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Friday February 09 12:51 PM EST
'Milestone' Study Challenges Basic Laws of Physics, Universe (universe of the very small)
By Robert Roy Britt       
Senior Science Writer, SPACE.com
An international team of researchers announced Thursday findings in the subatomic world that, if proven accurate, could upset a basic set of laws that scientists use to describe the physical world. The potential change in thinking would force cosmologists to reconsider the origin, evolution and daily operation of the universe.
The discovery involves the study tiny particles called muons. The data, generated at Brookhaven National Laboratory in New York, conflicts with previous measurements that explained the behavior of the subatomic particles. Scientists consider muons the most basic of particles. They are so tiny that they aren't made of smaller particles, yet they play an outsized role in shaping the physical world. Brad Keister, director of the nuclear physics program at the National Science Foundation, said the finding, if it holds up, will change how cosmologists view the evolution of the universe back to and including the Big Bang, though this basic theory of how everything began would not necessarily be tossed out.
The work, supported in part by the NSF, will also put researchers on the trail of new theories to explain missing matter in the universe, Keister said. Scientists have only accounted for some 10 percent or less of the mass known to exist. The rest, noted by how its gravity affects visible objects, is sometimes called dark matter. "It's a milestone," said Keister, who was not involved in the research. "If the result holds up, it's exciting simply because it says, 'There's more out there.'"
Tiny world with huge implications
A muon is a subatomic particle, something like an electron but heavier. The muon and many other small particles (with names like "quark" and "tau") have been discovered over the past several decades as researchers have developed ever more powerful particle accelerators used to study the goings-on of the subatomic world. The Standard Model of particle physics, which has been in development since the 1960s, explains the behavior of these particles. The model predicts, among other things, how a tiny muon should be affected as it moves through a magnetic field.
In particular, the Standard Model uses a thing called a g-2 value (pronounced "g minus 2") to measure the effect of three primary forces of nature on the muon.  The three forces are known as the weak force (which describes radioactive decay), the strong force (which binds the nuclei of particles together), and the electromagnetic force (which runs lights and allows radio communication). These forces alter a characteristic of muons known as "spin," which is somewhat similar to the spin of a toy top.  Gravity, the fourth known force in the universe, is not considered. This shortcoming in the Standard Model is something scientists would like to rectify with a larger, unified model of the physical world, says Morris Aizenman of the NSF's Mathematical and Physical Science Directorate.
"The Standard Model has worked extraordinarily well for over 30 years in describing three of the forces," Aizenman says. "It never attempted to combine the force of gravity with the other three."
Previous measurements of this g-2 value agreed with the Standard Model. But the new experiments, using a very intense source of muons and the world's largest superconducting magnet, has yielded what researchers expect are more precise results. And they don't agree with the Standard Model (which incorporates Einstein's theory of relativity).
"We are now 99-percent sure that the present Standard Model calculations cannot describe our data," said Brookhaven physicist Gerry Bunce, project manager for the experiment.
The finding could mean that new and strange types of physics might be possible. One idea that could benefit from the possible upheaval in thinking is called supersymmetry, a theory that predicts the existence of companion particles for all the known particles in the universe.
"Many people believe that the discovery of supersymmetry may be just around the corner," said Boston University physicist Lee Roberts, who also worked on the project. "We may have opened the first tiny window to that world."
These companion particles, while never before seen, would not surprise most theorists, who have long suspected that "empty" space is actually a sea of virtual particles that appear and disappear almost instantaneously. These particles, if found to exist, might account for some or all of the missing mass in the universe.
The behavior of the muons in the Brookhaven study seem to fit this idea, the researchers said. New studies with more powerful particle accelerators, two of which are planned over the next four years, would be needed to produce these companion particles, if they exist.
The scientists involved in the study -- 68 researchers from 11 institutions in the United States, Russia, Japan and Germany -- agree that more research is needed to confirm the work.
