The pion, a strongly, electromagnetically and weakly interacting probe of nuclear structure

The technical advances in spectrometer design and beam intensity provided by the three meson factories at LAMPF (Los Alamos, New Mexico, USA), SIN (Villigen, Switzerland) and TRIUMF (Vancouver, British Columbia, Canada) have put pion reactions experimentally on a nearly equal level with other medium energy hadronic and electromagnetic probes of nuclear structure. Illustrative examples from recent experimental work are used to demonstrate the different nuclear excitation mechanism available through the various ways a pion may interact with nuclei. Radiative pion capture and photo-pion production on nuclei are shown to be sensitive to the spin-isospin response and enhancement of nuclear pion field and thus complement other, conventional electromagnetic probes such as electron scattering. Lastly radiative muon capture, where the pion enters through the one-pion exchange contribution dominating the induced psuedoscalar coupling of the semileptonic weak interaction, is being discussed