First observation of top quark production in the forward region

Abstract

Top quark production in the forward region in proton-proton collisions is observed for the first time. The $W+b$ final state with $W\to \hat{I}¼\hat{I}½$ is reconstructed using muons with a transverse momentum, $p_{\mathrm{T}}$, larger than 25 GeV in the pseudorapidity range $2.0<\hat{I}\cdot <4.5$. The $b$ jets are required to have $50<p_{\mathrm{T}}<100$ GeV and $2.2<\hat{I}\cdot <4.2$, while the transverse component of the sum of the muon and $b$-jet momenta must satisfy $p_{\mathrm{T}}>20$ 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 $\ddot{I}ƒ(\mathrm{top})[7\mathrm{TeV}]=239\pm 53(\mathrm{stat})\pm 33(\mathrm{syst})\pm 24(\mathrm{theory})\mathrm{fb}$ and $\ddot{I}ƒ(\mathrm{top})[8\mathrm{TeV}]=289\pm 43(\mathrm{stat})\pm 40(\mathrm{syst})\pm 29(\mathrm{theory})\mathrm{fb}$. These results, along with the observed differential yields and charge asymmetries, are in agreement with next-to-leading order Standard Model predictions.