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High Energy Physics - Experiment, hep-ex
MPINP:
LHCb - Abteilung Hofmann
Abstract:
The difference in the angular distributions between beauty quarks and
antiquarks, referred to as the charge asymmetry, is measured for the first time
in $b\bar{b}$ 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 $b\bar{b}$ system. The
results obtained are: \begin{eqnarray}
A_{C}^{b\bar{b}}(40 < M_{b\bar{b}} < 75\,\rm{GeV/c^2}) &=& 0.4 \pm
0.4(\rm{stat}) \pm 0.3(\rm{syst})\%\newline
A_{C}^{b\bar{b}}(75 < M_{b\bar{b}} < 105\,\rm{GeV/c^2}) &=& 2.0 \pm
0.9(\rm{stat}) \pm 0.6(\rm{syst})\%\newline
A_{C}^{b\bar{b}}(M_{b\bar{b}} > 105\,\rm{GeV/c^2}) &=&1.6 \pm 1.7(\rm{stat})
\pm 0.6(\rm{syst})\% \end{eqnarray} where $A_{C}^{b\bar{b}}$ 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
$\Delta\phi>2.6$rad. These measurements are consistent with the predictions of
the Standard Model.
