First measurement of the charge asymmetry in beauty-quark pair production at a hadron collider

The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in $bbar{b}$ pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0fb$^{-1}$ collected at 7TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the $bbar{b}$ system. The results obtained are: begin{eqnarray} A_{C}^{bbar{b}}(40 < M_{bbar{b}} < 75,rm{GeV/c^2}) &=& 0.4 pm 0.4(rm{stat}) pm 0.3(rm{syst})% ewline A_{C}^{bbar{b}}(75 < M_{bbar{b}} < 105,rm{GeV/c^2}) &=& 2.0 pm 0.9(rm{stat}) pm 0.6(rm{syst})% ewline A_{C}^{bbar{b}}(M_{bbar{b}} > 105,rm{GeV/c^2}) &=&1.6 pm 1.7(rm{stat}) pm 0.6(rm{syst})% end{eqnarray} where $A_{C}^{bbar{b}}$ is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark. The beauty jets are required to satisfy $2<eta<4$, $E_{rm T} > 20$GeV, and have an opening angle in the transverse plane $Deltaphi>2.6$rad. These measurements are consistent with the predictions of the Standard Model.