Measurement of the $C\P$ asymmetry in $B^+ \rightarrow K^+ \mu^+ \mu^-$ decays

TL;DR

This paper reports a precise measurement of the charge-parity asymmetry in B+ decays to K+ mu+ mu-, using LHCb data, finding results consistent with the Standard Model and improving the understanding of CP violation in rare B decays.

Contribution

First measurement of CP asymmetry in B+ to K+ mu+ mu- decays across multiple invariant mass bins using LHCb data, with corrections for production and detection asymmetries.

Findings

CP asymmetry consistent with zero within uncertainties

Measurement precision improves constraints on new physics

Results align with Standard Model predictions

Abstract

A measurement of the $C\P$ asymmetry in $B^+ \rightarrow K^+ \mu^+ \mu^-$ decays is presented using $pp$ collision data, corresponding to an integrated luminosity of 1.0${\,fb}^{-1}$, recorded by the LHCb experiment during 2011 at a centre-of-mass energy of 7 TeV. The measurement is performed in seven bins of $\mu^+ \mu^-$ invariant mass squared in the range ${0.05<q^{2}<22.00{\mathrm{GeV^2/}c^4}}$, excluding the ${J/\psi}$ and $\psi{(2S)}$ resonance regions. Production and detection asymmetries are corrected for using the $B^+ \rightarrow J/\psi K^+$ decay as a control mode. Averaged over all the bins, the $C\P$ asymmetry is found to be ${{\cal A}_{C\P} = 0.000\pm 0.033{(stat.)} \pm0.005 {(syst.)} \pm 0.007{}(J/\psi K^+)}$, where the third uncertainty is due to the $C\P$ asymmetry of the control mode. This is consistent with the Standard Model prediction.