We present evidence for the flavor-changing neutral current decay B→K*ℓ+ℓ- and a measurement of the branching fraction for the related process B→Kℓ+ℓ-, where ℓ+ℓ- is either an e+e- or a μ+μ- pair. These decays are highly suppressed in the standard model, and they are sensitive to contributions from new particles in the intermediate state. The data sample comprises 123×10^6 Υ(4S)→BB̅ decays collected with the BABAR detector at the SLAC PEP-II e+e- storage ring. Averaging over K(*) isospin and lepton flavor, we obtain the branching fractions B(B→Kℓ+ℓ-)=(0.65-0.13+0.14±0.04)×10-6 and B(B→K*ℓ+ℓ-)=(0.88-0.29+0.33±0.10)×10-6, where the uncertainties are statistical and systematic, respectively. The significance of the B→Kℓ+ℓ- signal is over 8σ, while for B→K*ℓ+ℓ- it is 3.3σ.

Evidence for the Rare Decay B→K*ℓ+ℓ- and Measurement of the B→Kℓ+ℓ- Branching Fraction

MARGONI, MARTINO;SIMONETTO, FRANCO;STROILI, ROBERTO;SIMI, GABRIELE;
2003

Abstract

We present evidence for the flavor-changing neutral current decay B→K*ℓ+ℓ- and a measurement of the branching fraction for the related process B→Kℓ+ℓ-, where ℓ+ℓ- is either an e+e- or a μ+μ- pair. These decays are highly suppressed in the standard model, and they are sensitive to contributions from new particles in the intermediate state. The data sample comprises 123×10^6 Υ(4S)→BB̅ decays collected with the BABAR detector at the SLAC PEP-II e+e- storage ring. Averaging over K(*) isospin and lepton flavor, we obtain the branching fractions B(B→Kℓ+ℓ-)=(0.65-0.13+0.14±0.04)×10-6 and B(B→K*ℓ+ℓ-)=(0.88-0.29+0.33±0.10)×10-6, where the uncertainties are statistical and systematic, respectively. The significance of the B→Kℓ+ℓ- signal is over 8σ, while for B→K*ℓ+ℓ- it is 3.3σ.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2463084
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