Measurement of the B 0 → K ∗0 e + e − branching fraction at low dilepton mass

Abstract

The branching fraction of the rare decay B 0 → 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 B 0 → J/ψ (e + e −)K ∗0 is utilized as a normalization channel. The branching fraction B(B0→K∗0e+e−)

is measured to be $ \mathcal{B}{{\left( {{B^0}\to {K^{*0 }}{e^{+}}{e^{-}}} \right)}^{{30-1000\,{{\mathrm{MeV}} \left/ {{{c^2}}} \right.}}}}=\left( {3.1_{-0.8}^{+0.9 }{\,}_{-0.3}^{+0.2}\pm 0.2} \right)\times {10^{-7 }}, $

where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B 0 → J/ψ K ∗0 and J/ψ → e + e − branching fractions.