Interpreting Zc (3900) and Zc (4025)/Zc (4020) as charged tetraquark states

In the framework of the color flux-tube model with a four-body confinement potential, the lowest charged tetraquark states [Qq][(Q) over bar'(q) over bar'](Q = c; b, q = u, d, s) are studied by using the variational method, the Gaussian expansion method. The results indicate that some compact resonance states with threedimensional spatial structures can be formed. These states cannot decay into two color singlet mesons Qq (q) over bar' and (Q) over bar 'q through the breakdown and recombination of color flux tubes but into Q (Q) over bar' and q (q) over bar'. The fourbody confinement potential is a crucial dynamical mechanism for the formation of these compact resonance states. The decay process is similar to that of a compound nucleus but due to the multibody color confinement. The newly observed charged states Z(c)(3900) and Z(c)(4025) = Z(c)(4020) can be interpreted as the S-wave tetraquark states [cu][(c) over bar(d) over bar] with quantum numbers IJ(P) = 11(+) and 12(+), respectively.