The large hadron collider project

Abstract

Knowledge of the fundamental constituents of matter has greatly advanced, over the last decades. The Standard Theory of fundamental interactions presents us with a theoretically sound picture, which describes with great accuracy known physical phenomena on most diverse energy and distance scales. These range from 10 −16 cm, inside the nucleons, up to large-scale astrophysical bodies, including the early Universe at some nanosecond after the Big-Bang and temperatures of the order of 10 2 GeV. The picture is not yet completed, however, as we lack the observation of the Higgs boson, predicted in the 100–500 GeV range — a particle associated with the generation of particle masses and with the quantum fluctuations in the primordial Universe. In addition, the Standard Theory is expected to undergo a change of regime in the 10 3 GeV region, with the appearance of new families of particles, most likely associated with the onset of a new symmetry (supersymmetry). In 1994, the CERN Council approved the construction of the large hadron collider (LHC), a proton–proton collider of a new design to be installed in the existing LEP tunnel, with an energy of 7 TeV per beam and extremely large luminosity, of ∼10 34 cm −2 s −1. Construction was started in 1996, with the additional support of the US, Japan, Russia, Canada and other European countries, making the LHC a really global project, the first one in particle physics. After a short review of the physics scenario, I report on the present status of the LHC construction. Special attention is given to technological problems such as the realization of the super-conducting dipoles, following an extensive R&D program with European industries. The construction of the large LHC detectors has required a vast R&D program by a large international community, to overcome the problems posed by the complexity of the collisions and by the large luminosity of the machine.