First test of lepton flavor universality in the charmed baryon decays Ω 0 c → Ω − ℓ + ν ℓ using data of the Belle experiment

Abstract

We present the first observation of the Ω 0 c → Ω − μ + ν μ decay and present measurements of the branching fraction ratios of the Ω 0 c → Ω − ℓ + ν ℓ decays compared to the reference mode Ω 0 c → 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 Ω 0 c signal yields are extracted by fitting M Ω ℓ and M Ω π spectra. The branching fraction ratios B ( Ω 0 c → Ω − e + ν e ) / B ( Ω 0 c → Ω − π + ) and B ( Ω 0 c → Ω − μ + ν μ ) / B ( Ω 0 c → 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 ( Ω 0 c → Ω − e + ν e ) / B ( Ω 0 c → Ω − μ + ν μ ) is measured to be 1.02 ± 0.10 ( stat ) ± 0.02 ( syst ) , which is consistent with the expectation of lepton flavor universality.