Theoretical Physics, from colliders to gravity

Particle physics is the study of the fundamental building blocks of nature, how they interact and how they lead to what we observe from the smallest scales to the largest. The Standard Model (SM), which is built on quantum field theory (QFT), is an impressively accurate description of all data to date, from colliders to astronomical observations. Nevertheless, there are many aspects we do not understand from the pattern of particle masses to our lack of a quantum theory of gravity. The Large Hadron Collider (LHC) has been accumulating huge amounts of data, and famously has discovered a Higgs-like particle. Over the next decade the LHC will have a major impact, possibly discovering new physics beyond the SM. So far the only evidence for such new physics is neutrino mass & mixing, which may yet shed light on the pattern of particle masses, strength of the four forces, abundance of matter over anti-matter in the universe, dark matter and dark energy. Upcoming experiments will shed further light on these questions. We have close links to the LHC through the NExT institute and will help experimenters discover new physics, by devising strategies for searches and interpreting the data, for example through our easy-to-use interface (HEPMDB) to supercomputers. A common thread is the violation of the combination of charge conjugation symmetry (C) and parity (P), which may be observed soon in new sectors leading to major breakthroughs. In order to be sure that we have found new physics we need exclude subtle effects of the SM, or help deduce it indirectly by observing small deviations from SM. The strong nuclear force (QCD) can make this difficult, but we have outstanding expertise in computing these effects using state-of-the-art supercomputers, such as the IBM BlueGene/Q. It is important to continue to develop QFT, e.g. new tightly constrained theories have been found that become massless, at long or short distances. We use these to make better predictions of particle scattering and to better understand theories when mass is re-introduced or to work towards quantum gravity. The notion of holography has linked apparently very different systems such as QCD and Black Holes. We are developing it to learn more about a quantum gravity, and use gravity to study QCD including in extreme environments such as the cores of neutron stars.