First observation of top quark production in the forward region

Top quark production in the forward region in proton-proton collisions is observed for the first time. The $W\text{\hspace{0.17em}⁣}+\text{\hspace{0.17em}⁣}b$ final state with $W\to \mu \nu$ is reconstructed using muons with a transverse momentum, $p_{\mathrm{T}}$, larger than 25 GeV in the pseudorapidity range $2.0<\eta <4.5$. The $b$ jets are required to have $50<p_{\mathrm{T}}<100$ GeV and $2.2<\eta <4.2$, while the transverse component of the sum of the muon and $b$-jet momenta must satisfy $p_{\rm T} > 20$ GeV. The results are based on data corresponding to integrated luminosities of 1.0 and $2.0$ fb${}^{-1}$ collected at center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross-sections in the fiducial region are $\sigma({\rm top})[7\rm{TeV}] = 239\pm53({\rm stat})\pm33({\rm syst})\pm24({\rm theory}),{\rm fb}$and$\sigma({\rm top})[8\rm{TeV}] = 289\pm43({\rm stat})\pm40({\rm syst})\pm29({\rm theory}),{\rm fb}$. These results, along with the observed differential yields and charge asymmetries, are in agreement with next-to-leading order Standard Model predictions.