We present a model-independent bound on R(J/ψ)≡ℬℛ(BC+→J/ψτ+ντ)/ℬℛ(BC+→J/ψµ+νµ). This bound is constructed by constraining the form factors through a combination of dispersive relations, heavy-quark relations at zero-recoil, and the limited existing determinations from lattice QCD. The resulting 95% confidence-level bound, 0.20 ≤ R(J/ψ) ≤ 0.39, agrees with the recent LHCb result at 1.3σ, and rules out some previously suggested model form factors.
- Heavy Quark Physics
- Lattice QCD
- Quark Masses and SM Parameters
ASJC Scopus subject areas
- Nuclear and High Energy Physics