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

An important test of the electroweak symmetry breaking would be to establish evidence of the Higgs boson self-coupling (_hhh), which is directly linked to the shape of the Higgs potential. This can be accomplished through a measurement of Higgs boson pair production. It's also possible that the 125 GeV Higgs boson discovered by the CERN ATLAS and CMS experiments is only one of several neutrally-charged Higgs bosons predicted by theories beyond the Standard Model of Particle Physics. Many of these theories predict the existence of a more massive Higgs boson that is able to decay into two lighter 125 GeV Higgses, which could appear as a resonance in the di-Higgs invariant mass spectrum. Some physics beyond the Standard Model could also enchance the di-Higgs production cross-section in a non-resonant manner. The student will develop analysis strategies to search for the production of two neutral 125 GeV Higgs bosons, and then carry out a measurement of _hhh using the ATLAS Run-3 13.6 TeV proton-proton collision data. Searches will focus on a final state where one of the Higgs bosons decays into two tau leptons, and the second Higgs boson decays to a pair of bottom quarks. As a key element of this search, the student will participate in developing algorithms for tau lepton identification. The student will also have the opportunity to play a leading role in the statistical combination of ATLAS di-Higgs search channels. There is also a possibility for hands-on detector work, by assisting with silicon module construction for the ATLAS tracker upgrade which is planned for installation following Run-3 of the LHC