Measurement of the $\bar{B}^0-B^0$ and $\bar{B}^0_s-B^0_s$ production asymmetries in $pp$ collisions at $\sqrt{s}=7$ TeV

The $\bar{B}^0-B^0$ and $\bar{B}^0_s-B^0_s$ production asymmetries, $A_\mathrm{P}(B^0)$ and $A_\mathrm{P}(B^0_s)$, are measured by means of a time-dependent analysis of $B^0 \to J/\psi K^{*0}$, $B^0 \to D^- \pi^+$ and $B^0_s \to D_s^- \pi^+$ decays, using a data sample corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by LHCb in $pp$ collisions at a centre-of-mass energy of 7 TeV. The measurements are performed as a function of transverse momentum and pseudorapidity of the $B^0$ and $B^0_s$ mesons within the LHCb acceptance. The production asymmetries, integrated over $p_\mathrm{T}$ and $\eta$ in the range $4 < p_\mathrm{T} < 30$ GeV/c and $2.5<\eta<4.5$, are determined to be $A_\mathrm{P}(B^0) = (-0.35 \pm 0.76 \pm 0.28)\%$ and $A_\mathrm{P}(B^0_s) = (1.09 \pm 2.61 \pm 0.66)\%$, where the first uncertainties are statistical and the second systematic.