Understanding electroweak symmetry breaking and searching for beyond Standard Model physics through measuring Higgs boson properties in the ATLAS experiment

by Magdalena Slawinska (IFJ PAN)

Thursday 28 Sept 2023, 11:00 → 13:00 UTC

The Higgs boson is the last discovered particle of the Standard Model (SM) and the only known fundamental scalar. It crowns the theoretical construction of the SM by providing masses to electroweak bosons through the mechanism of spontaneous electroweak symmetry breaking.
The essential feature of this  mechanism is the famous “Mexican hat” potential with non-zero vacuum expectation value. Measurements of Higgs boson coupling strengths to bosons and fermions,  in agreement with SM predictions within the uncertainties of the measurements, have experimentally confirmed the the Brout-Englert-Higgs mechanism of electroweak symmetry breaking. With more data being collected by the LHC, more subtle properties of  the Higgs boson can be revealed. These measurements will either confirm  the SM nature of this particle, leading to a better understanding of the SM, or hint at the existence of beyond Standard Model (BSM)  interactions.

I will present results of two sets of studies performed by the ATLAS experiment aimed  at measurements of the Higgs potential and searching for BSM deviations to its shape. One set constrains Higgs bosons self-interactions that result from the global shape of the Higgs potential. It is performed by  studying the production of the Higgs boson pairs. Due to a very small SM cross-section for the di-Higgs production,  an observation of this process with the currently available data would hint to the presence of BSM phenomena in the Higgs sector.

The other class of measurements  focuses on Higgs boson couplings to electroweak bosons, and thus probing the Higgs potential at its minimum.