Pion scalar, vector, and tensor form factors from a contact interaction
Xiaobin Wang (School of Physics, Nankai University, Tianjin 300071, China); Zanbin Xing (School of Physics, Nankai University, Tianjin 300071, China); Jiayin Kang (School of Physics, Nankai University, Tianjin 300071, China); Khépani Raya (Department of Integrated Sciences and Center for Advanced Studies in Physics, Mathematics and Computation, University of Huelva, E-21071 Huelva, Spain); Lei Chang (School of Physics, Nankai University, Tianjin 300071, China)
The pion scalar, vector, and tensor form factors are calculated within a symmetry-preserving contact interaction model (CI) of quantum chromodynamics (QCD), encompassed within a Dyson-Schwinger and Bethe-Salpeter equations approach. In addition to the traditional rainbow-ladder truncation, a modified interaction kernel for the Bethe-Salpeter equation is adopted. The implemented kernel preserves the vector and axial-vector Ward-Takahashi identities, while also providing additional freedom. Consequently, new tensor structures are generated in the corresponding interaction vertices, shifting the location of the mass poles appearing in the quark-photon and quark tensor vertex and yielding a notorious improvement in the final results. Despite the simplicity of the CI, the computed form factors and radii are compatible with recent lattice QCD simulations.
