Using associated top quark production to probe for new physics within the framework of effective field theory

A data sample consisting of one or more top quarks produced in association with additional leptons is used to search for signs of new physics within the framework of effective field theory (EFT). This data sample corresponds to an integrated luminosity of $41.5~\mathrm{fb}^{-1}$ of proton-proton collisions produced in 2017 at a center-of-mass energy of $13~\mathrm{TeV}$ at the LHC and collected by the CMS experiment. The sample is selected by requiring events with multiple leptons and jets, including identified bottom quark jets; the events are then divided into categories based on the multiplicities of these objects. Sixteen dimension-six operators that can affect associated top quark production processes are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A fit is performed simultaneously of the 16 WCs to the data and limits on the values of the WCs are presented. The observed data are statistically consistent with standard model expectations, so the possibility of new physics is characterized in terms of 2 standard deviation confidence intervals for the WCs.