Torrence, EricLuongo, Nicholas2024-01-092024-01-092024-01-09https://hdl.handle.net/1794/29149This dissertation presents the development of a boosted analysis in the searchfor the resonant production of a new heavy scalar X decaying to two Higgs bosons, which is predicted by some Beyond the Standard Model theories. The bbτ + τ − semi-hadronic decay channel of the Higgs bosons is considered. The analysis is developed using Monte Carlo simulated data and validated with 0.11 fb−1 of proton-proton collisions at √s = 13 TeV from the ATLAS detector at the Large Hadron Collider (LHC). Scalar X masses of 1, 1.6, and 2 TeV are considered and expected limits of 5.29 × 103 , 23.42, and 18.60 fb, respectively, are placed on the pp → X → HH cross section at 95% confidence level. These results are compared to existing resolved and boosted ATLAS bbτ + τ − analyses. A new method for di-τ identification and a kinematic neural network for event selection are also described. This dissertation contains previously published and unpublished material.en-USAll Rights Reserved.Electronic Thesis or Dissertation