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

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 $f{b}^{-1}$. The total production cross-sections of top and antitop quarks are also determined. Measurements are performed using the $\mu +b\text{-jet}$ final state within a fiducial region defined by a $b\text{-jet}$ $p_{\text{T, jet}}>50$ GeV and pseudorapidity $2.2<{\eta }_{\text{jet}}<4.0$, with the muon from the $W$-boson decay required to have $p_{\text{T},\mu }>25$ GeV and pseudorapidity $2.0<{\eta }_{\mu }<4.5$. The muon and $b$-jet system must satisfy $p_T(\mu +\text{jet})>20$ GeV. The measured integrated production cross-sections for the top and antitop quarks are ${\sigma }_t=0.95\pm 0.04\pm 0.08\pm 0.02$ pb, ${\sigma }_{\bar{t}}=0.81\pm 0.03\pm 0.07\pm 0.02$ 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.