More than a dozen faculty and students from the University of Colorado at Boulder are part of an international team that has launched an unprecedented experiment in an attempt to explain how the universe聮s matter came to exist.
Taking place inside a giant underground machine at Stanford University, the research involves shooting beams of sub-atomic particles at each other, which creates particles not normally seen in nature. The smallest particles, known as B mesons and anti-B mesons, may hold the key to the existence of all the matter in the universe, which makes up everything from stars and planets to people and plants.
The massive facility, known as the Asymmetric B Factory at Stanford聮s Linear Accelerator Center, was designed and built by about 650 scientists and engineers from 10 nations at a cost of nearly $300 million. It began operating in late May.
"I聮m incredibly optimistic about this project," said Associate Professor Patricia Rankin of CU-Boulder聮s physics department, a co-investigator on the project. Rankin, along with CU physics Professors Bill Ford and Uriel Nauenberg and Associate Professor Jim Smith, four postdoctoral researchers and several graduate students and technicians are involved in the project, which brings in about $1 million a year in federal grants to the CU-Boulder campus.
Cosmologists believe that within a trillionth of a second after the Big Bang in a flash of incredible heat, the universe created equal quantities of matter and antimatter. While atoms of ordinary matter contain a nucleus surrounded by negatively charged electrons and positively charged protons, atoms of antimatter contain positive electrons and negative protons.
At the instant following the Big Bang, cosmologists hypothesize nearly all of the matter and antimatter particles destroyed each other. But about one in every billion matter particles escaped destruction, enough to build today聮s universe.
The idea behind the Stanford experiments is to understand why the universe contains so much more matter than antimatter, said Rankin. "The fundamental question is where has all the anti-matter gone?" said Rankin. "As an example, if half of the material in the universe was antimatter and half was matter, if two people shook hands it could cause both of them to explode."
The B Factory at Stanford creates thousands of high-speed collisions between clumps of high-energy electrons and identical but oppositely charged particles known as positrons. The explosive collisions already appear to be producing B mesons, which decay swiftly -- in about a trillionth of a second.
The CU-Boulder team has been working on a sophisticated detector known as a "drift chamber" consisting of 27,000 wires strung through a gas medium. There are five additional detectors in the B Factory to measure products of B meson decays.
"These B mesons decay so swiftly that we have to reconstruct the decay of the particles indirectly using the devices contained in the detector," she said. "Because the occasional matter particle survives while antimatter particles do not, at some level we are probing why nature is not quite perfect."
Scientists believe a small imbalance between matter and anti-matter arose in the early stages of the universe聮s evolution, resulting in a slight excess of matter, said Rankin. The energy created when the matter and anti-matter destroyed each other resulted in what is now known as "cosmic microwave background radiation."
This radiation, which is found throughout the universe, is the remnant heat from the Big Bang and is now less than 3 degrees above absolute zero.
Some of the data generated by detectors at the Stanford facility over the next decade will be analyzed by undergraduate and graduate students at CU-Boulder, said Rankin.
A similar machine to measure matter and anti-matter has just been completed in Japan, creating a "neck-and-neck race" to solve the problem, she said.