Comment on "Scrutinizing pion-pion scattering in light of recent lattice phase shifts"
Abstract
In a recent paper by Xiu-Li Gao, Zhi-Hui Guo, Zhiguang Xiao, and Zhi-Yong Zhou, Phys. Rev. D 105, 094002 (2022), here referred to as I, S-wave ππ scattering phase shifts obtained in a lattice-QCD calculation are analyzed using dispersive S-matrix methods. We question the reliability of the conclusion from this analysis that, for a pion mass of 391 MeV, the lattice phases favor the presence of both a σ-meson bound state and a nearby virtual state. Our main criticism concerns the neglect of the S-wave KK channel, which was considered alongside additional ss interpolating fields in the lattice computation used by the authors of I and also in typical coupled-channel models. As an illustration, some results from such a recent model are presented as well. Concluding remarks concern possible improvements of the analysis in I as well as further model tests.