interesting stuff. here's where the math doh line up with the science....
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New clue to anti-matter mystery
A US-based physics experiment has found a clue as to why the world around us is composed of normal matter and not its shadowy opposite: anti-matter.
Anti-matter is rare today; it can be produced in "atom smashers", in nuclear reactions or by cosmic rays.
But physicists think the Big Bang should have produced equal amounts of matter and its opposite.
New results from the DZero exeriment at Fermilab in Illinois provide a clue to what happened to all the anti-matter.
Continue reading the main story Many of us felt goose bumps when we saw the result
Stefan Soldner-Rembold
DZero co-spokesperson
This is regarded by many researchers as one of the biggest mysteries in cosmology.
The data even offer hints of new physics beyond what can be explained by current theories.
For each basic particle of matter, there exists an anti-particle with the same mass but the opposite electric charge.
For example, the negatively charged electron has a positively charged anti-particle called the positron.
But when a particle and its anti-particle collide, they are "annihilated" in a flash of energy, yielding new particles and anti-particles.
Similar processes occurring at the beginning of the Universe should have left us with equal amounts of matter and anti-matter.
Yet, paradoxically, today we live in a Universe made up overwhelmingly of matter.
Unexplained result
Researchers working on the DZero experiment observed collisions of protons and anti-protons in Fermilab's Tevatron particle accelerator.
They found that these collisions produced pairs of matter particles slightly more often than they yielded anti-matter particles.
The results show a 1% difference in the production of pairs of muon (matter) particles and pairs of anti-muons (anti-matter particles) in these high-energy collisions.
"Many of us felt goose bumps when we saw the result," said Stefan Soldner-Rembold, one of the spokespeople for DZero.
"We knew we were seeing something beyond what we have seen before and beyond what current theories can explain."
The dominance of matter in the Universe is possible only if there are differences in the behaviour of particles and anti-particles.
Physicists had already seen such differences - known as called "CP violation". But these known differences are much too small to explain why the Universe appears to prefer matter over anti-matter.
Indeed, these previous observations were fully consistent with the current theory, known as the Standard Model. This is the framework drawn up in the 1970s to explain the interactions of sub-atomic particles.
Researchers say the new findings, submitted for publication in the journal Physical Review D, show much more significant "asymmetry" of matter and anti-matter - beyond what can be explained by the Standard Model.
If the results are confirmed by other experiments, such as the Collider Detector (CDF) at Fermilab, the effect seen by the DZero team could move researchers along in their efforts to understand the dominance of matter in today's Universe.
The data presage results expected from another experiment, called LHCb, which is based at the Large Hadron Collider near Geneva.
LHCb was specifically designed to shed light on this central question in particle physics.
Commenting on the latest findings, Dr Tara Shears, a particle physicist at the University of Liverpool who works on LHCb and CDF, said: "It's not yet at the stage of a discovery or an explanation, but it is a very tantalising hint of what might be."
Dr Shears, who is not a member of the DZero team, added: "It certainly means that LHCb will be eager to look for the same effect, to confirm whether it exists and if it does, to make a more precise measurement."
Paul.Rincon-INTERNET@bbc.co.uk
Fermilab Finds New Mechanism for Matter's Dominance over Antimatter
An analysis of Tevatron data shows an asymmetry in the way particles known as neutral B mesons decay
By John Matson The Large Hadron Collider may be up and running outside Geneva, but the particle accelerator it supplanted as top dog in the particle physics community appears to have a few surprises left to deliver. Data from the workhorse Tevatron collider at Fermilab in Illinois show what appears to be a preference for matter over antimatter in the way an unusual kind of particle decays, according to a new analysis in a Tevatron research collaboration.
Physicists and cosmologists seek such mechanisms to help explain why matter prevailed over antimatter in the early universe, when both should have been created in equal parts, yielding a storm of mutual annihilation and not the stable material structures—galaxies and the like—that fill the universe.
Some properties of high-energy physics have been shown to be fundamentally asymmetrical, producing matter more often than antimatter, but in quantities too small to explain the relative dearth of antimatter in the universe. The new mechanism observed at the Tevatron's DZero detector appears to work on a much larger scale, says Fermilab staff scientist Dmitri Denisov, co-spokesperson for the DZero collaboration, but whether it can explain the preponderance of matter today remains to be seen. In any event, the asymmetry does not fit with the long-reigning Standard Model of particle physics, suggesting that some hitherto unknown particle or interaction may be at play.
The DZero collaborators analyzed more than seven years of proton–antiproton collisions in the new study, which the group submitted to Physical Review D and published online May 16. As the exotic, short-lived particles produced in the collisions progressively decayed to more stable particles such as electrons, a collision product known as a neutral B meson appeared to decay more often into muons—unstable particles that exist for roughly two millionths of a second before decaying further—than into antimuons.
"While colliding protons and antiprotons, which creates neutral B mesons, we would expect that when they decay we will see equal amounts of matter and antimatter," Denisov says. "For whatever reason, there are more negative muons, which are matter, than positive muons, which are antimatter." According to DZero member Gustaaf Brooijmans, a physicist at Columbia University, "We observe an asymmetry that is close to 1 percent."
Brooijmans notes that other experiments have used B mesons to expose fundamental asymmetries in physics but that the results of those experiments have adhered more closely to the Standard Model's predictions. So-called B factories have been built to explore the properties of the unusual particles, but in a more limited scope than that available at the Tevatron. "There is one big difference" between the DZero result and those of the B factories, Brooijmans says. "We have access to the Bs meson, and B factories have access mostly to Bd."
Both Bs and Bd mesons (so named because they contain a strange quark or a down quark, respectively) are short-lived, decaying away in roughly 1.5 picoseconds, or 1.5 trillionths of a second. They are known as neutral mesons because they carry no net electric charge. In their brief lifetimes, they can oscillate between two forms, each the antiparticle of the other, Denisov explains. The difference is that Bs mesons oscillate much faster, giving them more flexibility to change from a matter progenitor to an antimatter progenitor, or vice versa. "Neutral B mesons are really interesting because they can basically go back and forth between matter and antimatter, to simplify things a bit, and we would have thought that they would spend an equal time as each," Denisov says. "What we're measuring now, it looks like they prefer matter."
Even within the halls of Fermilab, the new result from the tight-lipped DZero group came as a surprise, says theoretical physicist Bogdan Dobrescu, a staff scientist at the lab. "It's very exciting," Dobrescu says. "This kind of important announcement is not made too often." All the same, he says, the result must check out in other experiments before it can gain much traction. "It needs to be confirmed before we change the textbooks," he says.
Dobrescu says it is too early to speculate on how much of a player the new mechanism might be in establishing matter's prevalence in the universe. "However, all this notion of explaining matter–antimatter asymmetry should not be the central aspect of this discussion," he says. "We are up against something more important, which is, what are the laws of physics? The matter–antimatter asymmetry is just one implication of that."
It is fairly simple to put down on paper a new particle that could explain the asymmetry in B meson decay, Dobrescu says, but it is more difficult to reconcile those hypothetical particles with what is already known. "Most of the time, if you are careful, you will see that your choice is already ruled out by other experiments," he says.
If it turns out that a new particle is in fact responsible for the odd tendency of B mesons to favor matter over antimatter, it might be unmasked in the unprecedented high-energy collisions at the Large Hadron Collider, or LHC. But don't count out the workhorse stateside, which has a head start of many years—and reams of well-understood data—on its more powerful European counterpart. Brooijmans says his "gut feeling" is that such a particle should be observable at the LHC. "And who knows?" he adds. "It might be accessible at the Tevatron."
