Neutron radii of calcium isotopes from pion total cross section measurements

Measurements of the total cross section differences sigma/sub T/(/sup 48/Ca) - sigma/sub T/(/sup 40/Ca) and sigma/sub T/(/sup 44/Ca) - sigma/sub T/(/sup 44/Ca) are reported for positive and negative pions. Optical-model calculations are used to extract values of the rms neutron radius difference for each isotope pair. For /sup 48/Ca-/sup 40/Ca the deduced radius difference agrees with the results of recent ..cap alpha..-particle and proton scattering experiments but is smaller than values predicted from Hartree-Fock calculations.