Measurement of the Electroweak Penguin Process B --> X(s) l+ l-

TL;DR

This paper reports the first measurement of the inclusive decay B --> X(s) l+ l-, providing a key test of the Standard Model's predictions for rare electroweak processes involving B mesons.

Contribution

The study presents the first experimental measurement of the branching fraction for B --> X(s) l+ l- decay, using a large data sample collected at Belle.

Findings

Measured branching fraction: (6.1 +/- 1.4 (stat) +1.4-1.1 (syst)) x 10^-6

Analysis used 65.4 million B meson pairs

Results are consistent with Standard Model predictions

Abstract

We report the first measurement of the branching fraction for the inclusive decay B --> X(s) l+ l-, where l is either an electron or a muon and X(s) is a hadronic recoil system that contains an s-quark. We analyzed a data sample of 65.4 * 10**6 B meson pairs collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. We find Br(B --> X(s) l+ l-) = (6.1 +/-1.4(stat) +1.4-1.1(syst)) * 10**(-6) for dilepton masses greater than 0.2 GeV/c**2.