Comment on ‘‘Pion-nucleon partial-wave analysis to 2 GeV’’

At incident pion energies below 150 MeV, values for the pion charge exchange cross section, derived from the pion-nucleon partial-wave analysis by Arndt et al., are slightly in error because a factor of ${\mathit{p}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$X/${\mathit{p}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ has been neglected, ${\mathit{p}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$X and ${\mathit{p}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ are the momenta of the scattered neutral and charged pions in the center-of-mass frame, respectively. In addition, an oversight in the center-of-mass to laboratory kinematic transformations has been discoverd in the Scattering Analysis Interactive Dial-in (said) system, a system through which the aforementioned pion-nucleon partial-wave analysis may be accessed. This oversight, in which the mass differences between charged and neutral pions and between protons and nuetrons have been neglected, introduces systematic energy and angular dependent errors to the laboratory differential cross section for pion charge exchange below 150 MeV.