Physics

The ATLAS Experiment at CERN

Steve Ahlen, Nafiun Awal, Clare Bernard, Kevin Black, John Butler, Robert Harrington, Michael Kruskal, Alex Long, Jeremy Love, Karishma Sekhon, James Shank, Zhen Yan, Saul Youssef

The ATLAS experiment is a large detector system being developed by a collaboration of physicists from all around the world to study very-high-energy proton-proton interactions at the Large Hadron Collider (LHC) at CERN, a laboratory for high energy physics near Geneva, Switzerland. It will be completed in 2007. This experiment will probe the origins of electroweak symmetry breaking and the particles associated with the new physics (such as the hypothetical Higgs Boson) that must appear at energies at the symmetry breaking scale. A figure illustrating the various parts of ATLAS is shown below. Boston University personnel are involved in the construction and installation of the muon detectors for ATLAS. The muon detector will occupy a region the size of a five-story building and will measure the trajectories of muons in a magnetic field with a precision of better than 1/10 of a millimeter. This permits the determination of the muon momentum, which will be an important ingredient in searches for new phenomena at the LHC’s energy scale, which will be an order of magnitude greater than currently available. The detectors are now built, and are currently being assembled into "sectors" that will be moved to the ATLAS experimental hall in early 2006. A photo of the first sector is shown below. Boston University is also playing a leading role in the development of computing and analysis tools that will be crucial when data begins to flow from the experiment in 2007. It is expected that many important discoveries in particle physics will be made at the LHC in the coming decade. These discoveries will improve our understanding of the fundamental particles and their interactions, and also of the nature of the early universe. One important goal of the LHC is to search for particles that may be responsible for the so-called "dark matter" of the universe. One possible type of particle that could account for this mysterious phenomenon are the particles associated with so-called _Supersymmetry Theories_.