# Measurement of the cross section for top quark pair production in association with a W or Z boson in proton-proton collisions at $\sqrt s$ = 13 TeV

## Abstract

A measurement is performed of the cross section of top quark pair production in association with a W or Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC. The data sample corresponds to an integrated luminosity of $35.9 fb^{−1}$, collected by the CMS experiment in 2016. The measurement is performed in the same-sign dilepton, three- and four-lepton final states. The production cross sections are measured to be $\sigma \left(\mathrm{t}\overline{\mathrm{t}}\mathrm{Z}\right)={0.99}_{-0.08}^{+0.09}{\left(\mathrm{stat}\right)}_{-0.10}^{+0.12}\left(\mathrm{syst}\right)\mathrm{p}\mathrm{b}$. The expected (observed) signal significance for the $t\bar t W$ production in same-sign dilepton channel is found to be 4.5 (5.3) standard deviations, while for the $t\bar t Z$ production in three- and four-lepton channels both the expected and the observed significances are found to be in excess of 5 standard deviations. The results are in agreement with the standard model predictions and are used to constrain the Wilson coefficients for eight dimension-six operators describing new interactions that would modify $t\bar t W$ and $t\bar t Z$ production.

## Abstract

A measurement is performed of the cross section of top quark pair production in association with a W or Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC. The data sample corresponds to an integrated luminosity of $35.9 fb^{−1}$, collected by the CMS experiment in 2016. The measurement is performed in the same-sign dilepton, three- and four-lepton final states. The production cross sections are measured to be $\sigma \left(\mathrm{t}\overline{\mathrm{t}}\mathrm{Z}\right)={0.99}_{-0.08}^{+0.09}{\left(\mathrm{stat}\right)}_{-0.10}^{+0.12}\left(\mathrm{syst}\right)\mathrm{p}\mathrm{b}$. The expected (observed) signal significance for the $t\bar t W$ production in same-sign dilepton channel is found to be 4.5 (5.3) standard deviations, while for the $t\bar t Z$ production in three- and four-lepton channels both the expected and the observed significances are found to be in excess of 5 standard deviations. The results are in agreement with the standard model predictions and are used to constrain the Wilson coefficients for eight dimension-six operators describing new interactions that would modify $t\bar t W$ and $t\bar t Z$ production.

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