About the exotic structure of Zcs

Very recently a new hadronic structure around 3.98GeV was observed in BESIII experiment. From its decay modes, it is reasonable for people to assign it to the category of exotic state, say Z(cs)(+), the stranged-parter of Z(c)(3900). This finding indicates for the first time the tetraquark with strange quark in hidden-charm sector, and hence has a peculiar importance. By virtue of the QCD Sum Rule technique, we analyze the Z(cs)(+) about its possible configuration and physical properties, and find it could be configured as a mixture of two types of structures, [1(c)]((c) over baru) circle times [1(c)]((c) over barc) and [1(c)]((c)Z() over barc) circle times [1(c)]((c) over baru), or [(3) over bar (c)]((c) over baru) circle times [3(c)]((c) over barc) and [3(c)]((c) over barc) circle times [<(3())over bar>(c)] ((s) over baru), with J(P)= 1(+). Physically, it then appears to be the emergence of a compound of four possible currents in each configuration, which tells that the single current evaluation of hadron spectroscopy and their decay properties are sometimes not enough. We find that in both cases the energy spectra may fit well with the experimental observation within the uncertainties, i.e. 3.98GeV, while be noted that the molecular state is not favored by vector-meson-exchange model. Various Z(cs)(+) (3980) decay modes are evaluated, which are critical for pinning down its configuration and left for experimental verification. We also predict the mass of Z(cs)(0), the neutral partner of Z(cs)(+)(3980), and analyze its dominant decay probabilities. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

A new hadronic structure around 3.98GeV, potentially an exotic state Z(cs)(+), was recently observed in the BESIII experiment. This finding is significant for revealing the tetraquark with strange quark in the hidden-charm sector. By using the QCD Sum Rule technique, the possible configuration and physical properties of Z(cs)(+) were analyzed, suggesting it may be a mixture of two types of structures.