CPF Seminar with Brendon Bullard

In the Standard Model (SM), the Higgs field spontaneously breaks electroweak symmetry and generates mass for fundamental particles. This mechanism is driven by the wine-bottle shape of the Higgs potential. The discovery of the Higgs boson at the LHC tells us that the Higgs field exists, but determining the shape of the Higgs potential remains a central goal of the LHC physics program. Observed differences in the shape of this potential from the SM expectation would have implications for early universe cosmology and the origin of the matter-antimatter asymmetry. The shape of the Higgs potential is best determined by measurements of the Higgs trilinear self-coupling accessed through searches for rare Higgs boson pair (HH) production. This seminar will present the search for HH production in the bbyy decay channel with 308 fb-1 of pp collisions at \qsrt{s}=13 and 13.6 TeV with the ATLAS experiment. This is the first LHC search for HH production with Run 3 data collected at record center of mass energy. It is also the first ATLAS physics analysis to use more than 300 fb-1 of pp collision data. The search leverages highly efficient photon triggers and the exquisite photon energy resolution to resolve the Higgs mass peak. Bottom quark jets are identified using a transformer-based flavor tagging algorithm to identify H->bb decays over the enormous continuum photon+multijet and significant resonant H(yy)+jets backgrounds. The analysis enhances the resolution of the H(bb) mass using a kinematic likelihood fit of the transverse momentum balance against the di-photon system.
 

I will present these new results interpreted as new physics in the trilinear Higgs self-coupling and in the context of the effective field theory formalism, which probes alternative scenarios for the role of the Higgs boson in electroweak symmetry breaking and anomalous interactions between the Higgs boson and top quark.