Searching for Triple Higgs Boson Production with the ATLAS Experiment at the CERN LHC

About the Project

It's widely believed that the Standard Model (SM) of particle physics is an incomplete theory. The 125 GeV Higgs boson, discovered by the CERN ATLAS and CMS Experiments, is a crucial probe for physics Beyond the Standard Model (BSM) of particle physics. While searching for Higgs boson pair production helps probe the Higgs self-coupling (λ_HHH), the ultimate test of the Higgs potential's shape requires observation of triple Higgs boson production (HHH).

Triple Higgs production is extremely rare in the SM, making it an excellent channel to look for new physics. Many BSM theories, such as Composite Higgs Models or those involving extended Higgs sectors, predict significantly enhanced HHH production rates, potentially by orders of magnitude, compared to the SM. Observing or setting limits on HHH production is therefore a direct window into the nature of electroweak symmetry breaking and can reveal new, heavy particles or different fundamental interactions.

The student will develop cutting-edge analysis strategies to search for the extremely challenging production of three neutral 125 GeV Higgs bosons. This search will be performed using the full ATLAS Run-3 13.6 TeV proton-proton collision data. Searches will focus on a final state that offers excellent sensitivity to BSM enhancements, such as where two of the Higgs bosons decay to a pair of bottom quarks, and the third Higgs boson decays to two tau leptons, or another highly sensitive combination.

The student will gain expertise in machine learning techniques for signal-background discrimination and will also be involved in improving object reconstruction, such as developing advanced algorithms for tau lepton identification or jet substructure / particle-flow techniques to identify Higgs bosons decaying to b-bbar. Additionally, the student will have the opportunity to assist with hardware development for the ATLAS tracker upgrade (for the HL-LHC era), gaining invaluable experience in experimental detector physics.

Candidates who are interested in multiple projects within our group need only register their interest once and will be considered for all projects in which they have an interest. You will need to put down a named supervisor, please use Kristin Lohwasser and Trevor Vickey as contact persons.

For further Information, please email k.lohwasser@sheffield.ac.uk and T.Vickey@sheffield.ac.uk or look at the University’s website: https://www.sheffield.ac.uk/postgraduate/phd.

Further Information on the Particle Physics group in Sheffield and our projects can be found here: https://www.sheffield.ac.uk/mps/research/physics/particle

Funding Notes

This project is for Self-funded students or students with external funding.