First test of Lepton Flavor Universality in the charmed baryon decays ${\Omega }_c^0\to {\Omega }^{-}{\ell }^{+}{\nu }_{\ell }$ using data of the Belle experiment

Abstract

We present the first observation of the ${\Omega }_c^0\to {\Omega }^{-}{\mu }^{+}{\nu }_{\mu }$ decay and present measurements of the branching fraction ratios of the ${\Omega }_c^0\to {\Omega }^{-}{\ell }^{+}{\nu }_{\ell }$ decays compared to the reference mode ${\Omega }_c^0\to {\Omega }^{-}{\pi }^{+}$, ($\ell =e$ or $\mu$). This analysis is based on 89.5 fb${}^{-1}$, 711 fb${}^{-1}$, and 121.1 fb${}^{-1}$ data samples collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider at the center-of-mass energies of 10.52 GeV, 10.58 GeV, and 10.86 GeV, respectively. The ${\Omega }_c^0$ signal yields are extracted by fitting $M_{{\Omega }^{-}{\ell }^{+}}$ and $M_{{\Omega }^{-}{\pi }^{+}}$ spectra. The branching fraction ratios $\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{e}^{+}{\nu }_e)/\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\pi }^{+})$ and $\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\mu }^{+}{\nu }_{\mu })/\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\pi }^{+})$ are measured to be $1.98\pm 0.13(stat.)\pm 0.08(syst.)$ and $1.94\pm 0.18(stat.)\pm 0.10(syst.)$, respectively. The ratio of $\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{e}^{+}{\nu }_e)/\mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\mu }^{+}{\nu }_{\mu })$ is measured to be $1.02\pm 0.10(stat.)\pm 0.02(syst.)$, which is consistent with the expectation of lepton flavor universality.

Comments: 7 pages, 3 figures, accepted for publication as a Letter in Physical Review D