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Physics Beyond the Standard Model at the LHC and with Atom Interferometers

Final Report Summary - BSMOXFORD (Physics Beyond the Standard Model at the LHC and with Atom Interferometers.)

Elementary particle physics is entering a spectacular new era in which experiments at the Large Hadron Collider (LHC) at CERN will soon start probing some of the deepest questions in physics, such as: Why is gravity so weak? Do elementary particles have substructure? How do they get their mass?  Are there new dimensions? Can we produce black holes in the laboratory? The LHC is widely expected to shed light on such questions and lead to a new deeper theory of particle physics, which will replace the present standard model that was proposed forty years ago. The two leading candidates for new theories are the Supersymmetric Standard Model and theories with Large Extra Dimensions.
Since the LHC will be looking for the new model of particle physics, model building is flourishing.  Our vision for the ERC grant has been to create the highest caliber activity to explore the spectacular physics that is expected to emerge from the LHC. This is a once-in-a-generation opportunity that we do not want to miss. In order to find new physics at the LHC it is necessary to know what signals to search for ahead of time, or they will be missed. Therefore we have explored many scenaria for physics beyond the Standard Model that give novel signatures at the LHC. For example, “Little String Theories” predict a unique graviton mass spectrum with a mass gap followed by a quasi-continuum. Another example motivated by string theory is the presence of multiple particles called photini into which supersymmetric particles sequentially cascade. We also explored experimental signatures from theories of the fundamental particle masses, a fourth generation of fundamental particles, and theories with long-lived new particles.
One of the most spectacular and surprising connections in physics is between the laws on the shortest distance scales probed in colliders and the longest distance scales observed in astrophysics and cosmology. Many current experiments may shed light on this connection by searching for dark matter, the dominant form of matter in our universe, and observing the earliest moments of the universe. This is an exciting time as the coincidence of the LHC and the many current dark matter detection experiments may allow complementary probes of the nature of dark matter in the near future. Motivated by intriguing recent experimental results, we proposed several dark matter models, for example exothermic and luminous dark matter, that may be confirmed in upcoming experiments.
String theory suggests the presence of many ultralight particles called axions. We investigated novel astrophysical signatures of these particles, for example from gravitational waves emitted by black holes. Recent developments in cosmology and string theory suggest the presence of many universes. We have proposed ways to confirm the existence of such other universes via the signatures of the interface between our universe and others. Finally we explored the question of whether our universe truly had a beginning in the big bang.
One of the most exciting developments in physics in the last twenty years has been the unprecedented precision of atom interferometry (Nobel Prizes 1997, 2000, 2003). This lead us to propose laboratory tests of Einstein's theory of general relativity to levels that will rival or exceed those reached by astrophysical observations. So far this proposal lead to the construction of  a ten-meter atom interferometer at Stanford which will soon test Einstein's equivalence principle to fifteen decimals, and to seventeen decimals in the near future. This is 300 to 30000 times better than the best present limit using Lunar Laser ranging. We also proposed a gravitational wave detector utilizing this technology. This proposal has attracted interest from NASA and we are now moving forward with plans for a satellite-based gravitational wave detector in the next decade. Gravitational waves will open a new window into the universe, revealing the previously hidden physics of extreme astrophysical environments such as black holes and the early universe moments after the big bang.
We also proposed a new experiment using this atomic technology to search for dark matter in the form of axions. There are few experiments that can search for axion dark matter, and none in the region of parameter space that our proposal can cover.