Measurement of the B → X[subscript s]ℓ[superscript +]ℓ[superscript −] 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[subscript s]ℓ[superscript +]ℓ[superscript −], along with partial branching fractions in bins of dilepton and hadronic system (X[subscript s]) mass, using a sample of 471 × 10[superscript 6] Υ(4S) → B[bar over B] 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[subscript s] final states. Extrapolating from a sum over these exclusive modes, we measure a lepton-flavor-averaged inclusive branching fraction B(B → X[subscript s]ℓ[superscript +]ℓ[superscript −]) = [6.73[+0.70 over −0.64](stat)[+0.34 over −0.25](exp syst) ± 0.50(model syst)] × 10[superscript −6] for m[2 over ℓ+ℓ−] > 0.1 GeV[superscript 2]/c[superscript 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[subscript CP] in bins of dilepton mass; over the full dilepton mass range, we find A[subscript CP] = 0.04 ± 0.11 ± 0.01 for a lepton-flavor-averaged sample.