The LBNL theory group carries out cutting-edge research in a wide range of areas in particle theory and cosmology, centered on models of new physics, precision measurements at high energy colliders, flavor physics, dark matter, and early universe cosmology. An essential aspect of the group’s operation is through the Berkeley Center for Theoretical Physics, a joint research center of the UC Berkeley Physics Department and the LBNL Physics Division, of which all lab and campus theorists are members. This further broadens the scope of the group’s interests to string theory.
To find out more about the various different research directions we are involved in, please continue reading.
New physics at colliders
The Large Hadron Collider (LHC) is currently probing physics at the highest energies produced in a laboratory. Both the increased energy and the considerably larger luminosity may allow the direct production of hypothetical particles beyond the standard model (BSM). One fundamental paradigm that has shaped theoretical particle physics over the past 40 years, namely whether the smallness of the electroweak symmetry breaking scale is due to new dynamics at energy scales around a TeV or not, is currently tested experimentally by the LHC. If there are no new particles or new dynamics up to the energy scale that can be probed by Run II at the LHC, it would imply that the fundamental parameters of the standard model determining the weak scale are tuned to at least the percent level.
The group seeks creative avenues to discover new physics, be it for models solving the hierarchy problem such as weak scale Supersymmetry (SUSY), for dark matter or exotic new physics scenarios. We highlight the signatures that can be expected for such models at the LHC and other experiments. Because of the breadth of our group, we are able to break down the boundaries between astro-particle physics, cosmology and collider physics. Since all of these areas will provide insight into fundamental physics, an inclusive view is crucial to fully interpret the plethora of experimental results in the coming years.
We are also continually looking for new physics in unexpected places: experimental searches are typically focused around a few models of new physics, such as the MSSM. The group interacts with the experiments to broaden the types of analyses that are carried out to ensure that new physics will not be missed.
Precision collider physics
As the luminosity of the LHC experiment is rising, and the experimental community is continuously understanding the detector environment better, the experimental uncertainties are continuously becoming smaller. The theory community is responding with higher precision theoretical calculations of known standard model processes, which are important for measuring SM parameters to an increased precision, and, more importantly, for predicting backgrounds for new physics searches.
The Berkeley theory group has a long tradition of providing precise theoretical predictions, and the expertise in effective field theory techniques and jet physics has provided a unique strength compared to many other theory groups. We are continuing to build on this strength. As the experimental collaborations continue to place more aggressive cuts to enhance signals over backgrounds, theoretical predictions in restricted regions of phase space are becoming ever more important. In these regions of phase space, higher order resummation is typically much more important than higher fixed order calculations, and the Berkeley theory group is working to provide the highest precision calculations, as well as guidance, to the community.
The next 10 years will be critical for tests of theories of WIMP dark matter. Direct detection experiments have already moved well below the scattering cross-section predicted for a WIMP interacting with a nucleus via the Z boson. Another crucial benchmark will be reached as direct detection experiments reach the cross section at which a neutralino DM candidate would be expected to scatter off the nucleus through the Higgs boson. At the same time, a lot of effort is dispensed to search for alternative dark matter candidates in very different mass ranges.
The Berkeley theory group contributes to this effort in several ways: We work on identifying new models of dark matter and study the predictions of those models in relation to existing and upcoming experiments. We also work closely experimental colleagues at Berkeley and elsewhere to identify now strategies to detect dark matter and perform the necessary calculations to predict the corresponding signals as accurately as possible. Finally, we search for signals of dark matter in the sky, by analyzing data recorded by various satellite-borne experiments.