First Evidence of the Decay B^{+}→π^{+}e^{+}e^{-}

The first evidence for the decay B^{+}→π^{+}e^{+}e^{-} is reported using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9  fb^{-1}. A signal excess with a significance of 3.2σ is observed and the branching fraction is measured to be B(B^{+}→π^{+}e^{+}e^{-})=(2.4_{-0.8}^{+0.9} _{-0.2}^{+0.4})×10^{-8}, where the first set of uncertainties is statistical and the second is systematic. The result is consistent with the Standard Model expectation.