Systematic calculation of s-wave pion and kaon self-energies in asymmetricnuclear matter

We calculate the pion self-energies in asymmetric nuclear matter in the two -loop approximation of chiral perturbation theory. We find three types of c orrections beyond the well-known linear density approximation. The resultin g s-wave potential (or equivalent mass-shift) of a pi (-) in the center of a heavy nucleus like Pb turns out to be Upi- = Delta (m pi-) similar or equ al to 14 MeV, about half of what is needed to form the deeply hound and nar row pionic atom-states recently observed at GSI. The potential for a pi (+) under the same conditions is Upi+ = Deltam(pi+) similar or equal to -1 MeV . In the same way we calculate the mass shifts of K+-mesons in symmetric nu clear matter and neutron matter and find an increase of the K+-mass by 9% a nd 5%, respectively. As a further application we give an analytical result for the third order term in the scattering length expansion of the in-mediu m self-energy of an interacting light-bosun/heavy-fermion system. (C) 2001 Elsevier Science B.V. All rights reserved.