Evidence of a structure in $bar{K}^{0} Lambda_{c}^{+}$ consistent with a charged $Xi_c(2930)^{+}$, and updated measurement of $bar{B}^{0} to bar{K}^{0} Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ at Belle


Abstract in English

We report evidence for the charged charmed-strange baryon $Xi_{c}(2930)^+$ with a signal significance of 3.9$sigma$ with systematic errors included. The charged $Xi_{c}(2930)^+$ is found in its decay to $K_{S}^{0} Lambda_{c}^+$ in the substructure of $bar{B}^{0} to K^{0}_{S} Lambda_{c}^{+} bar{Lambda}_{c}^{-}$ decays. The measured mass and width are $[2942.3 pm 4.4 (rm stat.) pm 1.5(rm syst.)]$~MeV/$c^{2}$ and $[14.8 pm 8.8(rm stat.) pm 2.5(rm syst.)]$~MeV, respectively, and the product branching fraction is $cal{B}(bar{B}^{0} to Xi_c(2930)^{+} bar{Lambda}_{c}^{-}) cal{B}(Xi_c(2930)^{+}to bar{K}^{0} Lambda_{c}^{+})=[2.37 pm 0.51 (rm stat.)pm 0.31(rm syst.)]times 10^{-4}$. We also measure $cal{B}(bar{B}^{0} to bar{K}^{0} Lambda_{c}^{+} bar{Lambda}_{c}^{-}) = [3.99 pm 0.76(rm stat.) pm 0.51(rm syst.)] times 10^{-4}$ with greater precision than previous experiments, and present the results of a search for the charmonium-like state $Y(4660)$ and its spin partner, $Y_{eta}$, in the $Lambda_{c}^{+}bar{Lambda}_{c}^{-}$ invariant mass spectrum. No clear signals of the $Y(4660)$ or $Y_{eta}$ are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $(772pm11)times 10^{6} Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.

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