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

Abstract

We measure the total branching fraction of the flavor-changing neutral-current process B→X_sℓ^+ℓ^−, along with partial branching fractions in bins of dilepton and hadronic system (Xs) mass, using a sample of 471×10^6 Υ(4S)→BB 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_sℓ^+ℓ^−)=[6.73^(+0.70)_(−0.64)(stat)^(+0.34)_(−0.25)(exp syst)±0.50(model syst)]×10^(−6) for m^2_(ℓ^+ℓ^−)>0.1  GeV^2/c^4. 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.

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