Extracting σ_πn from pionic atoms

We discuss a recent extraction of the πN σ term σ_πN from a large-scale fit of pionic-atom strong-interaction data across the periodic table. The value thus derived, σ_πN ^FG = 57 ± 7 MeV, is directly connected via the Gell-Mann–Oakes–Renner expression to the medium-renormalized πN isovector scattering amplitude near threshold. It compares well with the value derived recently by the Bern–Bonn–Jülich group, σ_πN ^RS = 58 ± 5 MeV, using the Roy–Steiner equations to control the extrapolation of the vanishingly small near-threshold πN isoscalar scattering amplitude to zero pion mass.