The measurement of strong-interaction shift and
broadening in pionic hydrogen and deuterium yields pion-nucleon
scattering lengths as well as the threshold pion-production strength
on isoscalar NN pairs. Results from recent high-resolution
experiments at PSI using crystal spectrometers allow important
comparisons with the outcome of the modern low-energy description of
QCD within the framework of effective field theories.
Measurement of charged-pion production in deep-inelastic scattering off nuclei with the CLAS detector