Test of lepton flavor universality in ${\text{B}}^{\pm }\to {\text{K}}^{\pm }{\mu }^{+}{\mu }^{-}$ and ${\text{B}}^{\pm }\to {\text{K}}^{\pm }{\text{e}}^{+}{\text{e}}^{-}$ decays in proton-proton collisions at $\sqrt{\text{s}}=\text{13}\text{TeV}$

Journal Article · Tue Jul 02 20:00:00 EDT 2024 · Reports on Progress in Physics

DOI:https://doi.org/10.1088/1361-6633/ad4e65· OSTI ID:2396071

CMS Collaboration, The

Abstract

A test of lepton flavor universality in ${\text{B}}^{\pm }\to {\text{K}}^{\pm }{\mu }^{+}{\mu }^{-}$ and ${\text{B}}^{\pm }\to {\text{K}}^{\pm }{\text{e}}^{+}{\text{e}}^{-}$ decays, as well as a measurement of differential and integrated branching fractions of a nonresonant ${\text{B}}^{\pm }\to {\text{K}}^{\pm }{\mu }^{+}{\mu }^{-}$ decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at $\sqrt{s}=13\text{TeV}$ 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 $B({\text{B}}^{\pm }\to {\text{K}}^{\pm }{\mu }^{+}{\mu }^{-})$ to $B({\text{B}}^{\pm }\to {\text{K}}^{\pm }{\text{e}}^{+}{\text{e}}^{-})$ is determined from the measured double ratio $R\left(\text{K}\right)$ of these decays to the respective branching fractions of the ${\text{B}}^{\pm }\to \text{J}/\text{ψ}{\text{K}}^{\pm }$ with $\text{J}/\text{ψ}\to {\mu }^{+}{\mu }^{-}$ and ${\text{e}}^{+}{\text{e}}^{-}$ decays, which allow for significant cancellation of systematic uncertainties. The ratio $R\left(\text{K}\right)$ is measured in the range $1.1<q^2<6.0{\text{GeV}}^2$ , where q is the invariant mass of the lepton pair, and is found to be $R\left(\text{K}\right)={0.78}_{-0.23}^{+0.47}$ , in agreement with the standard model expectation $R\left(\text{K}\right)\approx 1$ . This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same q ² range, $B({\text{B}}^{\pm }\to {\text{K}}^{\pm }{\mu }^{+}{\mu }^{-})=(12.42\pm 0.68)\times {10}^{-8}$ , is consistent with the present world-average value and has a comparable precision.

• Sponsoring Organization: USDOE
• OSTI ID: 2396071
• Alternate ID(s): OSTI ID: 3010753; OSTI ID: 2282622
• Journal Information: Reports on Progress in Physics, Journal Name: Reports on Progress in Physics Journal Issue: 7 Vol. 87; ISSN 0034-4885
• Publisher: IOP Publishing
• Country of Publication: United Kingdom
• Language: English