AAAS Session:Beyond E=mc²: Unveiling the Early Universe with High-Intensity Accelerators

Summary:

Subatomic processes in the early universe determined the matter content and the initial evolution of the universe. Yet many questions remain about those crucial first moments. The observations of dark matter, dark energy, and neutrino masses tell us that new physics exists beyond the standard model of particles and their interactions. But even the most powerful particle colliders cannot recreate the mass and energy scales that existed shortly after the Big Bang. Fortunately, particles and forces that exist at high energies subtly contribute to low-energy physics phenomena through quantum effects. Low-energy experiments repeatedly pointed to the existence of new particles and forces long before they were produced by particle colliders. Examples include the W and Z bosons, the charm quark, the top quark, and the not-yet-observed Higgs boson. This symposium will summarize the indirect searches for new physics with current and future high-intensity particle accelerators in the United States, Switzerland, and Japan. Using these innovative machines, physicists produce incredibly large samples of muons, B mesons, and neutrinos to look for effects predicted by theories beyond the standard model. They look for the transitions of, for example, muons into electrons, B mesons into their own antiparticles, and muon neutrinos into electron neutrinos. These low-energy processes are particularly sensitive to contributions from high-energy processes that have eluded detection so far.

Presentations:

Beyond E=mc²: Rare Particle Decays

Speaker: Craig Dukes, University of Virginia, Charlottesville, VA

Quantum effects in particle interactions can indicate physics phenomena at energies far higher than those of even the most powerful particle colliders. Low energy measurements, for example, pointed to the existence of the W and Z bosons, carriers of the electroweak force, many years before these particles were produced in proton-antiproton collisions at CERN. To find signs of new forces predicted by Supersymmetry and other theoretical models, rare particle decay experiments are looking for parts-per-trillion effects in the decays of long-lived subatomic particles such as muons and kaons, and parts-per-quintillion experiments are being planned.

Searches for New Subatomic Phenomena Using B Factories

Speaker: Gregory Dubois-Felsmann, SLAC National Accelerator Laboratory, Menlo Park, CA

Decays of B mesons, composite particles that contain a bottom quark, exhibit a matter-antimatter asymmetry that is spectacularly well described by the standard model. Yet this asymmetry is not sufficient to explain the dominance of matter in our universe. Theories that go beyond the standard model predict that new physics should lead to subtle effects in the decay of B mesons. Using high-intensity particle beams at the Stanford Linear Accelerator Center and the Japanese laboratory KEK, scientists have produced and analyzed billions of B meson decays, as well as comparable samples of charmed particles and tau leptons, enabling tests of the standard model with great precision and many searches for signs of the presence of new physics.

The Role of Neutrinos in the Evolution of the Universe

Speaker: Boris Kayser, Fermi National Accelerator Laboratory, Batavia, IL

Are neutrinos, one of the two most abundant types of particles in the universe, the reason we exist? The interaction of neutrinos with other particles may hold the key to explaining the evolution of the early universe. Leptogenesis, which involves additional, heavy neutrinos predicted by some theoretical models, could be the reason why our universe is made of matter while antimatter disappeared after the big bang. Using high-intensity, man-made neutrino sources, experimenters now have the means to understand the dramatic quantum behavior of neutrinos and can measure their rare interactions with other particles. Experiments in the United States, Europe and Asia could find evidence for the critical role that neutrinos played in determining the matter content of the universe.