Search for Z_c^+(3900) in the 1^+- channel on the lattice
Recently three experiments reported a discovery of manifestly exotic Z_c^+(3900) in the decay to J/psi pi+, while J and P are experimentally unknown. We search for this state on the lattice by simulating the channel with J^PC=1^+- and I=1, and we do not find a candidate for Z_c^+(3900). Instead, we only find discrete scattering states D D* and J/psi pi, which inevitably have to be present in a dynamical QCD. The possible reasons for not finding $Z_c^+$ may be that its quantum numbers are not $1^{+-}$ or that the employed interpolating fields are not diverse enough. Simulations with additional types of interpolators will be needed to reach a more definite conclusion.