Search for tri-Higgs Boson production in pp collisions at √s= 13 TeV with the ATLAS detector

After the Higgs Boson, with a mass of 125 GeV, was discovered in 2012, studies of single Higgs boson production have largely confirmed that this particle has similar properties to the Higgs boson predicted by the Standard Model (SM). Further studies on Higgs boson production rates represent the next crucial step to constraining the Higgs sector and allow the chance to refine measurements of the Higgs boson self-coupling. While previous searches have focused on di-Higgs, this analysis documents a new search, with 139 fb-1 of pp collisions at √s =13TeV collected by the ATLAS detector in LHC Run 2, for tri-Higgs (hhh) production in the bbbbbb final-state. This analysis focuses on a search for resonant hhh production model featured by a SM-extension to include two additional real-singlet scalars (TRSM), but will also set limits on non-resonant production. Small background rates benefit analysis sensitivity, however they also represent a major challenge and require precise background modelling. To estimate the 6b background, this analysis uses a reweighting of lower b-jet multiplicities. This analysis attempts to set limits for the first time on hhh production cross-sections. Analysis is currently blinded for both resonant and non-resonant searches and analysis techniques and expected significances will be presented.<br />