Measurement of the charge asymmetry in $B^{\pm}\rightarrow ϕK^{\pm}$ and search for $B^{\pm}\rightarrow ϕπ^{\pm}$ decays

Abstract

The \CP-violating charge asymmetry in $B^{\pm}\rightarrow ϕK^{\pm}$ 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 $\mathcal{A}_{CP}(B^{\pm}\rightarrow ϕK^{\pm}) = \rm 0.022\pm 0.021 \pm 0.009$, where the first uncertainty is statistical and the second systematic. In addition, a search for the $B^{\pm}\rightarrow ϕπ^{\pm}$ decay mode is performed, using the $B^{\pm}\rightarrow ϕK^{\pm}$ decay rate for normalization. An upper limit on the branching fraction $\mathcal{B}(B^{\pm}\rightarrow ϕπ^{\pm})< 1.5\times 10^{-7}$ is set at 90% confidence level.