UC Irvine

This article details two studies of Higgs boson properties using the vector-boson fusion production mode and the γγjj final state. Both efforts are based on a data sample corresponding to 164 fb−1 of s=13.6$$ \sqrt{s}=13.6 $$ TeV proton-proton collisions recorded by the ATLAS experiment at the Large Hadron Collider. The first study employs matrix-element-based optimal observables to constrain CP-odd couplings beyond the Standard Model within the Standard Model Effective Field Theory framework, expressed in the Warsaw basis. The second study exploits angular distributions to probe the Higgs boson’s couplings to longitudinally and transversely polarised W and Z bosons in the production of the Higgs boson. To maximise the sensitivity, the constraints of the CP-odd couplings are combined with those from a previous analysis performed in γγjj events in a data sample of proton-proton collisions at s=13$$ \sqrt{s}=13 $$ TeV, corresponding to an integrated luminosity of 140 fb−1. A significant improvement with respect to the previous analysis is achieved through the implementation of a new neural-network-based classification algorithm. All measurements are in agreement with the Standard Model prediction of a CP-even Higgs boson with the expected relative coupling strengths to longitudinally and transversely polarised vector bosons.