Beyond the Standard Model Physics

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This award will provide support to a group of three PI's and an experienced senior faculty associate to work on the ATLAS experiment at the Large Hadron Collider (LHC) at CERN, a particle physics laboratory in Geneva, Switzerland. The LHC machine and ATLAS, a large particle detector facility, were built as basic science tools using funds from NSF and other agencies around the world. One of their primary objectives was to find the Higgs Boson, the last particle in the historically successful "Standard Model" (SM) that accounts for so much of the existence of, and forces between, known particles forming the matter in the universe. This effort has been successful. The next step in the experiments is to look for evidence for physics Beyond the Standard Model (BSM) that might, for instance, account for the presence of the mysterious "Dark Matter" that makes up so much of the mass of the universe. The LHC is about to begin run 2 at almost twice the energy ever explored in detail before. It is possible that particles from BSM could materialize at the higher energy. Two Higgs decay types, whose observation relies on techniques developed by this group, could provide the key to seeing BSM for the first time. The investigators will continue to train their algorithms to search for decays of heavy neutral Higgs Bosons into tau+tau- lepton pairs. New algorithms will also be developed to compute the tau pair invariant mass (with two missing neutrinos). They will also search for long lived states seen to emanate from displaced vertices. The long-lived particle search will explore the use of boosted decision trees (BDT) to improve event selection sensitivity and ways of combining events in which the decays occur in ATLAS subsystems. The group also has a number of well-defined service roles in the overall operation of ATLAS, including maintenance of the muon system software, database and data quality. They also work in the development of the new inner pixel detector, part of the phase 2 upgrade program. The group supports a vigorous broader impact program through public dissemination of the results from ATLAS. They also focus on training under represented students. One of the PI's (Goussiou) is also a Co-PI in the NSF QuarkNet outreach program.