Speaker
Description
A very important contribution of dilepton production in pion-nucleon collisions comes from the Dalitz decay of $s$-channel baryon resonances, $R \to N e^+ e^-$. These dileptons originate from a virtual photon with small timelike squared four-momentum $q^2$, therefore the study of this reaction gives access to the electromagnetic interaction of baryon resonances in a kinematical domain inaccessible elsewhere. In this contribution, we discuss what space-time symmetries teach us about the anisotropy of dileptons in $\pi^+N \to Ne^+e^-$. Then we present an effective Lagrangian model and its predictions for the cross-section of the reaction. These predictions will be compared to recent experimental results obtained by the HADES collaboration in pion beam experiments at the CM energy of 1.49 GeV where baryons of the second resonant region are expected to give important contributions.
