Research Areas
Proton Accelerator-Based Physics
Supporting Information
The most immediate goal on the particle physics roadmap as part of the energy frontier campaign is to fully understand the unification of the electromagnetic and weak nuclear interactions into a single, “electroweak” force. Scientists expect this to occur at an energy scale of about one trillion electron volts (TeV), or the terascale. The Standard Model has successfully explained almost all particle physics below 1 TeV in energy. Beyond that energy range, however, a new physical mechanism must be present to confirm Standard Model predictions. Originally scientists proposed that a single Higgs boson is the answer, but newer theories such as supersymmetry and extra hidden dimensions, suggest that multiple Higgs bosons could solve the TeV scale conundrum in the Standard Model. No matter which of these theories is proven to be correct, it will provide a deeper understanding of the fundamental nature of matter, energy, space and time. One thing is clear. The terascale will unlock a new world of physics for scientists to explore.
The Tevatron collides protons and antiprotons at an energy of 2 TeV. The LHC will collide protons at an energy of 14 TeV. Because of these high energy collisions and the fact that particles interact in different ways, scientists can use these facilities to study a wide variety of physics topics. All of the six known types of quarks can be produced in these interactions, but the heaviest—the top and bottom quarks—are of the greatest interest. Most of the force-carrying particles are also produced in these collisions. If the masses of predicted particles, such as the Higgs boson or suppersymmetric particles, are small enough, they will also be discovered.
The LHC program will substantially increase the ability of U.S. high energy physicists to explore physics beyond the Standard Model and will enable the U.S. to remain involved as a key player at the energy frontier. But while the LHC experiments will be just beginning to collect data, the well understood CDF and DZero detectors will continue to perform forefront searches for new physics at the terascale. This analysis includes making precision measurements of known particles, such as the mass of the W boson on top quark, that will indicate where the Higgs or other new physics is likely to occur. The number of top quarks accumulated and studied during the previous Tevatron collider run from 1992 to 1996 was less than 100. The new run, which started in 2001, has already produced an order of magnitude more top quarks and will provide far more precise measurements of its mass, spin and couplings.
The neutrino frontier also presents one of the most promising avenues to search for extensions of the Standard Model. In the last decade, a number of interesting new results have been reported by several different experiments, including the Super-K and KamLAND experiments in Japan and the Sudbury Neutrino Observatory (SNO) in Canada. These experiments provide compelling evidence that neutrinos do have mass and do change their identities as they travel. The Standard Model neither requires nor predicts these properties of neutrinos. Insufficient numbers of neutrinos and a wide range of energies, however, make it difficult to measure the mixing parameters. Dedicated proton beam facilities, such as one at Fermilab, present a unique opportunity to make high precision measurements of neutrinos. The NuMI/MINOS program is making decisive controlled measurements of fundamental neutrino properties, including neutrino mixing. These experiments will provide important clues and constraints to the theory of matter and energy beyond the Standard Model.
