Measurement of the B → X₋s ℓ⁺ℓ⁻ Branching Fraction and Search for Direct CP Violation from a Sum of Exclusive Final States


We measure the total branching fraction of the flavor-changing neutral-current process B→X_s ℓ⁺ℓ⁻, along with partial branching fractions in bins of dilepton and hadronic system (X_s) mass, using a sample of 471 x 10⁶ ϒ(4S) → BB̅ events recorded with the BABAR detector. The admixture of charged and neutral B mesons produced at PEP-II2 are reconstructed by combining a dilepton pair with 10 different X_s final states. Extrapolating from a sum over these exclusive modes, we measure a lepton-flavor-averaged inclusive branching fraction ℬ(B→X_s ℓ⁺ℓ⁻) = [6.73_{-0.64}^{+0.70}(stat){-0.25}^{+0.34}(exp syst) ± 0.50(model syst)] x 10⁻⁶ for m{ℓ⁺ℓ⁻}^2 > 0.1 GeV²/c⁴. Restricting our analysis exclusively to final states from which a decaying B meson's flavor can be inferred, we additionally report measurements of the direct CP asymmetry A_{CP} in bins of dilepton mass; over the full dilepton mass range, we find A_{CP} = 0.04 ± 0.11 ± 0.01 for a lepton-flavor-averaged sample.


Supplemental materials available at:


Branching fractions (Nuclear physics), B mesons, CP violation (Nuclear physics), Dileptons, Hadrons


©2014 American Physical Society