Finite-range effects in pionic atoms

Finite-range effects on the strong-interaction level shifts and widths in pionic atoms were studied systematically throughout the periodic table by devising and solving the appropriate integro-differential wave equation in coordinate space. A novel method of expansion about zero range was used, enabling us to fit parameters of the pion-nuclear optical potential so that good agreement was obtained between calculation and experiment for a comprehensive set of data. The best-fit value for the r.m.s. radius of the p-wave πNN form factor is (0.34±0.15) fm. This small value is consistent with several analyses of other types of strong-interaction data. (orig.)