Probing EFT models with top-antitop quark production associated with boosted Z or Higgs boson.

A data sample containing top-antitop quark pair associated with a boosted Z or Higgs boson is used to search for signs of new physics within the framework of effective field theory (EFT). The samples correspond to an integrated luminosity of $137\,\text{fb}^{−1}$ of proton-proton collisions produced in 2016, 2017, and 2018 at a center-of-mass energy of 13 TeV at the LHC and collected by the CMS experiment. The sample is selected by requiring events with a single lepton, jets identified as bottom quarks, and a jet with high transverse momentum ($p_{\text{T}}$). A template is constructed from event kinematics centered around the boosted Z/H candidate, and a neural network trained to discriminate $\text{t}\bar{\text{t}}\text{Z}$ and $\text{t}\bar{\text{t}}\text{H}$ from $\text{t}\bar{\text{t}}$ events. To probe EFT effects directly, a parameterization of the signal rate in terms of the Wilson coefficients of the EFT operators is derived, and a fit is performed simultaneously of the 9 Wilson coefficients to the data. Limits on the values of the Wilson coefficients are presented.