Higgs boson pair production in SMEFT: shape and truncation studies

Abstract

We present a comparative study of the influence of Wilson coefficients on Higgs boson pair production cross sections in SMEFT up to dimension-6, also including loop-suppressed operators. Our study accounts for NLO QCD corrections, and is based on updated parametrizations of the cross section as a polynomial in the Wilson coefficients. We focus on differential distributions for the Higgs boson pair invariant mass, as well as the transverse momenta of the leading Higgs bosons, identifying benchmark scenarios exhibiting pronounced shape distortions in the $m_{hh}$ and $p_{T,h}$ distributions. While some of these scenarios remain physically meaningful under a purely linear truncation of the SMEFT expansion, others yield unphysical differential cross sections when quadratic dimension-6 contributions are omitted, exposing the breakdown of the linear approximation for large anomalous couplings.