A new look for the pion form factor

by Dr Matthew Kirk (IPPP, Durham, UK)

Friday 21 Mar 2025, 14:00 → 15:00 Europe/London

In this talk, I will discuss a novel and simple parametrisation of meson form factors that can be used to describe data above and below the pair production threshold, using the pion form factor as a simple example (in which case our parameterisation describes both $\pi^+ \to \pi^0$ and $0 \to \pi \pi$ processes). To start with, I will introduce and walk through the derivation of dispersive bounds on form factors, then explain the difficulties in the traditional approach with a description of the above threshold data due to resonant poles, and the known asymptotic properties of the form factor in this region. Using data from $\pi$-H scattering and the $\tau \to \pi \pi \nu$ decay, I will show how with less than 5 free parameters (including the rho mass and decay width), we can excellently describe the data. This talk is based on my work in arXiv:2410.13764.