Construction of the pion scalar form factor from few poles and zero

Abstract

Construction and analysis of the pion scalar-isoscalar form factor in the elastic region is presented. Precise S-wave ππ scattering phase shifts generated by dispersive analysis of experimental data with imposed crossing symmetry condition are used. Final result for values of the f0(500) meson mass and width, mσ = (487 ± 31) MeV; Γσ = (542 ± 60) MeV is compatible with the results from dispersive analyses of the Bern and Madrid-Kraków groups to be considered now as the most reliable values of the f0(500) scalar meson parameters. Parameters of the f0(980), although lying almost on the KK̄ threshold also agree with values predicted by these two groups.