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Measurements of the branching fractions of the semileptonic decays $$Xi_{c}^{0} to Xi^{-} ell^{+} nu_{ell}$$ and the asymmetry parameter of $$Xi_{c}^{0} to Xi^{-} pi^{+}$$

Li, Y. B.*; Tanida, Kiyoshi   ; Belle Collaboration*; 182 of others*

Using data samples of 89.5 and 711 fb$$^{-1}$$ recorded at energies of $$sqrt{s}=10.52$$ and $$10.58$$ GeV, respectively, with the Belle detector at the KEKB $$e^+e^-$$ collider, we report measurements of branching fractions of semileptonic decays $$Xi_{c}^{0} to Xi^{-} ell^{+} nu_{ell}$$ ($$ell=e$$ or $$mu$$) and the $$CP$$-asymmetry parameter of $$Xi_{c}^{0} to Xi^{-} pi^{+}$$ decay. The branching fractions are measured to be $${cal B}(Xi_{c}^{0} to Xi^{-} e^{+} nu_{e}$$)=($$1.31 pm 0.04 pm 0.07 pm 0.38$$)% and $${cal B}(Xi_{c}^{0} to Xi^{-} mu^{+} nu_{mu}$$)=($$1.27 pm 0.06 pm 0.10 pm 0.37$$)%, and the decay parameter $$alpha_{Xipi}$$ is measured to be $$0.63 pm 0.03 pm 0.01$$ with much improved precision compared to the current world average. The corresponding ratio $${cal B}(Xi_{c}^{0} to Xi^{-} e^{+} nu_{e})$$/$${cal B}(Xi_{c}^{0} to Xi^{-} mu^{+} nu_{mu})$$ is 1.03 $$pm$$ 0.05 $$pm$$ 0.07, which is consistent with the expectation of lepton flavor universality. The first measured asymmetry parameter $${cal A}_{CP} = (alpha_{Xi^{-}pi^{+}} + alpha_{bar{Xi}^{+}pi^{-}})/(alpha_{Xi^{-}pi^{+}} - alpha_{bar{Xi}^{+}pi^{-}}) = 0.024 pm 0.052 pm 0.014$$ is found to be consistent with zero. The first and the second uncertainties above are statistical and systematic, respectively, while the third ones arise due to the uncertainty of the $$Xi_{c}^{0} to Xi^{-} pi^+$$ branching fraction.



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Category:Physics, Multidisciplinary



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