First test of lepton flavor universality in the charmed baryon decays Ω$^{0}$$_{c}$ → Ω$^{-}$ℓ$^{+}$ν$_{ℓ}$ using data of the Belle experiment

We present the first observation of the Ω0c→Ω−μ+νμ decay and present measurements of the branching fraction ratios of the Ω0c→Ω−ℓ+νℓ decays compared to the reference mode Ω0c→Ω−π+, (ℓ=e or μ). 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 Ω0c signal yields are extracted by fitting MΩℓ and MΩπ spectra. The branching fraction ratios B(Ω0c→Ω−e+νe)/B(Ω0c→Ω−π+) and B(Ω0c→Ω−μ+νμ)/B(Ω0c→Ω−π+) are measured to be 1.98±0.13(stat)±0.08(syst) and 1.94±0.18(stat)±0.10(syst), respectively. The ratio of B(Ω0c→Ω−e+νe)/B(Ω0c→Ω−μ+νμ) is measured to be 1.02±0.10(stat)±0.02(syst), which is consistent with the expectation of lepton flavor universality.