# Measurement of forward top pair production in the dilepton channel in $pp$ collisions at $\sqrt{s}=13$ TeV

[to restricted-access page]

## Abstract

Forward top quark pair production is studied in $pp$ collisions in the $\mu eb$ final state using a data sample corresponding to an integrated luminosity of 1.93 fb$^{-1}$ collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted $\Delta R$, between the two leptons must be larger than 0.1. The $b$-jet axis is required to be separated from both leptons by a $\Delta R$ of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be $$\sigma_{t\bar{t}}= 126\pm19 (\mathrm{stat})\pm16 (\mathrm{syst})\pm5 (\mathrm{lumi}) \mathrm{ fb}$$ where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.

## Figures and captions

 The muon (left) $\eta$ and (right) $p_{\mathrm{ T}}$ distribution in data compared to the expected contributions. The $t \overline t$ signal yield is determined to be the number of selected events minus the sum of the expected backgrounds. The multiboson background is determined to be negligible. Fig1l.pdf [14 KiB] HiDef png [132 KiB] Thumbnail [128 KiB] Fig1r.pdf [14 KiB] HiDef png [142 KiB] Thumbnail [135 KiB] The electron (left) $\eta$ and (right) $p_{\mathrm{ T}}$ distribution in data compared to the expected contributions. The $t \overline t$ signal yield is determined to be the number of selected events minus the sum of the expected backgrounds. The multiboson background is determined to be negligible. Fig2l.pdf [15 KiB] HiDef png [136 KiB] Thumbnail [130 KiB] Fig2r.pdf [15 KiB] HiDef png [148 KiB] Thumbnail [143 KiB] The $b$ -jet (left) $\eta$ and (right) $p_{\mathrm{ T}}$ distribution in data compared to the expected contributions. The $t \overline t$ signal yield is determined to be the number of selected events minus the sum of the expected backgrounds. The multiboson background is determined to be negligible. Fig3l.pdf [15 KiB] HiDef png [157 KiB] Thumbnail [152 KiB] Fig3r.pdf [15 KiB] HiDef png [151 KiB] Thumbnail [143 KiB] The combined invariant mass of the muon, electron and $b$ -jet in data compared to the expected contributions. The $t \overline t$ signal yield is determined to be the number of selected events minus the sum of the expected backgrounds. The multiboson background is determined to be negligible. Fig4.pdf [15 KiB] HiDef png [158 KiB] Thumbnail [152 KiB] Graphical comparison of the measured cross-sections with the predictions from the aMC@NLO , POWHEG and MCFM generators. For the data, the inner error band represents the statistical uncertainty, and the outer the total, while for the theoretical predictions, the inner band represents the scale uncertainty and the outer represents the total. The prediction is shown (above) for the muon, electron and jet fiducial, and (below) for the top quark fiducial region. Fig5.pdf [14 KiB] HiDef png [108 KiB] Thumbnail [101 KiB] Animated gif made out of all figures. PAPER-2017-050.gif Thumbnail

## Tables and captions

 The efficiency to fully reconstruct and identify the candidates. Table_1.pdf [24 KiB] HiDef png [182 KiB] Thumbnail [81 KiB] tex code Summary of the systematic uncertainties on the measurement of the $t\bar{t}$ cross-section in the fiducial region defined by the requirements placed on the leptons and the $b$ -jet , expressed as a percentage of the measured cross-section. An additional uncertainty due to $t \overline t$ modelling is considered when extrapolating to the top quark fiducial region. Table_2.pdf [16 KiB] HiDef png [225 KiB] Thumbnail [91 KiB] tex code

Created on 17 August 2019.Citation count from INSPIRE on 17 August 2019.