Experimental Studies of the Higgs Mechanism in the Standard Model and Beyond

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Particle physics considers a vast range of scientific questions, from subatomic to cosmic scales. The State University of New York at Stony Brook Group supported through this award investigates such questions through experimentation at the highest available collision energies at the Large Hadron Collider (the LHC) at CERN, Geneva, Switzerland. These studies are relevant to the understanding of the Universe at its most fundamental level in the fleeting fraction of a second just after the Big Bang, and to why we see the Universe as we do now. The LHC is now operating at the highest collision energy ever achieved with man-made accelerators, 13 trillion electron volts or 13 TeV, and goals of the experimental program are to understand the nature of the Higgs Boson, discovered there in 2012, and to search for new physics beyond the Standard Model of Elementary Particle Physics. The research of the Stony Brook group is aimed to address these scientific goals from data collected with the ATLAS experiment, one of the major multipurpose detectors at the LHC. They seek answers to such questions as: is the newly discovered Higgs particle the one predicted by the Standard Model of particle physics or is it a part of a larger theoretical picture that includes new particles? Why is the observed mass of the Higgs boson so low, found to be 126 billion electron volts, or roughly 135 times the mass of the proton? What are the detailed properties of the force carriers of the electroweak interaction, the W and Z bosons, at high energy? These questions are critical to our understanding of the full context of the Standard Model of particle physics and to new physics that lies beyond the Standard Model.  Importantly, the Stony Brook group is providing managerial leadership for current upgrades of the ATLAS detector, to be ready by the end of the decade. These upgrades will allow the operation of ATLAS at ever higher beam collision rates to significantly increase the physics discovery capabilities of the experimental program. This effort provides for the participation and contribution of many university groups in the US, through support of technical personnel and education and training of young scientific researchers in the development and deployment of new, state-of-the-art instrumentation.