Test of lepton flavor universality in B± → K± μ+μ- and B± → K± e+ e- decays in proton-proton collisions at √s=13 TeV

Abstract

A test of lepton flavor universality in B-+/- -> K +/- mu(+) mu(-) and B-+/- -> (K)+/- e(+) e(-) decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B-+/- -> K-+/- mu(+)mu(-) decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at root s = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions B(B-+/- -> K-+/- mu(+) mu(-)) to B(B-+/- -> K-+/- e(+) e(-)) is determined from the measured double ratio R(K) of these decays to the respective branching fractions of the B-+/- -> J/psi K-+/- with J/psi -> mu(+)mu(-) and e(+) e(-) decays, which allow for significant cancellation of systematic uncertainties. The ratio R(K) is measured in the range 1.1 K-+/- mu(+) mu(-)) = (12.42 +/- 0.68) x 10(-8), is consistent with the present world-average value and has a comparable precision.