Search for the Rare Decays B --> Kl^+l^- and B --> K^*l^+l^-

TL;DR

This paper reports a search for rare B meson decays involving flavor-changing neutral currents, setting upper limits close to Standard Model predictions using data from the BABAR detector at the PEP-II B Factory.

Contribution

First search for these specific rare decays with new upper limits close to theoretical expectations, using a large dataset from the BABAR experiment.

Findings

Upper limit for B→Kℓ+ℓ− decay: < 0.50×10⁻⁶

Upper limit for B→K*ℓ+ℓ− decay: < 2.9×10⁻⁶

No evidence for lepton-flavor-violating decays found

Abstract

We present results from a search for the flavor-changing neutral current decays $B\to K\ell^+\ell^-$ and $B\to K^*\ell^+\ell^-$, where $\ell^+\ell^-$ is either an $e^+e^-$ or $\mu^+\mu^-$ pair. The data sample comprises $22.7\times 10^6$ $\Upsilon(4S)\to B\bar B$ decays collected with the BABAR detector at the PEP-II $B$ Factory. We obtain the 90% C.L. upper limits ${\mathcal B}(B\to K\ell^+\ell^-)< 0.50\times 10^{-6}$ and ${\mathcal B}(B\to K^*\ell^+\ell^-)<2.9\times 10^{-6}$, close to Standard Model predictions for these branching fractions. We have also obtained limits on the lepton-family-violating decays $B\to Ke^{\pm}\mu^{\mp}$ and $B\to K^{*}e^{\pm}\mu^{\mp}$.