Measurements of the rare decays B -> Kl+l- and B -> K*l+l-

TL;DR

This paper reports precise measurements of rare B meson decays to K and K* mesons with lepton pairs, providing insights into flavor-changing neutral currents and testing the Standard Model predictions.

Contribution

The study presents the first detailed measurements of branching fractions and CP asymmetries for B -> K(*)l+l- decays using a large data sample from BaBar.

Findings

Branching fraction for B -> Kl+l- is (0.34 +- 0.07 +- 0.03) x 10^-6.

Branching fraction for B -> K*l+l- is (0.78^{+0.19}_{-0.17} +- 0.12) x 10^-6.

Measured CP asymmetries and lepton flavor ratios consistent with Standard Model expectations.

Abstract

We present measurements of the flavor-changing neutral current decays B -> Kl+l- and B -> K*l+l-, where l+l- is either an e+e- or mu+mu- pair. The data sample comprises 229 X 10^6 Y(4S) -> BBbar decays collected with the BaBar detector at the PEP-II e+e- storage ring. We measure the branching fractions BF(B -> Kl+l-) = (0.34 +- 0.07 +- 0.03) X 10^-6 and BF(B -> K*l+l-) = (0.78^{+0.19}_{-0.17} +/- 0.12) X 10^-6, the direct CP asymmetries of these decays, and the relative abundances of decays to electrons and muons.