Λ c → N form factors from lattice QCD and phenomenology of Λ c → n ℓ + ν ℓ and Λ c → p μ + μ - decays

A lattice QCD determination of the Λc→N vector, axial vector, and tensor form factors is reported. The calculation was performed with 2+1 flavors of domain-wall fermions at lattice spacings of a≈0.11 and 0.085 fm and pion masses in the range 230 MeVmπ 350 MeV. The form factors are extrapolated to the continuum limit and the physical pion mass using modified z expansions. The rates of the charged-current decays Λc→ne+νe and Λc→nμ+νμ are predicted to be (0.405±0.016stat±0.020syst)|Vcd|2 ps-1 and (0.396±0.016stat±0.020syst)|Vcd|2 ps-1, respectively. The phenomenology of the rare charm decay Λc→pμ+μ- is also studied. The differential branching fraction, the fraction of longitudinally polarized dimuons, and the forward-backward asymmetry are calculated in the standard model and in an illustrative new-physics scenario.