Improved Upper Limits on the FCNC Decays B→ Kℓ⁺ℓ⁻ and B→ K*(892)ℓ⁺ℓ⁻

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We have searched a sample of 9.6 million BBbar events for the flavor-changing neutral current decays B -> K l+ l- and B -> K*(892) l+ l-. We subject the latter decay to the requirement that the dilepton mass exceed 0.5 GeV. There is no indication of a signal. We obtain the 90% confidence level upper limits on the branching fractions Br(B -> K l+ l-) < 1.7 × 10⁻⁶ and Br(B -> K*(892) l+ l-) < 3.3 × 10⁻⁶. We also obtain an upper limit on the weighted average 0.65 Br(B -> K l+ l-) + 0.35 Br(B -> K*(892) l+ l-) < 1.5 × 10⁻⁶. The weighted-average limit is only 50% above the Standard Model prediction.