SMEFT everywhere: a NLO study of $\boldsymbol{pp \to t\bar{t}H}$ with decaying tops

TL;DR

This paper computes NLO QCD corrections to pp → t t̄ H in the di-lepton channel at the LHC, including dimension-6 SMEFT operators, and emphasizes the importance of consistent higher-order effects in top decays.

Contribution

It provides the first detailed NLO SMEFT analysis of pp → t t̄ H with decaying tops, including operator effects in production and decay, and compares stable and reconstructed top results.

Findings

Higher-order corrections and SMEFT operators significantly affect kinematic distributions.

Consistent inclusion of SMEFT effects in production and decay is crucial for accurate predictions.

Kinematic cuts and SMEFT operators impact observable shapes at the LHC.

Abstract

We present the computation of the next-to-leading order QCD corrections to the $pp\to t\bar{t} H+X$ process in the di-lepton channel at the LHC, including relevant dimension-6 operators $({\cal O}_{t\phi}, \, {\cal O}_{\phi G},\, {\cal O}_{tG}, \, {\cal O}_{tW})$ from the Standard Model Effective Field Theory. In our studies, higher-order corrections and effective operators are consistently included in the production part of the process as well as in the top-quark decays. We perform a detailed study of linear, cross, and quadratic contributions and their uncertainties, including renormalisation group effects. Our findings are presented at the integrated and differential cross-section level for the LHC Run III center-of-mass energy of $\sqrt{s}=13.6$ TeV. Finally, we provide predictions for $pp\to t\bar{t} H+X$ with stable top quarks and compare them with the results in which top quarks are reconstructed from their decay products. We show that kinematic cuts, as well as higher-order effects and SMEFT operators in top-quark decays, are important and should be consistently considered together, because they have a significant impact on the shape of the standard observables measured for the $pp\to t\bar{t}H+X$ process at the LHC.