Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



TECH SPACE
A Matter of Domination

File image for illustration purposes only. Credit: NASA/GSFC
San Francisco - Feb. 21, 2001
The seemingly unremarkable fact that the universe is full of matter turns out to be something physicists can't quite account for. According to the big bang theory, equal amounts of matter and antimatter were created at the birth of the universe, but precious little antimatter is to be found in the universe today.

Everything we see, from our bodies to our cars to the stars in distant galaxies, is made of matter. Cosmic rays and high-energy physics labs routinely create antimatter particles, but they soon interact with particles of matter and vanish in bursts of pure energy.

Somehow, within a fraction of a nanosecond after the big bang, matter gained the upper hand. Physicists believe subtle differences in the behavior of matter and antimatter led to a slight excess of matter in the very early universe. While most of the matter and antimatter created in the big bang quickly disappeared in a blaze of mutual annihilation, about one out of every billion particles of matter survived.

"Until the 1960s, the laws of nature were thought to be completely symmetric between matter and antimatter," says Michael Dine, a leading theorist and professor of physics at the University of California, Santa Cruz. "We now know that the symmetry is not quite exact, but our ideas about where the asymmetry comes from remain somewhat speculative."

Two new accelerators, one at the Stanford Linear Accelerator Center (SLAC) in Palo Alto and another in Japan, have begun to yield results that could reveal exactly how the symmetry between matter and antimatter is broken. The challenge for theorists like Dine will be to incorporate the new experimental results into a theoretical framework that satisfactorily accounts for the observed asymmetry.

In a talk to the February 16 annual meeting of the American Association for the Advancement of Science (AAAS) in San Francisco, entitled "Why the universe is Made of Matter," Dine presented various ideas put forth to explain the source of the asymmetry that enabled matter to dominate the universe.

The talk was part of a session on matter and antimatter on Friday. The latest results from accelerator experiments designed to measure the effects of the asymmetry were also presented at the session.

Evidence that the laws of nature are not completely symmetric with respect to matter and antimatter first emerged in 1964, when a violation of the so-called charge-parity (CP) symmetry was observed in ephemeral particles known as K mesons, or kaons. Researchers discovered a tiny discrepancy between kaons and anti-kaons in the way they decay.

In 1967, Soviet physicist Andrei Sakharov laid out the basic principles needed to understand this asymmetry and how it led to the dominance of matter in the universe. Sakharov showed that the violation of CP symmetry is just one of three conditions that must be satisfied to explain how an imbalance arose between matter and antimatter. There must also be violation of a conservation law, called the "conservation of baryon number," and the early universe cannot always have been in thermal equilibrium.

The prevailing theory of particle physics, called the Standard Model, readily accommodates the minute CP violation seen in the decay of kaons. But the violation of CP symmetry allowed by the Standard Model is too small to account for the amount of matter observed in the universe.

"Careful study in recent years has shown that you cannot produce nearly enough matter if the Standard Model is the whole story," Dine says. "To explain why we are here, there must be modifications of the laws of nature at very high energy."

One proposed modification of the Standard Model is supersymmetry, a set of ideas that suggest nature should exhibit a new symmetry at extremely high energies. Supersymmetry allows stronger CP violation than the Standard Model and also offers interesting ways to meet Sakharov's other two conditions for generating the asymmetry between matter and antimatter, Dine says.

While the Standard Model provides only one parameter that violates CP symmetry, supersymmetry predicts a whole new class of subatomic particles and new ways for CP violation to come about. If the theory is correct, the new particles predicted by supersymmetry should be detected when powerful new accelerators begin operating in the next few years.

Meanwhile, efforts continue to measure accurately the symmetry-breaking parameter predicted by the Standard Model. To do this, physicists are turning from kaons to their heavier cousins, the B mesons. At SLAC and at the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, new accelerators called "B factories" have been churning out vast numbers of B mesons and anti-B mesons in experiments designed to measure CP violation in their decays.

Some versions of supersymmetry and other proposed modifications of the Standard Model make quite dramatic predictions for the experiments now being conducted at the B factories. At the AAAS meeting, Dine provided a theorist's perspective on the latest results from those experiments.

Dine says he is hopeful that the new results will not fit neatly within the Standard Model. "The Standard Model has been a source of frustration because it can't fully explain where the asymmetry between matter and antimatter comes from. If these new experiments support the Standard Model, then we will still have a puzzle," he says.

Related Links
University of California-Santa Cruz
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express

TECH SPACE
Physicists Find Extra Dimensions Must Be Smaller Than 0.2 Millimeter
Seattle - Feb. 12, 2001
University of Washington scientists using gravity measurements to hunt for evidence of dimensions in addition to those already known have found that those dimensions would have to occupy a space smaller than 0.2 millimeter.


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only






Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.