Elementary Particle Physics
SLAC scientists study the collisions of particles accelerated to nearly the speed of light to search for answers about the fundamental structure of matter and the forces between subatomic particles.
These studies fall into two categories, each with a unique approach to making discoveries, which combine theory, experiment and computer simulation to move the science along.
At the energy frontier, scientists smash particles together at the highest possible energies to create and study exotic new particles and phenomena.
SLAC scientists contributed significantly to the world’s most powerful particle collider – the Large Hadron Collider (LHC) at CERN on the French/Swiss border. Since joining the collaboration in 2006, SLAC helped commission and operate detectors for the ATLAS experiment and is contributing to the ATLAS science program. SLAC is also involved in R&D for future upgrades to components of the ATLAS detector.
ATLAS and the LHC are intended to explore many of the deepest questions posed by our understanding of particles and forces: How do particles acquire their masses? Do the particles we have observed so far have much heavier, supersymmetric partners, and are these partners the missing dark matter? Do we see evidence for quantum gravity in the form of curled-up spatial dimensions or mini-black holes? The 3,000-strong ATLAS collaboration is poised to address these questions and make other discoveries at the energy frontier over the next decade and beyond.
SLAC is one of a few dozen ATLAS Tier 2 computing centers around the world, and one of only five in the United States, helping distribute and interpret the terabytes of data from the LHC's proton-proton collisions.
Many SLAC theorists are at work modeling the behavior of physics that might – or might not – leave traces in the aftermath of these collisions. Their job is to predict what clues might be hidden in the debris, and thus make it easier to spot traces of fascinating new physics.
SLAC is also involved in research and development for the next-generation electron-positron collider, whose potential for making important discoveries will be shaped by the results coming out of the LHC.
At the intensity frontier, scientists use powerful particle accelerators and ultra-sensitive detectors to seek out and measure nature’s rarest processes. This offers a second, complementary window into new phenomena at high energies.
SLAC led the construction and operation of the Enriched Xenon Observatory, located deep in a New Mexico salt deposit. The experiment is searching for a theorized type of particle decay which, if it exists, would happen only once in 100 billion times the age of the universe to any given xenon atom. Seeing this decay would prove that the neutrino is its own antiparticle.
SLAC’s BaBar detector finished its nine-year run and closed in 2008, but researchers are still analyzing the huge amount of data from the experiment – especially the billions of particles called B mesons produced by electron-positron collisions.
Among the questions the approximately 500 physicists and engineers in the BaBar collaboration seek to answer: If the Big Bang that gave rise to the universe produced equal amounts of matter and antimatter, what happened to the antimatter? The collaboration has delivered beyond expectations, providing not only a deeper understanding of the asymmetry between matter and antimatter, but also knowledge of new subatomic particles and decays.