R. Abou Yassine, J. Adamczewski-Musch, O. Arnold, E. T. Atomssa, M. Becker, C. Behnke, J. C. Berger-Chen, A. Blanco, C. Blume, M. Böhmer, L. Chlad, I Ciepał, S. Deb, C. Deveaux, D. Dittert, J Dreyer, E. Epple, L Fabbietti, J Förtsch, P. Fonte, C. Franco, J. Friese, I. Fröhlich, T Galatyuk, J.A. Garzón, R. Gernhäuser, R Greifenhagen, M Grunwald, M Gumberidze, S Harabasz, T Heinz, T. Hennino, C Höhne, F. Hojeij, R Holzmann, M. Idzik, B Kämpfer, K-H Kampert, B Kardan, V Kedych, S. Kim, I. Koenig, W. Koenig, M. Kohls, J Kolas, B. W. Kolb, G. Korcyl, G. Kornakov, R. Kotte, W. Krueger, A. Kugler, T. Kunz, R. Lalik, K. Lapidus, S. Linev, F. Linz, L. Lopes, M. Lorenz, T. Mahmoud, L. Maier, A. Malige, J. Markert, S. Maurus, V. Metag, J. Michel, D. M. Mihaylov, A. Molenda, C Müntz, R. Münzer, M Nabroth, L Naumann, K Nowakowski, A. Opíchal, J. Orliński, J. -H. Otto, Y. Parpottas, M. Parschau, C. Pauly, V. Pechenov, O. Pechenova, K Piasecki, J. Pietraszko, T. Povar, K Prościński, A. Prozorov, Witold Wojciech Przygoda, K. Pysz, B. Ramstein, N. Rathod, P. Rodríguez-Ramos, A. Rost, A. Rustamov, P. Salabura, K Scharmann, T. Scheib, N Schild, K. Schmidt-Sommerfeld, H. Schuldes, E Schwab, F. Scozzi
First information on the time-like electromagnetic structure of baryons in the second resonance region has been obtained from measurements of dielectron (e+ e-) invariant-mass and angular distributions in the quasi-free reaction $π-$ p $\rightarrow$ n e+ e- at $\sqrt{s_{πp}}$ = 1.49 GeV with the High Acceptance Di-Electron Spectrometer (HADES) at GSI using the pion beam impinging on a CH$_2$ target. We find a total cross section $σ$ = 2.97 $\pm$ 0.07data $\pm$ 0.21acc $\pm$ 0.31Zeff $μ$b. In complement to the analysis of the inclusive e+ e- channel, this data set provides a crucial test of the description of baryon time-like transitions. Approaches based on a Vector Meson Dominance amplitude containing direct photon and vector meson ($ρ$) couplings to the baryon provide a satisfactory agreement with the data. A good description is also obtained by electromagnetic time-like baryon transition form factors in a covariant spectator-quark model, pointing to the dominance of meson-cloud effects. The dielectron angular distributions exhibit the contributions of virtual photons ($γ^*$) with longitudinal polarization, in contrast to real photons. The virtual photon angular dependence supports the dominance of J=3/2, I=1/2 contributions observed in both the $γ^*$n and the $ππ$n channels.