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*}
Categories: hep-ex