LEAPS-MPS: Study of the Electroweak Mechanism through a Search for Beyond the Standard Model Higgs Bosons

The Standard Model (SM) of particle physics is a remarkably successful framework that explains the fundamental building blocks of matter and their interactions, leading to the formation of composite structures such as atoms. The 2012 discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) was a major milestone in confirming the SM. Yet, several fundamental questions remain unanswered: Why is the universe dominated by matter over antimatter? What explains the nonzero mass of neutrinos? What is the nature of dark matter, and how might it relate to the Higgs boson? Most importantly, is the Higgs particle discovered in 2012 the only one, or part of a larger family? These questions motivate theoretical extensions to the SM, including models with an expanded Higgs sector that predict the existence of additional Higgs bosons. The Principal Investigator (PI) proposes to search for these new particles using data from the ATLAS experiment in a decay channel that remains largely unexplored. This research is designed to enable undergraduate students to play a significant role in the computational analysis of LHC data and to engage in international collaboration through visits to CERN. A key broader impacts component of the project involves outreach to high schools in Maryland’s Eastern Shore, where students and teachers will be trained to analyze open ATLAS data and conduct hands-on experiments with particle detectors. Many extensions of the SM predict new scalar particles, similar to the Higgs boson, that arise from additional singlet or doublet fields and may mix with the known Higgs. The PI will investigate one such class of hypothetical scalars using ATLAS data, focusing on resonant decays into two bottom quarks and two W bosons in the 1-lepton and 2-lepton final states. This channel offers high statistical sensitivity but remains unexplored by ATLAS. The project involves several technical components, including the design of trigger strategies to improve signal selection efficiency, the use of kinematic fitting to enhance event reconstruction, and the development of multivariate classification frameworks informed by those fits. Additionally, the project will contribute to the calibration of b-jet triggers, supporting a wide range of ATLAS analyses. Analysis tasks such as Monte Carlo simulation, signal topology studies, and trigger efficiency evaluation will offer undergraduate researchers multiple opportunities to contribute meaningfully. This will be the first comprehensive ATLAS study of its kind, with the potential to set stronger exclusion limits or discover new particles. Undergraduate students will lead much of the work in close collaboration with the broader ATLAS Collaboration. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.