Measurement of $ep \to e^{'}p\pi^{+}\pi^{-}$ and baryon resonance analysis

TL;DR

This paper reports measurements of the $ep o e' p \, \pi^+ \pi^-$ reaction cross section in the resonance region, revealing new structures and discrepancies with existing models, suggesting possible new baryon states or resonance property modifications.

Contribution

It provides new experimental data on baryon resonance structures in a previously unexplored kinematic region, highlighting the need for revised resonance models or new states.

Findings

Resonant structures not seen before in the data.

Discrepancies with existing phenomenological models.

Potential evidence for a new baryon state or altered resonance properties.

Abstract

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