Evidence for a Neutral Near-Threshold Structure in the KS0 Recoil-Mass Spectra in e+e- → KS0Ds+D*- and e+e- → KS0Ds*+D-

We study the processes e(+)e(-) -> (KSDs+D)-D-0*(-) and e(+)e(-) -> (KSDs)-D-0*D-+(-) as well as their charge conjugated processes, at five center-of-mass energies between 4.628 and 4.699 GeV, using data samples corresponding to an integrated luminosity of 3.8 fb(-1) collected by the BESIII detector at the BEPCII storage ring. Based on a partial reconstruction technique, we find evidence of a structure near the thresholds for Ds+D*- and D-s*(+) D- production in the K-S(0) recoil-mass spectrum, which we refer to as the Z(cs) (3985)(0). Fitting with a Breit-Wigner line shape, we find the mass of the structure to be (3992.2 +/- 1.7 +/- 1.6) MeV/c(2) and the width to be (7.7(-3.8)(+4.1) +/- 4.3) MeV, where the first uncertainties are statistical and the second are systematic. The significance of the Z(cs)(3985)(0) signal is found to be 4.6s including both the statistical and systematic uncertainty. We report the Born cross section multiplied by the branching fraction at different energy points. The mass of the Z(cs) (3985)(0) is close to that of the Z(cs)(3985)(+). Assuming SU(3) symmetry, the cross section of the neutral channel is consistent with that of the charged one. Hence, we conclude that the Z(cs) (3985)(0) is the isospin partner of the Z(cs)(3985)(+).

Automated summary

We studied the e(+)e(-) -> (KSDs+D)-D-0*(-) and e(+)e(-) -> (KSDs)-D-0*D-+(-) processes and their charge conjugated processes at five different center-of-mass energies. By analyzing the data, we found a structure near the thresholds for Ds+D*- and D-s*(+) D- production in the K-S(0) recoil-mass spectrum, which we refer to as the Z(cs) (3985)(0). The mass of the Z(cs) (3985)(0) is close to that of the Z(cs)(3985)(+) and it is considered as the isospin partner of the Z(cs)(3985)(+).