Just when you thought you knew how everything fits together in the universe, WHAM! a team of four Notre Dame physicists and 47 colleagues has slammed a beam of high-energy particles into a tank of liquid hydrogen and found evidence for a rare new form of matter.
Last September the group of scientists from the United States and Russia announced the success of "Experiment E852," an eight-year effort at Long Island's Brookhaven National Laboratory aimed at finding a certain never-before-observed subatomic particle.
The experiment elated scientists because it yielded the first concrete proof that the long- suspected "exotic meson" really exists. It also provided a deeper understanding of the so-called "strong force," which holds together atoms. "If somebody eventually didn't find this, it would be quite a problem," ND physics professor Neal Cason, a spokesman for the E852 group, observed.
The Notre Dame team, made up of professors James Bishop, John Losecco, William Shephard and Cason, built and operated one of the experiment's particle detectors and was involved in all aspects of the project from planning to data analysis.
In examining debris from high-energy particle collisions, the physicists found a pattern indicating a previously unknown arrangement of quarks, the most basic building-block particle. Whereas protons and neutrons are made of three-quark combinations and ordinary mesons are a quark-antiquark amalgam, the physicists saw evidence for an exotic meson made of either two quarks and two anitquarks or a hybrid of quark, antiquark, and gluon, another elementary particle that carries the strong force.
The discovery of the exotic meson is a "very important benchmark" that will "set the mathematical scales for future experimentation and theoretical study," said Ted Barnes, an Oak Ridge National Laboratory physicist and professor of physics at the University of Tennessee.