The effective field theory as a searching tool for presence of new physics in tt production with CMS

Despite its success, the standard model (SM) presents some important shortcomings, and because of these there has been a long search for physics beyond the SM which can be associated to the production of new particles. Since for the moment there is no clear evidence of this we are motivated to use effective field theory to characterise corrections of the Lagrangian of the SM. The CMS experiment uses the effective field theory (EFT) with four different approaches, based on: 1) the reinterpretation of inclusive measurement, constraining the Wilson coefficients by using EFT parametrizations; 2) relying on reinterpretation of differential measurements at particle and parton level; 3) hybrid EFT measurements at detector level; 4) by characterising EFT directly with the data. Measurements of top quark tt differential cross-sections using simulated events produced in proton-proton collisions are presented. The differential cross-section is defined as a function of kinematic variables for the three decay channels: all-hadronic, semi-leptonic and dileptonic at particle and detector level. The cross-section has been measured for the SM events and EFT using the ctG, cQq81 and ctq8 Wilson coefficients, which were the most relevant. We analyse the different effects that are presented in each channel and also which are the relevant kinematic variables in each case. Based on the differential cross-section histograms we calculate the ratio between EFT and SM production, and analyse the trend of the linear fit in order to see which variables could help us constrain more the Wilson coefficients.