Dynamical diquarks in the transition

K. Raya; L. X. Gutiérrez-Guerrero; A. Bashir; L. Chang; Z.-F. Cui; Y. Lu; C. D. Roberts; J. Segovia

doi:10.1140/epja/s10050-021-00574-w

2023 Impact factor 2.6

Hadrons and Nuclei

Eur. Phys. J. A (2021) 57: 266
https://doi.org/10.1140/epja/s10050-021-00574-w

Regular Article - Theoretical Physics

Dynamical diquarks in the $γ^{()} p \to N (1535) {\frac{1}{2}}^{-}$ ${\varvec{\gamma ^{()} p\rightarrow N(1535)\frac{1}{2}^-}}$ transition

K. Raya¹^,2, L. X. Gutiérrez-Guerrero³, A. Bashir⁴, L. Chang¹, Z.-F. Cui⁵^,6, Y. Lu⁵^,6, C. D. Roberts⁵^,6^g and J. Segovia⁶^,7

¹ School of Physics, Nankai University, 300071, Tianjin, China
² Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, 04510, Mexico, CDMX, México
³ CONACyT-Mesoamerican Centre for Theoretical Physics, Universidad Autónoma de Chiapas, Carretera Zapata Km. 4, Real del Bosque (Terán), Tuxtla Gutiérrez, 29040, Chiapas, México
⁴ Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, 58040, Morelia, MICH, México
⁵ School of Physics, Nanjing University, 210093, Nanjing, Jiangsu, China
⁶ Institute for Nonperturbative Physics, Nanjing University, 210093, Nanjing, Jiangsu, China
⁷ Dpto. Sistemas Físicos, Químicos y Naturales, Univ. Pablo de Olavide, 41013, Sevilla, Spain

^g cdroberts@nju.edu.cn

Received: 4 August 2021
Accepted: 6 August 2021
Published online: 4 September 2021

Abstract

The $γ^{(*)} + p \to N (1535) {\frac{1}{2}}^{-}$ $\gamma ^{(*)}+p \rightarrow N(1535) \tfrac{1}{2}^-$ transition is studied using a symmetry-preserving regularisation of a vector $\otimes$ $\,\otimes \,$ vector contact interaction (SCI). The framework employs a Poincaré-covariant Faddeev equation to describe the initial and final state baryons as quark+diquark composites, wherein the diquark correlations are fully dynamical, interacting with the photon as allowed by their quantum numbers and continually engaging in breakup and recombination as required by the Faddeev kernel. The presence of such correlations owes largely to the mechanisms responsible for the emergence of hadron mass; and whereas the nucleon Faddeev amplitude is dominated by scalar and axial-vector diquark correlations, the amplitude of its parity partner, the $N (1535) {\frac{1}{2}}^{-}$ $N(1535) \tfrac{1}{2}^-$ , also contains sizeable pseudoscalar and vector diquark components. It is found that the $γ^{(*)} + p \to N (1535) {\frac{1}{2}}^{-}$ $\gamma ^{(*)}+p \rightarrow N(1535) \tfrac{1}{2}^-$ helicity amplitudes and related Dirac and Pauli form factors are keenly sensitive to the relative strengths of these diquark components in the baryon amplitudes, indicating that such resonance electrocouplings possess great sensitivity to baryon structural details. Whilst SCI analyses have their limitations, they also have the virtue of algebraic simplicity and a proven ability to reveal insights that can be used to inform more sophisticated studies in frameworks with closer ties to quantum chromodynamics.