B̄s,d⁰ → J/ψμ+μ− decays in QCD factorization

A bstract Motivated by the first LHCb searches for the rare B̄s,d⁰ B ¯ s , d 0 → J / ψμ + μ − decays, we perform a detailed study of these processes within the QCD factorization formalism. Since the transverse size of the J / ψ meson is small in the heavy quark mass limit, this formalism is generally expected to hold for these decays. We include both the leading- and next-to-leading-order QCD corrections to the hard-scattering kernels, which are convoluted with the light-cone distribution amplitudes (LCDAs) of the initial- and final-state hadrons. It is numerically found that, depending on the model parameters for the leading-twist B -meson LCDA, the maximum branching ratios of B̄ₛ⁰ B ¯ s 0 → J / ψμ + μ − and B̄d⁰ B ¯ d 0 → J / ψμ + μ − , integrated over the dimuon invariant mass squared q 2 from 1 GeV 2 to ( m_Bs,d m B s , d − m J / ψ ) 2 , can reach up to 2.21 × 10 −9 and 7.69 × 10 −11 at the leading order in α s , respectively. After incorporating the non-factorizable one-loop vertex corrections, these branching ratios are further reduced by about one order of magnitude, with B.(B̄ₛ⁰→ J/ψ μ⁺μ⁻)|_q²≥ 1GeV² B B ¯ s 0 → J / ψ μ + μ − q 2 ≥ 1 GeV 2 = 2.88 × 10 −10 and B.(B̄d⁰→ J/ψ μ⁺μ⁻)|_q²≥ 1GeV² B B ¯ d 0 → J / ψ