On the determination of the pion effective mass in nuclei from pionic atoms

The binding energies of the deeply bound 1s and 2p states in pionic atoms of 207Pb, recently established experimentally in the 208Pb(d,3He) reaction, have been used by several groups to derive the pion effective mass in nuclear matter. We show that these binding energies are fully consistent with `normalʹ pionic atoms and that the real part of the pion-nucleus potential at the center of 207Pb is 28±3 MeV and not 20 MeV as suggested previously.