We present the first lattice QCD determination of the Λb→Λ∗(1520) vector, axial vector, and tensor form factors that are relevant for the rare decays Λb→Λ∗(1520)ℓ+ℓ-. The lattice calculation is performed in the Λ∗(1520) rest frame with nonzero Λb momenta, and is limited to the high-q2 region. An interpolating field with covariant derivatives is used to obtain good overlap with the Λ∗(1520). The analysis treats the Λ∗(1520) as a stable particle, which is expected to be a reasonable approximation for this narrow resonance. A domain-wall action is used for the light and strange quarks, while the b quark is implemented with an anisotropic clover action with coefficients tuned to produce the correct Bs kinetic mass, rest mass, and hyperfine splitting. We use three different ensembles of lattice gauge-field configurations generated by the RBC and UKQCD collaborations, and perform extrapolations of the form factors to the continuum limit and physical pion mass. We give Standard-Model predictions for the Λb→Λ∗(1520)ℓ+ℓ- differential branching fraction and angular observables in the high-q2 region.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)