This award funds the research of the PI Lisa Randall in a number of areas of particle physics and cosmology which are related to the phenomenological consequences of warped extra dimensions. Chief among these are LHC-related research along with model building and research related to Dark Matter. Many models Randall discusses are designed to address the hierarchy problem. The hierarchy problem remains one of the outstanding motivations for believing that interesting Beyond-the-Standard Model physics should exist at the weak scale. The question of why there is such a large separation between the Planck scale and the weak scale, or even how a theory incorporating quantum mechanics and special relativity can consistently maintain two such very different mass scales without a highly unlikely fine-tuning remains the major theoretical issue today for weak scale particle physics. Warped extra-dimensional geometry can potentially resolve the hierarchy problem. In this scenario, the cut-off varies over an extra dimension so that although the cut-off of a five dimensional theory is of order of the Planck scale, the local cut-off on a brane (which we will call the TeV brane) is of order a TeV. Randall is also guided by connections to general relativity solutions, string theory, and cosmology. Some work will be devoted to particular models, such as Randall-Sundrum (RS) warped geometry and its experimental signatures, supersymmetry and search strategy and model building, Higgs physics, and flavor physics. In addition Randall and colleagues will consider other models for comparison and consider potentially interesting signatures. With dark matter they will investigate new classes of models and consider possible implications for the various experiments of different types of models. In addition Randall plans to engage in more theoretical work related to general relativity and cosmological solutions.
The project also has many broader impacts. With the onset of the LHC there are many opportunities to explain particle physics and science in general to the interested public. The activities in which Randall is and will be involved include numerous public lectures and interdisciplinary conference talks, magazine and newspaper articles, including pieces Randall has written and articles Randall was interviewed for as well as appearances on TV, radio, and in documentaries.
Intellectual Merit The past few years held the promise of new phenomena and particles being discovered: at the Large Hadron Collider, in dark matter experiments, and in precision tests of flavor and the electroweak sector, and cosmological studies. We got hints that what we find—or don’t find—could be perplexing and require moving beyond the reservoir of ideas about the physics of the electroweak scale and beyond. Randall’s research has focused on LHC model building and phenomenology as well as on dark matter model building and search strategies. Given the hope of understanding the theory underlying the Standard Model she has done theory that was guided by LHC experiments and that helped analyze data as it came out. She has found new ways to integrate what we know and want to explain, and new ways to do LHC searches. Randall has also worked further on several broad new classes of models that accommodate the approximate coincidence of dark matter and baryon energy densities and go beyond the conventional WIMP paradigm. She has investigated new ways to do searches and interpret data in these new contexts as well as old ones. Broader Impact We also have seen that the new physics effects or new exotic phenomena might be at the edge of what is kinematically accessible, posing challenges to both theorists and experimenters to stretch ingenuity to the limits and uncover as much as we can. Randall has continued to pursue research whose aim is to find the fullest potential of LHC experiments and formulate consistent scenarios to more comprehensively test proposals. The broader impact of this research is its strong interaction with the experimental community. Already CMS has used Randall’s work to guide their first dedicated supersymmetry search. Randall’s work also overlapped with work done by astrophysicists and cosmologists. Better understanding of the underlying nature of space and matter has helped us improve our understanding of the universe’s evolution better as well. Randall served on BPA and participated in Astro2010 because of these critical connections. Randall has also continued her involvement in public communication of science. Her book Knocking on Heaven’s Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World, has come out in paperback and will be translated into numerous languages, providing a valuable opportunity to discuss current research, its reach and impact, as well as the nature and importance of science more generally. In addition, Higgs Discovery: The Power of Empty Space was released as a Kindle Single in the summer of 2012 as an update with recent particle physics developments.
