Z_c(3900): Experiment, Theory, Lattice

Abstract

The resonant structure Z c (3885)/Z c (3900) is studied in a unitary, J/ψπ-D * D coupled channel Tmatrix formalism. The two experimental spectra (D * D , J/ψπ) in which this state is seen are reproduced in two different scenarios. In the first one, the Z c originates from a resonance with a mass close to and above the DD * threshold. In the second one, the Z c peak stems from a virtual state. In both scenarios the two observations, Z ± c (3900) and Z ± c (3885), are shown to have the same common origin. We further consider our T -matrix in a finite box, computing energy levels that are compared with a recent Lattice QCD simulation. We find both scenarios compatible with the LQCD results.