Measurement of the top quark pair-production in association with a W or Z boson in pp collisions at 13 TeV with full 2016 dataset at CMS experiment

The collected data in 2016 at the LHC at a center-of-mass energy of 13 TeV allows to study the heaviest set of standard model particles that could be observed so far. The precise measurement of the cross-sections of ttW and ttZ processes is of particular interest as they are effected of new physics, if present. Furthermore, the ttZ production is the most sensitive process for direct measurement of the top quarkâ??s coupling to the Z boson. The ttZ cross section was first measured by the CMS experiment in 7 TeV collisions, with a precision of about 50pct. More recent measurements of ttW and ttZ processes using the full data collected at 8 TeV collisions at CMS and multivariate techniques constrain the cross sections to the 25-30pct of their SM values. The measurement with 2016 data at a center-of-mass energy of 13 TeV achieved the 20pct precision level with the expected (observed) signal significance for the ttW production at 4.5 (5.3) standard deviations level, while for the ttZ 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 ttW and ttZ production.