Measurement of $ep\ensuremath{\rightarrow}{e}^{\ensuremath{'}}p{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and Baryon Resonance Analysis

Measurement of $e p \to e^{'} p π^{+} π^{-}$ and Baryon Resonance Analysis

M. Ripani et al. (CLAS Collaboration)

Phys. Rev. Lett. 91, 022002 – Published 11 July 2003

Abstract

The cross section for the reaction $e p \to e^{'} p π^{+} π^{-}$ was measured in the resonance region for $1.4 < W < 2.1 G e V$ and $0.5 < Q^{2} < 1.5 {G e V}^{2} / c^{2}$ using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on $N^{*}$ and $Δ$ states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the $P_{13} (1720)$ resonance or by introducing a new baryon state, not reported in published analyses.