But further work by the group -- there is a year's worth of data still to analyze -- won't say what is out there, points out Keister of the NSF. It would confirm that, as cosmologists have suspected, there is more to the universe than currently meets the eye.
This interaction of the muon spin and the electric field is a specific consequence of Einstein's special theory of relativity. The experiment is performed with muons at this magic speed, namely 99.94 percent the speed of light. 4. To follow the precession of the muon spin, a measurement is required. Each muon is unstable (half have decayed after about 300 revolutions of the ring). When they decay, a positron (a positively charged electron, the anti-particle to the electron) is emitted whose energy carries, on average, information about the instantaneous direction of the muon spin at the time of the decay. A detector system measures the time and energy of these positrons and thus produces the experimental data of events versus time. The data look like any ordinary exponential (radioactive decay) with a modulation (wiggle) superimposed due to the muon g-factor. The scientists collected data from more than 1 billion muon decay events. The new measurement is a factor of 5.6 more precise than previous measurements made during the 1970s at CERN, the European laboratory for particle physics near Geneva, Switzerland, the researchers said.
The muon g-factor differs from the simple prediction of g-2 by a small amount, essentially one part in 800. This tiny difference is due to the muon's interactions with virtual fields. The Heisenberg uncertainty principle permits the muon to emit and reabsorb photons, electrons, positrons and even heavier particles such as the W and Z bosons, all of which can affect the g-factor. The electromagnetic, weak and strong interactions all contribute to the muon anomaly. Their combined effect is calculated in the Standard Model to a precision of 0.6 ppm. Participating institutions also include: Boston University; Budker Institute of Technology, Novosibirsk, Russia; Cornell University; Fairfield University; Heidelberg University, Germany; KEK Laboratory, Japan; RIKEN/BNL Research Center; Tokyo Institute of Technology, Japan; University of Illinois.     see next page   
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SCIENTIST FIND OLDEST KNOWN OBJECT IN UNIVERSE FEBRUARY 16, 2004 PASADENA, Calif. - In a discovery that offers a rare glimpse back to when the universe was just 750 million years old, a team of astrophysicists said Sunday they have detected a tiny galaxy that is the farthest known object from Earth. "We are confident it is the most distant known object," California Institute of Technology astronomer Richard Ellis said of the galaxy, which lies roughly 13 billion light-years from Earth. The team uncovered the faint galaxy using two of the most powerful telescopes — one in space, the other in Hawaii — aided by the natural magnification provided by a massive cluster of galaxies. The gravitational tug of the cluster, called Abell 2218, deflects the light of the distant galaxy and magnifies it many times over. The magnification process, first proposed by Albert Einstein and known as "gravitational lensing," produces double images of the galaxy. "Without the magnification of 25 afforded by the foreground cluster, this early object could simply not have been identified or studied in any detail with presently available telescopes," said astronomer Jean-Paul Kneib, of Caltech and the Observatoire Midi-Pyrenees in France. The discovery gives a rare glimpse of the time when the first stars and galaxies began to blink on, ending a period that cosmologists call the Dark Ages, said Robert Kirshner, an astronomer with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "The possibility is here we really are beginning to peek into that time," said Kirshner, who was not connected with the discovery. "People have gone there in their imagination — they've thought about it. Now we are getting the facts." The Hubble Space Telescope (news - web sites) revealed the first glimpse of the galaxy, backed up by observations made with the Keck Observatory's 10-meter telescopes atop Mauna Kea. The galaxy is just 2,000 light-years across. That's far smaller than the Milky Way, which is roughly 100,000 light-years in diameter. Cosmologists have predicted that early galaxies contained stars that were different from the ones that came into being much later in the history of the universe. But the astrophysicists' analysis suggests that the type of massive stars the galaxy contains were common after the end of the Dark Ages, Ellis said. "That's very interesting if it's true," Kirshner said. No one knows how long the Dark Ages lasted in the wake of the Big Bang 13.7 billion years ago.
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