Chiral dynamics and pionic 1s states of Pb and Sn isotopes

Abstract

We calculate shifts and width of 1s and 2p states of pions bound to heavy nuclei, using an optical potential with its s-wave interaction part based on chiral symmetry. This potential is constructed systematically in two-loop approximation of chiral perturbation theory. A proper treatment of the explicit energy dependence of this potential in conjunction with gauge invariance turns out to be very important. Results are reported for deeply bound pionic states in Pb and Sn isotopes in comparison with the GSI data