Observation of a Near-Threshold Structure in the 𝐾+ Recoil-Mass Spectra in 𝑒+⁢𝑒−→𝐾+⁢(𝐷−𝑠⁢𝐷*0+𝐷*− 𝑠⁢𝐷0)

We report a study of the processes of 𝑒+⁢𝑒− →𝐾+⁢𝐷− 𝑠⁢𝐷*0 and 𝐾+⁢𝐷*−𝑠⁢𝐷0 based on 𝑒+⁢𝑒− annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7  fb−1. An excess of events over the known contributions of the conventional charmed mesons is observed near the 𝐷−𝑠⁢𝐷*0 and 𝐷*−𝑠⁢𝐷0 mass thresholds in the 𝐾+ recoil-mass spectrum for events collected at √𝑠 =4.681  GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8 −2.6±2.1)  MeV/𝑐2 and (12.8+5.3 −4.4 ±3.0)  MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3  𝜎 over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into 𝐷− 𝑠⁢𝐷*0 and 𝐷*− 𝑠⁢𝐷0. However, the properties of the excess need further exploration with more statistics.