A new long distance contribution to $B^{\pm }\to K^{\pm }\mathrm{/}{\pi }^{\pm }{\mathrm{\ell }}^{+}\mathrm{\ell }-$ decays

We have identified a missing long-distance (one-photon exchange) contribution to the $B^{\pm }\to K^{\pm }\mathrm{/}{\pi }^{\pm }{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decays. Although it does not help to explain the anomaly measured by the LHCb Coll. in the ratio $R_K = $\mathcal{B}$(B^\pm\to K^\pm\mu^+\mu^-)/$\mathcal{B}$(B^\pm\to K^\pm e^+e^-)\sim0.75$(2.6$\sigma$deviationwithrespectto$R_K=1+$\mathcal{O}$(10^{-4})$ in the Standard Model), it provides a sizable contribution to the branching ratio of the $B^{\pm }\to {\pi }^{\pm }{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decays. The new decay mechanism gives rise to a measurable CP asymmetry, which is of order 1% in both channels. These predictions can be tested in forthcoming LHCb measurements.