A simple parametrisation of the pion form factor

Kirk, Matthew; Kubis, Bastian; Reboud, Méril; van Dyk, Danny

Abstract

We discuss a novel and simple parametrisation of the pion vector form factor that transparently connects spacelike and timelike regions of the momentum transfer q2. Our parametrisation employs the framework of conformal mapping and respects the known analyticity properties of the form factor, accounting explicitly for the ρ(770)-meson pole. The parametrisation manifestly fulfils the normalisation condition at q2=0 as well as further restrictions at the pion production threshold and in the limit |q2|→∞. In contrast to the widely used Omnès parametrisation, our approach does not use the pion–pion scattering phase shift as input. We confront the parametrisation with experimental data from πH scattering and τ−→π−π0ν decay. We already find a good description of the data with only five free parameters, which include the pole mass and decay width of the ρ(770).

Citation

Kirk, M., Kubis, B., Reboud, M., & van Dyk, D. (2025). A simple parametrisation of the pion form factor. Physics Letters B, 861, Article 139266. https://doi.org/10.1016/j.physletb.2025.139266

• Journal Article Type: Article
• Acceptance Date: Jan 14, 2025
• Online Publication Date: Jan 16, 2025
• Publication Date: Feb 1, 2025
• Deposit Date: Mar 24, 2025
• Publicly Available Date: Mar 24, 2025
• Journal: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
• Print ISSN: 0370-2693
• Electronic ISSN: 1873-2445
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 861
• Article Number: 139266
• DOI: https://doi.org/10.1016/j.physletb.2025.139266
• Public URL: https://durham-repository.worktribe.com/output/3739541