Search for hidden-charm tetraquark with strangeness in e+e-→K+ D*+s D*0 + c.c.*

We report a search for a heavier partner of the recently observed state, denoted as , in the process , based on collision data collected at the center-of-mass energies of , 4.682 and 4.699 GeV with the BESIII detector. The is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark. A partial-reconstruction technique is used to isolate recoil-mass spectra, which are probed for a potential contribution from . We find an excess of candidates with a significance of , after considering systematic uncertainties, at a mass of . As the data set is limited in size, the upper limits are evaluated at the 90% confidence level on the product of the Born cross sections and the branching fraction of , under different assumptions of the mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies. The upper limits of are found to be at the level of pb at each energy. Larger data samples are needed to confirm the state and clarify its nature in the coming years.