Measurement of the B0 → K∗0 e+ e− Branching Fraction at Low Dilepton Mass

The branching fraction of the rare decay B0 → K∗0 e+ e− in the dilepton mass region from 30 to 1000 MeV/c^2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb^−1, at a centre-of-mass energy of 7 TeV. The decay mode B0 → J/ψ(e+ e−) K∗0 is utilized as a normalization channel. The branching fraction B(B0 → K∗0 e+ e−) is measured to be B(B0 → K∗0 e+ e−){30−1000 MeV/c2} = (3.1 {−0.8}{+0.9} {−0.3}{+0.2} ± 0.2) x 10^−7, where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B0 → J/ψ K∗0 and J/ψ → e+ e− branching fractions.