High energy physics studies the elementary constituents of matter and the associated fundamental forces. The tools for these studies are experiments at particle accelerators operating at very high energies or at very high beam intensities, as well as ultra-sensitive large-mass detectors. These experimental setups give sensitivity to the laws of physics at very short distances. The Large Hadron Collider (LHC), launched in September 2008 at CERN, is the most spectacular realization of such a tool to date. On the other hand, the theoretical description involves mathematical theories, characterized by their intrinsic simplicity and predictive power, which reflect the symmetries of physical phenomena. More