Measurement of the top-quark production cross-section and charge asymmetry at LHCb

Abstract

The first measurements of the top- and antitop-quark differential production cross-sections and the top-quark charge asymmetry in the forward region are presented, using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.4 $fb^{-1}$. The total production cross-sections of top and antitop quarks are also determined. Measurements are performed using the $μ+b\text{-jet}$ final state within a fiducial region defined by a $b\text{-jet}$ $p_{\text{T, jet}}>50$ GeV and pseudorapidity $2.2<η_{\text{jet}}<4.0$,, with the muon from the $W$-boson decay required to have $p_{\text{T},μ}>25$ GeV and pseudorapidity $2.0<η_μ<4.5$. The muon and $b$-jet system must satisfy $p_{T}(μ+\text{jet}) > 20$ GeV. The measured integrated production cross-sections for the top and antitop quarks are $σ_{t} = 0.95 \pm 0.04 \pm 0.08 \pm 0.02$ pb, $σ_{\bar{t}} = 0.81 \pm 0.03 \pm 0.07 \pm 0.02$ pb, where the first uncertainty is statistical, the second systematic, and the third accounts for the luminosity uncertainty. The top-quark charge asymmetry is measured to be $A_C^{t} = 0.08 \pm 0.03 \pm 0.01$, where the first uncertainty is statistical and the second is systematic. These results are consistent with next-to-leading-order Standard Model predictions.