Measurement of the charge asymmetry in $B^{\pm }\to \varphi K^{\pm }$ and search for $B^{\pm }\to \varphi {\pi }^{\pm }$ decays

Abstract

The \CP-violating charge asymmetry in $B^{\pm }\to \varphi K^{\pm }$ decays is measured in a sample of $pp$ collisions at 7 TeV centre-of-mass energy, corresponding to an integrated luminosity of 1.0 fb${}^{-1}$ collected by the LHCb experiment. The result is ${\mathcal{A}}_{CP}(B^{\pm }\to \varphi K^{\pm })=0.022\pm 0.021\pm 0.009$, where the first uncertainty is statistical and the second systematic. In addition, a search for the $B^{\pm }\to \varphi {\pi }^{\pm }$ decay mode is performed, using the $B^{\pm }\to \varphi K^{\pm }$ decay rate for normalization. An upper limit on the branching fraction $\mathcal{B}(B^{\pm }\to \varphi {\pi }^{\pm })<1.5\times 10^{-7}$ is set at 90% confidence level.