Inverse pion electroproduction at threshold π-p→ne+e- and neutral pion Dalitz decay π0 → γe+e-

Inverse pion electroproduction at threshold (1) and neutral pion Dalitz decay (2) are investigated with stopped pions. The experiment uses the pion beam at the Saclay Linear Accelerator, a liquid hydrogen target, and a double-arm magnetic spectrometer for the lepton pair detection. A differential analysis yields the dynamics of processes (1) and (2), thus testing theoretical models for strong interaction at low energies. For process (1), a transverse-longitudinal-separation based on photon squared mass and polarization, gives a measurement of the s-wave multipoles: in relative (transverse electric) or absolute value (longitudinal multipole). Process (2) gives a measurement of the neutral pion electromagnetic transition form factor, and slope parameter