Simultaneous explanation of the R K and R ( D (⁎) ) puzzles

At present, there are several hints of lepton flavor non-universality. The LHCb Collaboration has measured RK≡B(B+→K+μ+μ−)/B(B+→K+e+e−), and the BaBar Collaboration has measured R(D(⁎))≡B(B¯→D(⁎)+τ−ν¯τ)/B(B¯→D(⁎)+ℓ−ν¯ℓ) (ℓ=e,μ). In all cases, the experimental results differ from the standard model predictions by 2–3σ. Recently, an explanation of the RK puzzle was proposed in which new physics (NP) generates a neutral-current operator involving only third-generation particles. Now, assuming the scale of NP is much larger than the weak scale, this NP operator must be made invariant under the full SU(3)C×SU(2)L×U(1)Y gauge group. In this Letter, we note that, when this is done, a new charged-current operator can appear, and this can explain the R(D(⁎)) puzzle. A more precise measurement of the double ratio R(D)/R(D⁎) can rule out this model.