An event generator for $h\to b\bar{b}$ decays at NLO in SMEFT matched to a parton shower

Abstract

We present a Sherpa implementation of NLO corrections in dimension-six Standard Model Effective Field Theory (SMEFT) to the benchmark process $h\to b\bar b$. The calculation includes NLO QCD corrections matched to a parton shower using an MCatNLO-type framework for decays. Virtual weak effects are included as two-body matrix-element corrections in different electroweak input schemes, with the corresponding decay events also evolved with the QCD parton shower. We present numerical results for the inclusive decay rate and for differential distributions in the Higgs-boson rest frame, and illustrate how the decay implementation can be combined with an independently generated production sample by embedding it in associated $Zh$ production at the LHC. This proof-of-principle implementation demonstrates how NLO SMEFT corrections can be incorporated into the widely used Sherpa event generator, providing a basis for extensions to other processes and for SMEFT studies with realistic final states and fiducial cuts within that framework.