Measurement of the $B^{pm}$ production asymmetry and the $CP$ asymmetry in $B^{pm} to J/psi K^{pm}$ decays

The $B^{pm}$ meson production asymmetry in $pp$ collisions is measured using $B^+ to bar{D}^0 pi^+$ decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at centre-of-mass energies of $sqrt{s}=$ 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range $2 < p_{rm T} < 30$ GeV/$c$, and rapidities in the range $2.1 < y < 4.5$, are measured to be begin{align*} mathcal{A}_{rm prod}(B^+,sqrt{s}=7~{rm TeV}) &= (-0.41 pm 0.49 pm 0.10) times 10^{-2}, mathcal{A}_{rm prod}(B^+,sqrt{s}=8~{rm TeV}) &= (-0.53 pm 0.31 pm 0.10) times 10^{-2}, end{align*} where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of $B^{+} to J/psi K^{+}$ decays, thus allowing a measurement of the $CP$ asymmetry, begin{equation*} mathcal{A}_{CP} = (0.09 pm 0.27 pm 0.07) times 10^{-2}. end{equation*}