Role of rescattering in pion photoproduction at threshold

It is shown that rescattering corrections to γp→${\pi }^0$p through the sequence γp→${\pi }^{+}$n→${\pi }^0$p, at threshold, and to γn→${\pi }^0$n through the sequence γn→${\pi }^{\mathrm{-}}$p→${\pi }^0$n, are large. The cusps at ${\pi }^{+}$n and ${\pi }^{\mathrm{-}}$p thresholds, $k_L$=151.5 and 148.5 MeV, respectively, are inverted. It is also argued that an explanation of the discrepancy between experiment and theory through a Σ-like term is, most likely, erroneous.