The weak force is one of the four fundamental forces in our universe, along with gravity, electromagnetism and the strong force. Researchers have made the first experimental determination of the weak charge of the proton, a measure of the precise strength of the weak force’s influence on the proton.
Thomas Jefferson National Accelerator Facility is a U.S. Department of Energy Office of Science national laboratory. Jefferson Lab's unique and exciting mission is to expand our knowledge of the universe by studying the basic building blocks of matter within the nucleus: subatomic particles known as quarks and gluons.
In breast cancer screening, imaging based on nuclear medicine is currently being used as a successful secondary screening alongside mammography to reduce the number of false positives. Now, researchers are hoping to improve this imaging technique, known as molecular breast imaging or breast specific gamma imaging, by adding a new type of collimator - the variable angle slant hole collimator - to allow better image quality and precise location (depth information) within the breast.
The new superlattice photocathode, adapted by Jefferson Lab scientists for use in CEBAF, allows the use of readily available, fiber-based drive lasers, which require significantly less maintenance than laser types previously used in CEBAF. Introduction of these new lasers has reduced photo-injector downtime by more than 50% (from 2% total downtime to less than 1%).
Using tools that enable nuclear physics research into the heart of matter, scientists created a material for applications from aerospace to solar panels.
Understanding how the structure of hadrons emerges from QCD is one of the central challenges of contemporary nuclear physics. Recent advances in lattice field theory, developments in computer technology and investment in computer resources for fundamental QCD research have now made lattice QCD a powerful quantitative tool that provides an unprecedented opportunity to understand the phenomena arising from QCD from first principles, and to make precision calculations of the predictions of QCD.
Hall D of the 12 GeV upgraded CEBAF will house the GlueX experiment, which intends to map the spectrum of mesons, the hybrid mesons in particular, through photoproduction off protons. Knowledge of the spectrum of hybrid mesons will aid us in understanding the nature of the confinement of quarks within hadrons, since within hybrids the gluonic field binding the meson is excited. Just as the excited states of hydrogen taught us about QED, we hope the excited states of glue in mesons will teach us about the non-trivial aspects of QCD.
The ratio of the electric to magnetic proton form factors has traditionally been determined using the "Rosenbluth" or longitudinal-transverse (LT) separation method, in which the ratio is extracted from the angular dependence of the cross section at fixed momentum transfer, Q2. Recent measurements at JLab using the alternative, polarization transfer (PT) technique have found a dramatically different behavior of the ratio compared with the Rosenbluth results, leading to much discussion about the possible origin of the discrepancy.
