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First observation of top quark production in the forward region

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Abstract

Top quark production in the forward region in proton-proton collisions is observed for the first time. The $W + b$ final state with $W\to\mu\nu$ is reconstructed using muons with a transverse momentum, $p_{\rm T}$, larger than 25 GeV in the pseudorapidity range $2.0<\eta<4.5$. The $b$ jets are required to have $50 < p_{\rm T} < 100$ 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.

Figures and captions

Distribution of $ p_{\rm T}$ (\mu)/ $p_{\rm T} (j_\mu)$ with fit overlaid for all $W+$jet candidates.

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Results for the inclusive $W+$jet yield (left) and charge asymmetry (right) versus $ p_{\rm T} (\mu+j)$ compared to SM predictions at NLO obtained using MCFM. The data error bars are smaller than the marker size, the SM uncertainties are highly correlated across $ p_{\rm T} (\mu+j)$ bins.

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Results for $ W + c$ compared to SM predictions at NLO obtained using MCFM.

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Distribution of $ p_{\rm T}$ (\mu)/ $p_{\rm T} (j_\mu)$ with fit overlaid for all $ W + b$ candidates.

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Results for the $ W + b$ yield (left) and charge asymmetry (right) versus $ p_{\rm T} (\mu+b)$ compared to SM predictions obtained at NLO using MCFM.

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Distribution of $p_{\rm T}(\mu)/p_{\rm T}(j_{\mu})$ with fit overlaid for all $W + c$ candidates.

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Tables and captions

Relative systematic uncertainties. The symbol $\dagger$ denotes an uncertainty that only applies to the cross-section measurement and not the significance determination. Only the luminosity uncertainty depends on $\sqrt{s}$: 2% at 7 TeV and 1% at 8 TeV.

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Created on 19 October 2019.