${\gamma }^{(\ast )}+\mathbf{N}(940){\frac{1}{2}}^{+}\to \mathbf{N}(1520){\frac{3}{2}}^{-}$ helicity amplitudes and transition form factors

Abstract

We recently reported new results on the ${\gamma }^{(\ast )}+N(940){\frac{1}{2}}^{+}\to \Delta (1700){\frac{3}{2}}^{-}$ transition form factors using a symmetry-preserving treatment of a vector$\otimes$vector contact interaction (SCI) within a coupled formalism based on the Dyson-Schwinger, Bethe-Salpeter, and Faddeev equations. In this work, we extend our investigation to the ${\gamma }^{(\ast )}+N(940){\frac{1}{2}}^{+}\to N(1520){\frac{3}{2}}^{-}$ transition. Our computed transition form factors show reasonable agreement with experimental data at large photon virtualities. However, deviations emerge at low $Q^2$, where experimental results exhibit a sharper variation than theoretical predictions. This discrepancy is expected, as these continuum QCD analyses account only for the quark-core of baryons, while low photon virtualities are dominated by meson cloud effects. We anticipate that these analytical predictions, based on the simplified SCI framework, will serve as a valuable benchmark for more refined studies and QCD-based truncations that incorporate quark angular momentum and the contributions of scalar and vector diquarks.

Comments: 9 pages, 8 figures