Renormalization of the isovector πN amplitude in pionic atoms Original Research Article

The extraction of the isovector s-wave πN amplitude from pionic atoms is studied with special emphasis on uncertainties and their dependence on the assumptions made regarding the neutron density distributions in nuclei and on the size of the data base used. Only ‘global’ analyses of pionic-atom data reveal a discrepancy between the extracted isovector s-wave πN amplitude b1=(−0.108±0.007)mπ−1 and its free πN counterpart View the MathML source, where the uncertainty in the neutron densities is included in the error analysis. The role of ‘deeply bound’ pionic atom states is discussed and the reason for failure of these states to provide new information is explained.