Precise determination of the pole position of the exotic Zc(3900)

Abstract

We perform a unified description of the experimental data of the π⁺π⁻ and J/ψπ^± invariant mass spectra for e⁺e⁻ → J/ψπ⁺π⁻ and the D⁰D^*− mass spectrum for e⁺e⁻ → D⁰D^*−π⁺ at e⁺e⁻ center-of-mass energies 4.23 and 4.26 GeV. The analysis takes into account open-charm meson loops that contain triangle singularities, the \(J/\psi\pi-D{\bar D}^*\) coupled-channel interaction respecting unitarity, and the strong \(\pi\pi-K{\bar K}\) final state interaction using dispersion relations. The analysis leads to a precise determination of the Z_c(3900) pole with the pole mass and width (3880.7 ± 1.7_stat ± 22.4_syst) MeV and (35.9 ± 1.4_stat ± 15.3_syst) MeV, respectively, and hints at that the \(D{\bar D}^*\) molecular and non-molecular components are of similar importance in the Z_c(3900) formation.