Measurement of the $t\overline{t}$ production cross section in pp collisions at $\sqrt{s}\mathbf{=}7\mathrm{TeV}$ in dilepton final states containing a $\tau$

The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying $\tau$ lepton from the decay $t\overline{t}\to (\ell {\nu }_{\ell })({\tau }_{\mathrm{h}}{\nu }_{\tau })\mathrm{b}\overline{\mathrm{b}}$, ($\ell =e,\mu$). The data sample corresponds to an integrated luminosity of $2.0{\mathrm{fb}}^{-1}$ for the electron channel and $2.2{\mathrm{fb}}^{-1}$ for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of the $t\overline{t}$ cross section explicitly including $\tau$ leptons in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$. The measured value ${\sigma }_{t\overline{t}}=143\pm 14(\mathrm{stat})\pm 22(\mathrm{syst})\pm 3(\mathrm{lumi})\mathrm{pb}$ is consistent with the standard model predictions.

Figure 1

The $b$-tagged jet multiplicity for preselected events with one electron (top) or muon (bottom). Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total systematic uncertainty.

Figure 2

$E_{\mathrm{T}}^{\mathrm{miss}}$ distribution after the full event selection for the $e{\tau }_{\mathrm{h}}$ (top) and $\mu {\tau }_{\mathrm{h}}$ (bottom) final states. Distributions obtained from data (points) are compared with simulation. The last bin includes the overflow. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total systematic uncertainty.

Figure 3

The $\tau$ $p_{\mathrm{T}}$ distribution after the full event selection for the $e{\tau }_{\mathrm{h}}$ (top) and $\mu {\tau }_{\mathrm{h}}$ (bottom) final states. Distributions obtained from data (points) are compared with simulation. The simulated contributions are normalized to the SM predicted values. The hatched area shows the total systematic uncertainty.

Figure 4

Reconstructed top quark mass $m_{\mathrm{top}}$ distribution for the $\tau$ dilepton candidate events after the full event selection, in the $e{\tau }_{\mathrm{h}}$ (top) and $\mu {\tau }_{\mathrm{h}}$ (bottom) final states. Distributions obtained from data (points) are compared with simulation. The hatched area shows the total systematic uncertainty.