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Register a new userObservation of Excited $Omega_c$ Charmed Baryons in $e^+e^-$ Collisions
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Using the entire Belle data sample of 980 ${rm fb}^{-1}$ of $e^+e^-$ collisions, we present the results of a study of excited $Omega_c$ charmed baryons in the decay mode $Xi_c^+K^-$. We show confirmation of four of the five narrow states reported by the LHCb Collaboration: the $Omega_c(3000)$ , $Omega_c(3050)$, $Omega_c(3066)$, and $Omega_c(3090)$.
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The first observation of the $Omega_b^-toXi_c^+ K^- pi^-$ decay is reported using proton-proton collision data at centre-of-mass energies of $7$, $8$ and $13,mathrm{TeV}$ collected by the LHCb experiment, corresponding to an integrated luminosity of $9,mathrm{fb}^{-1}$. Four excited $Omega_c^0$ baryons are observed in the $Xi_c^+ K^-$ mass projection of the $Omega_b^-toXi_c^+ K^- pi^-$ decays with significance exceeding five standard deviations. Their relative production rates, masses and natural widths are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of $Omega_b^-toXi_c^+ K^- pi^-$ is measured relative to the $Omega_b^-to Omega_c^0 pi^-$ decay mode and a precise measurement of the $Omega_b^-$ mass of $6044.3 pm 1.2 pm 1.1^{,+0.19}_{,-0.22},mathrm{MeV}$ is obtained.
We observe $D^0-bar{D}^0$ mixing in the decay $D^0rightarrow K^+pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x}^2 = (0.09pm0.22)times 10^{-3}$ and $y = (4.6pm3.4)times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53pm0.13)times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.
We measure the inclusive production cross sections of hyperons and charmed baryons from $e^+e^-$ annihilation using a 800 fb$^{-1}$ data sample taken near the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The feed-down contributions from heavy particles are subtracted using our data, and the direct production cross sections are presented for the first time. The production cross sections divided by the number of spin states for $S=-1$ hyperons follow an exponential function with a single slope parameter except for the $Sigma(1385)^+$ resonance. Suppression for $Sigma(1385)^+$ and $Xi(1530)^0$ hyperons is observed. Among the production cross sections of charmed baryons, a factor of three difference for $Lambda_c^+$ states over $Sigma_c$ states is observed. This observation suggests a diquark structure for these baryons.
Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda_b0pi+pi- spectrum with masses 5911.97 +- 0.12(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.77 +- 0.08(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).
Based on a sample of etapr mesons produced in the radiative decay $J/psitogammaeta^{prime}$ in $1.31times 10^9$ $J/psi$ events collected with the BESIII detector, the decay $eta^{prime}toomega e^{+} e^{-}$ is observed for the first time, with a statistical significance of $8sigma$. The branching fraction is measured to be $mathcal{B}(eta^{prime}toomega e^{+} e^{-})=(1.97pm0.34(text{stat})pm0.17(text{syst}))times10^{-4}$, which is in agreement with theoretical predictions. The branching fraction of $eta^{prime}toomegagamma$ is also measured to be $(2.55pm0.03(text{stat})pm0.16(text{syst}))times10^{-2}$, which is the most precise measurement to date, and the relative branching fraction $frac{mathcal{B}(eta^{prime}to omega e^{+}e^{-})}{mathcal{B}(eta^{prime}to omega gamma)}$ is determined to be $(7.71pm1.34(text{stat})pm0.54(text{syst}))times10^{-3}$.
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