Testing in-medium $πN$ dynamics on pionic atoms

Abstract

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 $b_1$, or equivalently the renormalization of the pion decay constant $f_π$ in the nuclear medium.

V2 minor rephrasing, 15 pages, 3 figures, to be published in Nuclear Physics A special issue in memory of Gerry Brown