Role of baryon resonances in the ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ reaction within an effective-Lagrangian model

Abstract

We present a study of the reaction ${\pi }^{-}p\to n{e}^{+}{e}^{-}$ for $\sqrt{s}=1.49\text{GeV}$, including non-resonant Born terms and contributions of the $N(1440)$, $N(1520)$, $N(1535)$ resonances ($R$), using an effective-Lagrangian model, which we extended by a phenomenological phase factor at the $RN\rho$ vertex function. We give predictions for both the differential cross section $d\sigma /dm$ and the spin density matrix elements of the virtual photon that decays into the lepton pair. In the studied energy range, the cross section is dominated by the Born and $N(1520)$ contributions.

Comments: 22 pages, 6 figures; data files for Figures 2-6 are provided