Charge form factors of quark-model pions

Experimental data of the pion charge form factor are well represented by Poincaré invariant constituent-quark phenomenology depending on two parameters: a confinement scale and an effective quark mass. Pion states are represented by eigenfunctions of mass and spin operators and of the light-front momenta. An effective current density is generated by the dynamics from a null-plane impulse current density. A simple shape of the wave function depending only on the confinement scale is sufficient. The range of quark masses and confinement scales consistent with both low- and high-$Q^2$ data depends on the shape of the wave function.