First Results on Nucleon Resonance Electroexcitation Amplitudes from $ep\to e'\pi^+\pi^-p'$ Cross Sections at $W$ from 1.4-1.7 GeV and $Q^2$ from 2.0-5.0 GeV$^2$

TL;DR

This paper reports the first extraction of nucleon resonance electroexcitation amplitudes from $ep o e'\pi^+\pi^-p'$ cross sections, covering a range of energies and photon virtualities, revealing insights into resonance structures and quark-meson interactions.

Contribution

First determination of electrocouplings for several nucleon resonances from $ ext{ep} o e' ext{ }\pi^+ ext{ }\pi^- ext{ }p'$ data across multiple energy and $Q^2$ ranges.

Findings

Electrocouplings of $N(1440)1/2^+$ and $N(1520)3/2^-$ extended over broader $Q^2$.

First extraction of $ ext{Delta}(1600)3/2^+$ electrocouplings.

Evidence for resonance structure involving quark core and meson-baryon cloud.

Abstract

The electroexcitation amplitudes or $\gamma_vpN^*$ electrocouplings of the $N(1440)1/2^+$, $N(1520)3/2^-$, and $\Delta(1600)3/2^+$ resonances were obtained for the first time from the $ep \to e'\pi^+\pi^-p'$ differential cross sections measured with the CLAS detector at Jefferson Lab within the range of invariant mass $W$ of the final state hadrons from 1.4--1.7 GeV for photon virtualities $Q^2$ from 2.0--5.0 GeV$^2$. The electrocouplings were determined in independent fits of the $\pi^+\pi^-p$ cross sections within three overlapping $W$ intervals with a substantial contribution from each of the three resonances listed above. Consistent results on the electrocouplings extracted from the data in these $W$ intervals provide evidence for their reliable extraction. These studies extend information on the electrocouplings of the $N(1440)1/2^+$ and $N(1520)3/2^-$ available from this channel over a broader range of $Q^2$. The electrocouplings of the $\Delta(1600)3/2^+$, which decays preferentially into $\pi\pi N$ final states, have been determined for the first time. Our results provide further evidence for the structure of these resonances in terms of an interplay between the inner core of three dressed quarks and an external meson-baryon cloud.