What if the Higgs boson is not an elementary particle?

Project title: What if the Higgs boson is not an elementary particle?
Main applicant: Elin Bergeås Kuutmann, High Energy Physics
Grant amount: SEK 4 241 000 for the period 2026-2029

The aim of the project is to search for evidence of new phenomena using data from the ATLAS detector at the Large Hadron Collider, especially related to novel decay chains of hypothetical vector-like quarks (VLQs) and processes involving pairs of Higgs bosons and top quarks (ttHH). If a VLQ is found or if the production rate of ttHH is higher than predicted by the Standard Model of particle physics, the current best description of matter and forces, it could mean that the Higgs boson is not an elementary particle, but composite.

The team will consist of a PhD student and me. We will search for VLQs which decay via exotic scalar particles into final states with top and b quarks, which is the same final state as ttHH. Machine learning techniques will be used to separate the signal from the background. The similarities of the two processes will be utilised to run the two tracks in parallel.

The project will run for four years, starting in 2026.

A discovery of vector-like quarks or an observation of enhanced ttHH production, would lead to new insights into the nature of the Higgs boson and also revolutionise our understanding of fundamental particle physics. Maybe the Higgs boson is not an elementary particle after all.