Abstract

We examine the four-quark structure of the recently discovered charged Z(c)(3900), Z(4430), and X-b(5568) states. We calculate the widths of the strong decays Z(c)(+) -> J/psi pi(+) (eta(c)rho(+), (D) over bar D-0*+, (D) over bar*D-0(+)), Z(4430)(+) -> J/psi pi(+) (psi(2s)pi(+)), and X-b(+) -> B-s pi(+) within a covariant quark model previously developed by us. We find that the tetraquark-type current widely used in the literature for the Z(c)(3900) leads to a significant suppression of the (D) over barD* and (D) over bar *D modes. Contrary to this a molecular-type current provides an enhancement by a factor of 6-7 for the (D) over barD* modes compared with the Z(c)(+) -> J/psi pi(+), eta(c)rho(+) modes in agreement with recent experimental data from the BESIII Collaboration. In the case of the Z(4430) state we test a sensitivity of the ratio R-Z of the Z(4430)(+) -> psi(2s)pi(+) and Z94430)(+) -> J/psi pi(+) decay rates to a choice of the size parameter Lambda(Z(4430)) of the Z(4430). Using the upper constraint for the sum of these two modes deduced from the LHCb Collaboration data we find that R-Z varies from 4.64 to 4.08 when Lambda(Z(4430)) changes from 2.2 to 3.2 GeV. Also we make the prediction for the Z(4430)(+) -> D*(D) over bar*(0) decay rate.