Standard model predictions for B→Kℓ+ℓ−with form factors from lattice QCD

Abstract

We calculate, for the first time using unquenched lattice QCD form factors, the standard model differential branching fractions dℬ/dq2(B→Kℓ+ℓ−) for ℓ=e, μ, τ and compare with experimental measurements by Belle, BABAR, CDF, and LHCb. We report on ℬ(B→Kℓ+ℓ−) in q2 bins used by experiment and predict ℬ(B→Kτ+τ−)=(1.41±0.15)×10−7. We also calculate the ratio of branching fractions Rμe=1.00029(69) and predict Rτℓ=1.176(40), for ℓ=e, μ. Finally, we calculate the “flat term” in the angular distribution of the differential decay rate Fe,μ,τH in experimentally motivated q2 bins