Timelike pion form factor in lattice QCD

TL;DR

This paper presents a nonperturbative lattice QCD calculation of the timelike pion form factor, providing insights into its complex phase and modulus near the vector resonance using finite-volume techniques and multiple ensembles.

Contribution

The study introduces a lattice QCD approach to compute the timelike pion form factor at various energies, comparing results with phenomenological models.

Findings

Form factor computed at ten timelike momentum points

Results consistent with Gounaris-Sakurai model

Demonstrates effectiveness of finite-volume lattice techniques

Abstract

We perform a nonperturbative lattice calculation of the complex phase and modulus of the pion form factor in the timelike momentum region using the finite-volume technique. We use two ensembles of 2+1-flavor overlap fermion at pion masses m_pi = 380 and 290 MeV. By calculating the I = 1 correlators in the center-of-mass and three moving frames, we obtain the form factor at ten different values of the timelike momentum transfer around the vector resonance. We compare the results with the phenomenological model of Gounaris-Sakurai and its variant.