Trilinear Higgs boson coupling variations for di-Higgs production with full NLO QCD predictions in Powheg

The couplings of the Higgs boson to other particles are increasingly well measured by the ATLAS and CMS experiments. The Higgs boson trilinear self-coupling however is still largely unconstrained, mainly due to the low cross-section for Higgs boson pair production. We present inclusive and differential results for the NLO QCD corrections to Higgs boson pair production with the full top-quark mass dependence, where the Higgs trilinear coupling is varied to non-SM values. The fixed-order calculation is supplemented by parton showering within the Powheg-BOX-V2 event generator, and both Pythia8 and Herwig7 parton-shower algorithms are implemented in a preliminary study of shower effects.