Investigation of box diagrams for the peak of $Z_{cs}(3985)$ in $e^{+}{e}^{-}\to D_s^{-}{D}^{\ast 0}{K}^{+}$ and $D_s^{\ast -}{D}^0{K}^{+}$

Abstract

The BESIII collaboration recently observed a charged hidden-charm structure with strangeness in the recoil mass spectrum of $K^{+}$ in the processes $e^{+}{e}^{-}\to D_s^{-}{D}^{\ast 0}{K}^{+}$ or $D_s^{\ast -}{D}^0{K}^{+}$, named as $Z_{cs}(3985{)}^{-}$. Within the energy region around the peak of $Z_{cs}(3985)$, various box diagrams are present. A systematic study of these box diagrams reveals the existence of a box singularity. Dalitz plots and invariant mass distributions of two charmed mesons from the box diagram for the processes $e^{+}{e}^{-}\to D_s^{-}{D}^{\ast 0}{K}^{+}$ and $D_s^{\ast -}{D}^0{K}^{+}$ are presented at five energy points $\sqrt{s}=4.628,4.641,4.661,4.681$, and $4.698$ GeV. It is found that these box diagrams can generate peaks similar to those observed in experiments, suggesting that the peak of $Z_{cs}(3985)$ may be attributed to the box singularity contribution. Additionally, slight differences in the invariant mass spectra of $D_s^{-}{D}^{\ast 0}$ and $D_s^{\ast -}{D}^0{K}^{+}$ are identified based on the box diagrams, needing further experimental validation.

10 pages, 9 figures, Comments welcome