Test of lepton universality using $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays

Abstract

A measurement of the ratio of the branching fractions of the $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ and $B^{+}\to K^{+}{e}^{+}{e}^{-}$ decays is presented using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb${}^{-1}$, recorded with the LHCb experiment at center-of-mass energies of 7 and 8 $\mathrm{Te}\mathrm{V}$. The value of the ratio of branching fractions for the dilepton invariant mass squared range $1<q^2<6\mathrm{Ge}{\mathrm{V}}^2/c^4$ is measured to be $0.745_{-0.074}^{+0.090}(\mathrm{stat})\pm 0.036(\mathrm{syst})$. This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the SM prediction within $2.6$ standard deviations.

10 pages, 2 figures

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