Speaker
Description
The internal structure of charged mesons can be probed through their electromagnetic form factors, which are rigorously connected to the transverse charge density via a two-dimensional Fourier transform. In this talk, we present a dispersive analysis of the timelike electromagnetic form factor of the charged pion, based on a logarithmic dispersion relation applied to the precise $e^+e^− \to \pi^+\pi^-$ data up to 3 GeV. This approach enables a model-independent extraction of both the modulus and phase of the form factor, circumventing the difficulties of standard unitarity-based methods above the elastic region.
Our method yields an extraction of the transverse charge density at the percent-level accuracy for distances $b \gtrsim 0.1$ fm. At shorter distances, where pQCD effects become relevant, we explore the implications of different high-energy assumptions through sum rules. These tests provide critical information about the onset of pQCD dynamics in exclusive processes and the expected double-logarithmic behavior of the density at small distances.
