Evidence for K→ K *ℓ+ℓ– and measurement of B→ Kℓ+ℓ–

Anders Ryd

doi:10.1140/epjcd/s2003-03-205-3

EPJ

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2024 Impact factor 4.8

Particles and Fields

Open Access

Eur Phys J C (2004) 33: s285-s287
https://doi.org/10.1140/epjcd/s2003-03-205-3

PS02 Rare Decays

Evidence for K→ K ^*ℓ⁺ℓ^– and measurement of B→ Kℓ⁺ℓ^–

Anders Ryd

California Institute of Technology, Pasadena CA 91125,

Received: 5 November 2003
Accepted: 11 December 2003
Published online: 12 December 2003

Abstract

We present evidence for the flavor-changing neutral current decay B→ K ^*ℓ⁺ℓ^– and a measurement of the B→ Kℓ⁺ℓ^– branching fraction, where ℓ⁺ℓ^– is either an e ⁺ e ^– or μ ⁺ μ ^– pair. The data sample analyzed comprises 88.5× 10⁶ $\Upsilon(4S)\to B\bar B$ decays collected with the BABAR detector at the PEP-II e ⁺ e ^– storage ring. Averaging over K ^(*) isospin and lepton flavor, we obtain ${\cal B}(B\to K^*\ell^{+}\ell^{-})= (1.40^{+0.57}_{-0.49}\pm0.21)\times 10^{-6}$ and ${\cal B}(B\to K\ell^{+}\ell^{-})=(0.68^{+0.17}_{-0.15}\pm0.04)\times 10^{-6}$ , where the uncertainties are statistical and systematic. The significance for the B→ K ^*ℓ⁺ℓ^– signal is 3.0σ and for B→ Kℓ⁺ℓ^– the signal significance is over 7σ.