Hidden Particles in Weak Scale Physics and Beyond

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This award funds the activities of Professor Matthew Reece at Harvard University.The Standard Model of particle physics was developed nearly forty years ago and explains the vast majority of experimental data at distances as small as one one-thousandth the size of a proton. Nonetheless, it leaves behind many mysteries. Why is the gravitational force between two fundamental particles vastly weaker than the other forces? What is the dark matter that is far more prevalent in our universe than normal matter, but transparent to light and so far detected only through its gravitational effects? This research aims to provide theoretical support to the diverse experimental programs that are probing these and other questions. It will propose new strategies for analyzing data and extracting signals from the huge backgrounds present at the Large Hadron Collider experiments. This research will also build new models that will highlight discovery opportunities that current experimental searches may be missing. It will also study the implications of new experimental results for important paradigms like naturalness, which have shaped theoretical physics but still require a confrontation with experiment. The broader impact of this proposal will be include serving as a resource for local high school physics teachers and helping to communicate recent discoveries in physics to young students. By working with the existing, successful outreach program Physics Theorynet, which has built connections with Boston-area high schools, the PI will visit local high schools to answer student questions, explain the interplay between theory and experiment that goes into developments like the Higgs discoveries, and help students understand the career options available to them in science.The research supported by this award will proceed in several interconnected directions. It will assess the status of scenarios for natural supersymmetric theories, including the class of models called Stealth Supersymmetry developed by the PI. This will be done through simulation of the predictions of these models for existing LHC searches and through planning of how new, focused searches could better test these models. It will also assess the status of cosmology and dark matter in fine-tuned supersymmetric models, and develop a better understanding of how R-parity violation could evade overproduction of dark matter in scenarios with low-scale reheating temperatures. The research will help to ensure that the LHC experiments do not overlook possible long-lived particles, which could reveal the existence of new, higher scales to motivate future experiments. It will also study the connection between possible indirect detection signals of dark matter from space and hidden-sector physics that can be probed in high-precision terrestrial experiments. The PI will also study aspects of quantum field theory underlying all of these topics. By working on a broad research program, the PI will provide theoretical tools to maximize the impact of our very exciting, data-rich era.