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

TL;DR

This paper investigates the $m{ ext{pi}^- p o n e^+ e^-}$ reaction at 1.49 GeV using an effective-Lagrangian model, highlighting the roles of non-resonant and resonant contributions, and providing predictions for cross sections and spin observables.

Contribution

The study extends an effective-Lagrangian model by including a phenomenological phase factor at the $RN ho$ vertex, offering new insights into resonance contributions in the reaction.

Findings

Cross section dominated by Born and $N(1520)$ contributions.

Predictions provided for differential cross section and spin density matrix elements.

Model includes non-resonant and resonant terms with a phenomenological phase factor.

Abstract

We present a study of the reaction $\pi^-p \to ne^+e^-$ for $\sqrt{s}=1.49\,\textrm{GeV}$, 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.