Testing in-medium πN dynamics on pionic atoms

A general algorithm for handling the energy dependence of meson–nucleon amplitudes in the nuclear medium has been recently applied to antikaons and to eta mesons. Here we test this approach on πN amplitudes in pionic atoms where direct comparison can be made with ample experimental results. Applying this algorithm to a large-scale fit of 100 pionic-atom data points across the periodic table, which also include the ‘deeply-bound’ states in Sn and Pb, reaffirms earlier conclusions on the density-dependent renormalization of the πN   threshold isovector amplitude b1b1, or equivalently the renormalization of the pion decay constant fπfπ in the nuclear medium.