First results on nucleon resonance electroexcitation amplitudes from ep → e'π+π–p' cross sections at W = 1.4–1.7 GeV and Q2 = 2.0–5.0 GeV2

• Published in: Physical review. C 2023-08, Vol.108 (2)
• Main Authors: Mokeev, V. I., Achenbach, P., Burkert, V. D., Carman, D. S., Gothe, R. W., Hiller Blin, A. N., Isupov, E. L., Joo, K., Neupane, K., Trivedi, A.
• Format: Article
• Language: English
• Subjects: Baryons; Charged double pion photo- and electroproduction; Exclusive meson photo- and electroproduction; Lepton induced nuclear reactions; Particle interactions; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Structure of Nucleon resonances
• ISSN: 2469-9985
• DOI: 10.1103/PhysRevC.108.025204

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$^2$. A good description of the nine independent one-fold differential $\gamma_v p\to \pi^+\pi^-p'$ cross sections achieved within the data-driven Jefferson Lab-Moscow State University (JM) meson-baryon reaction model in each bin of ($W$,$Q^2$) allows for separation of the resonant and non-resonant contributions. The electrocouplings were determined in the 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. Here, the reliable extraction of the electrocouplings for these states is also supported by the description of the $\pi^+\pi^-p$ differential cross sections with $Q^2$-independent masses and total/partial hadronic decay widths into the $\pi\Delta$ and $\rho p$ final states.