The Zcs(3985) as a threshold effect from the (D)over-bars*D + (D)over-barsD* interaction

We study the e(+)e(-) -> K+(D-s*D--(0) + Ds-D*(0)) reaction recently measured at BESIII, from where a new Z(cs) state has been reported. We study the interaction of (D) over bar D-s* with the coupled channels J/psi K-, K*(-)eta(c), Ds-D*(0), D-s*D--(0) by means of an extension to the charm sector of the local hidden gauge approach. We find that the Ds-D*(0) + D-s*D--(0) combination couples to J/psi K- and K*(-)eta(c), but the Ds-D*(0 ) -D-s*D--(0) combination does not. The coupled channels help to build up strength in the Ds-D*(0) + D-s*D--(0) diagonal scattering matrix close to threshold and, although the interaction is not strong enough to produce a bound state or resonance, it is sufficient to produce a large accumulation of strength at the (D) over bar D-s* threshold in the e(+)e(-) -> K+(D-s*D--(0) + Ds-D*(0)) reaction in agreement with experiment. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The study shows that the combination of Ds-D*(0) + D-s*D--(0) couples to J/psi K- and K*(-)eta(c), while the combination of Ds-D*(0) - D-s*D--(0) does not. The coupled channels help to accumulate strength in the reaction, which is crucial for interpreting the experimental results.