ON THE DETERMINATION OF THE PION EFFECTIVE-MASS IN NUCLEI FROM PIONICATOMS

The binding energies of the deeply bound 1s and 2p states in pionic at oms of Pb-207, recently established experimentally in the Pb-208(d,He- 3) reaction, have been used by several groups to derive the pion effec tive mass in nuclear matter. We show that these binding energies are f ully consistent with 'normal' pionic atoms and that the real part of t he pion-nucleus potential at the center of Pb-207 is 28 +/- 3 MeV and not 20 MeV as suggested previously. (C) 1998 Elsevier Science B.V. All rights reserved.