Two-meson form factors in unitarized chiral perturbation theory

• Published in: The journal of high energy physics 2021-04, Vol.2021 (4), p.1-55, Article 86
• Main Authors: Shi, Yu-Ji, Seng, Chien-Yeah, Guo, Feng-Kun, Kubis, Bastian, Meißner, Ulf-G., Wang, Wei
• Format: Article
• Language: English
• Subjects: Chiral dynamics; Chiral Lagrangians; Classical and Quantum Gravitation; Cosmology; Dispersion; Elementary Particles; Energy; Form factors; Heavy Quark Physics; High energy physics; Laboratories; Leptons; Mathematical analysis; Mesons; Perturbation theory; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Regular Article - Theoretical Physics; Relativity Theory; Standard model (particle physics); String Theory; Tensors; Theoretical physics
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP04(2021)086

A bstract We present a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators. The theoretical framework is based on a combination of unitarized chiral perturbation theory and dispersion relations. The low-energy constants in chiral perturbation theory are fixed by a global fit to the available data of the two-meson scattering phase shifts. Each form factor derived from unitarized chiral perturbation theory is improved by iteratively applying a dispersion relation. This study updates the existing results in the literature and explores those that have not been systematically studied previously, in particular the two-meson tensor form factors within unitarized chiral perturbation theory. We also discuss the applications of these form factors as mandatory inputs for low-energy phenomena, such as the semi-leptonic decays B s → π + π − ℓ + ℓ − and the τ lepton decay τ → π − π 0 ν τ , in searches for physics beyond the Standard Model.