First results on nucleon resonance photocouplings from the $\gamma p \to \pi^+\pi^-p$ reaction

Understand

We report the first experimental measurements of the nine 1-fold differential cross sections for the $\gamma p \to \pi^+\pi^-p$ reaction, obtained with the CLAS detector at Jefferson Laboratory.

• The measurements cover the invariant mass range of the final state hadrons from 1.6~GeV~$<W<$~2.0~GeV.
• For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel.
• Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the $\Delta(1620)1/2^-$, $\Delta(1700)3/2^-$, $N(1720)3/2^+$, and $\Delta(1905)5/2^+$ resonances, which have dominant decays into the $\pi\pi N$ final states rather than the more extensively studied single meson decay channels.