SMEFT chromomagnetic dipole operator contributions to tt̄ production at approximate NNLO in QCD

We study higher-order QCD corrections for the production of a top–antitop quark pair ( tt̄ t t ¯ production) at the Large Hadron Collider in the Standard Model Effective Field Theory. We consider effects of new physics parametrized by the top-quark chromomagnetic dipole operator. We calculate new physics contributions to the total cross section at approximate NNLO, with second-order soft-gluon corrections added to the complete NLO result, including uncertainties from scale dependence and from parton distributions. We also calculate new physics contributions at approximate NNLO for differential distributions in top-quark transverse momentum.