$-channel $\Lambda_c$ exchange, of which an analogous contribution is absent in the photoproduction kernel, greatly enhances the rescattering contributions through the $\bar{D}^{(*)}\Sigma_c$ intermediate states. Consequently, the $\bar{D}^{(*)}\Sigma_c^{(*)}$ channels yield contributions of comparable magnitude to the $\bar{D}^{(*)}\Lambda_c$ channels, directly leading to prominent pentaquark signals. The partial-wave analysis reveals that the $P_{c\bar{c}}(4312)$ and $P_{c\bar{c}}(4457)$ states emerge as clear peak structures with $J^P=1/2^-$ and $3/2^-$, respectively. In contrast, the $P_{c\bar{c}}(4380)$ and $J^P=5/2^-$ states are strongly suppressed because the $\Lambda_c$ exchange does not provide the required tensor interactions. The result for the total cross section reaches the microbarn level at the peak positions.