Annual Report 2011

The Theory Unit (TH) continued to be a centre of excellence for the international theoretical physics community, welcoming visitors and organizing theory institutes and workshops. In 2011, it hosted 40 fellows, 50 students and over 800 visitors, with support from seven European grants related to research excellence. It also contributed to outreach and training efforts at CERN and elsewhere, organizing one school, three summer institutes and several workshops. Members of TH directly support the LHC physics programme in cooperation with the experimental groups through the framework of the LHC Physics Centre at CERN (LPCC). Set up in spring 2010, the LPCC continued to organize workshops and support the development of physics tools. Other initiatives include the Collider Cross-Talk discussion forum, which is led by fellows from TH and the LHC experimental groups at CERN, and a regular heavy-ion forum. Research activities in TH cover all areas of high-energy physics, as well as topics from particle astrophysics and cosmology. On average, one scientific paper was published per day in 2011. Particular effort went into refining the description of known phenomena in the context of QCD. A better understanding of such processes is crucial to the discovery of new physics at the LHC. The heavy-ion specialists focused on understanding how quarks and gluons lose energy in the hot and dense plasma created in heavy-ion collisions and on applying techniques from string theory to characterize the properties of the plasma. Looking at physics ‘beyond’ the Standard Model is essential. TH members investigated the origin of mass, the nature of the Higgs field and the quantization of the gravitational force. This effort implies taking into account data from a diverse range of non-collider experiments, in areas such as neutrino oscillations, B-physics, rare decays and dark-matter searches, as well as in astrophysics and cosmology. Research on more formal directions in theoretical physics included different aspects of string theory, applications of gauge/gravity correspondence, lattice QCD, supergravity and non-perturbative gauge dynamics.