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.
Categories: hep-ex