Kolomeitsev, Evgeni E., 1970-

Chiral dynamics of deeply bound pionic atoms / Evgeni E. Kolomeitsev, N. Kaiser, W. Weise. -- We present and discuss a systematic calculation, based on two-loop chiral perturbation theory, of the pion-nuclear s-wave optical potential. A proper treatment of the explicit energy dependence of the off-shell pion self-energy together with (electromagnetic) gauge invariance of the Klein-Gordon equation turns out to be crucial. Accurate data for the binding energies and widths of the 1s and 2p levels in pionic Pb-205 and Pb-207 are well reproduced without need for a notorious "missing repulsion" in the pion-nuclear s-wave optical potential. The connection with the in-medium change of the pion decay constant is clarified.

In Physical Review Letters. -- Maryland : American Physical Society, 2003. -- ISSN 0031-9007. -- ISSN 1079-7114. -- Vol. 90, no. 9 (2003), pp. 2501-2501