The LHC is a proton–proton collider with centre of mass energy of 14 TeV, which started data-taking at CERN in 2009. Its purpose is to understand the nature of electroweak symmetry breaking and search for physics beyond the Standard Model. Two large general-purpose experiments are installed on the LHC, ATLAS [1] and CMS [22]. In these two experiments, much effort has been devoted to designing detectors sensitive to the broadest possible range of signatures of new physics, and to developing general and efficient search strategies.

While the Standard Model from a theory point of view is a complete renormalizable quantum field theory which does not require an ultraviolet completion, it is clearly experimentally incomplete: adding new stable particles at the weak scale with a typical weak coupling can, for example, explain the observed dark matter density in the Universe. Going up in energy, flavour physics in the quark sector is merely parameterized in the Standard Model, without any hint of what the underlying structure might be. Lepton flavour and in particular neutrino masses can be described by a see-saw mechanism that requires a heavy right-handed neutrino and an effective dimension-five operator at high energy scales. The measured almost-perfect gauge coupling unification in the Standard Model is in contradiction with proton decay searches, but it could easily be rescued by new physics at the weak scale.