$Ξ$ 𝑐 → $Ξ$ form factors from lattice QCD with domain-wall quarks: A new piece in the puzzle of $Ξ^0_𝑐$ decay rates
We present a lattice quantum chromodynamics (QCD) determination of the vector and axial-vector form factors that describe the charm-baryon semileptonic decays Ξ 𝑐 → Ξℓ + 𝜈 ℓ . The calculation uses a domain-wall action for the up, down, and strange quarks, and an anisotropic clover action for the charm quark. We use four ensembles of gauge-field configurations generated by the RBC and UKQCD collaborations, with lattice spacings between 0.111 and 0.073 fm and pion masses ranging from 420 to 230 MeV. We present Standard Model predictions for the decay rates and branching fractions of Ξ$^0_𝑐$ → Ξ$^−_𝑐$ℓ + 𝜈 ℓ and Ξ$^+_𝑐$ → Ξ$^0_𝑐$ℓ + 𝜈 ℓ for ℓ =𝑒, 𝜇. In particular, we obtain Γ(Ξ$^0_𝑐$ → Ξ − 𝑒 + 𝜈 𝑒 )/|𝑉 𝑐𝑠 | 2 = 0.2515(73) ps −1 and ℬ(Ξ$^0_𝑐$ → Ξ − 𝑒 + 𝜈 𝑒 ) = 3.58(12)%. These values are higher than those predicted by a previous lattice calculation and substantially higher than the experimentally measured values, but consistent with expectations from approximate 𝑆𝑈(3) flavor symmetry.