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

Abstract

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