Simultaneous explanation of the RK and R (D (*)) puzzles

At present, there are several hints of lepton flavor non-universality. The LHCb Collaboration has measured R_K ≡ B (B⁺ →K⁺μ⁺μ^-) / B (B⁺ →K⁺e⁺e^-), and the BaBar Collaboration has measured R (^{D (*)}) ≡ B (B bar →^{D (*) +}τ^-ν_barτ) / B (B bar →^{D (*) +}ℓ^-ν_barℓ) (ℓ = e , μ). In all cases, the experimental results differ from the standard model predictions by 2- 3 σ. Recently, an explanation of the R_K 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.