Matter-Antimatter Bias Seen In Fermilab Collisions

ubermiester writes "The New York Times is reporting that scientists at Fermilab have found evidence of a very small (about 1%) average difference between the amount of matter/antimatter produced in a series of particle collisions. Quoting: '[T]he team, known as the DZero collaboration, found that the fireballs produced pairs of ... muons ... slightly more often than they produced pairs of anti-muons. So the miniature universe inside the accelerator went from being neutral to being about 1 percent more matter than antimatter.' This finding invites theorists to explain why there is so much more matter than antimatter in the universe, when the Standard Model suggests that there should be equal amounts of each." Here is the paper as submitted to Physical Review (PDF). The DZero team is looking forward to getting detailed data from the LHC once it ramps up operationally.

Comments

Is 1% significant?

[gman003]

For some experiments, 1% might be attributable to error. I've never done practical particle physics, though. Does this fall under experimental error, or is stuff like this usually re-creatable to seventeen decimal places?

I may not know much science, but I do know that margin of error is important.

Re:Is 1% significant?

[FTWinston]

Until an experiment demonstrates otherwise, or a convincing theory persuades me, I'll continue to suspect that an antimatter universe would appear identical to a "normal" matter universe, macroscopically at any rate. Provided that we didn't poke it too much. C-symmetery is likely close enough.

Re:Is 1% significant?

[c 0xFF]

Except in that universe, the + and - on circuit diagrams would actually make sense.

Budget

[MichaelSmith]

So presumably 99% of the mass-energy in the universe is currently energy, much of which must be potential and kinetic energy. The momentum of the Big Bang, the energy we will get back in the eventual collapse, light elements which will eventually fuse, and heavy elements which will eventually undergo fission.

Uneven laws

[Thanshin]

It would be so funny to discover now that the laws of physics are uneven in space...

That the same experiment gets you different results depending on which sid of the Milky Way you are...

Or they could be uneven in time. Maybe every 54.12 years the relation between produced matter/antimatter switches from 1:1.01 to 1.01:1.

Re:Uneven laws

[silentcoder]

That would not be a "discovery" but a confirmation. Many physicists have suggested such hypothesis in the past. Even more have suggested asymetry in time -t that at various ages of the universe the fundamental constants may have been different to what they are now.

There are a few pieces of evidence suggesting this (the rate of decay of Oklo's uranium COULD be explained that way - though a natural fission reactor is a more plausible one), and several physicists have conjectured that the fine-structure-constant may have changed over time, and that would be an explanation for the wrong speed of galaxies that wouldn't require cold-dark-matter.

Our estimates on the age of the universe have changed 4 times in the past 2 decades - generally, it got younger with the current consensus at about 13-Billion years.
Of course if any of the fundamental constants had changed over time or in different regions of space - in the end, it's simply a matter of how you travel through space-time, then that means all bets are off. The fundamental constants determine the laws of physics. Thus far, outside of singularities like the big bang or black holes (and Stephen Hawking thinks we don't even need THOSE to be singularities) there is no really strong evidence for it. It's possible, but unlikely - and if true, means it's mathematically impossible for us to understand the universe.

Re:Uneven laws

[Black Gold Alchemist]

If the laws are uneven in time, that could lead to perpetual motion among other interesting consequences.

For example, pretend that the speed of light is variable over time and remember that E=mc^2. On earth, we build a matter-antimatter annihilation laser and point it at a base in space. When the speed of light speeds up to c=1.1 the normal value, we fire off the laser, converting 10 g of matter into 1.08749377 petajoules. The light energy travels for a time, during which the speed of light slows back down to c. It hits a set up in the space base that converts the light back into matter. We divide by normal c, and are left with 12.1 grams of matter. We mail it back to earth, and send 10 g grams back to the laser (to repeat the process). The other 2.1 g is used as starship fuel, worth over 180 terajoules. Don't rinse, but repeat.

Re:Uneven laws

[Joce640k]

That would just mean that the "laws", aren't - in the same way that Newton's "laws" turned out to be not quite right when you're moving quickly.

And science would be cool about it. Excited about it, even.

Public imagination aside, scientists tend to celebrate when they're find out they were wrong (especially if it took big/expensive machines to do it...)

Re:Uneven laws

[silentcoder]

Hypothesis are a dime a dozen, theories are supposed to be hypotheses that have stood the test of time for a while, but the terminology often gets mixed up to the detriment of science (even by scientists).

That said, in this case - the people who made these hypothesis are highly respected phycisists who had genuine puzzles they were attempting to explain. In most cases so far - there ended up being other more plausible explanations, but I just don't imagine serious physicists proposing an alteration to a fundamental constant lightly.

Right now there is some puzzles in cosmology that suggest that the fine structure constant may have been slightly lower in the past, there is further very strong evidence that supports the possibility (notably - the energy of the background cosmic radiation is slightly lower, by almost exactly the amount it would be if this was true).
BUT - and this is a big but, in the meantime, two other explanations for the cosmic radiation difference have been proposed. In both cases they don't rely on a different fine structure constant shortly after the big bang. But their supporting evidence is still being tested. In the meantime - neither explains the puzzles that led to the proposal in the first place, so if either is shown to be accurate - cosmology still can't answer those.
That puts the weight of evidence currently on the side of a change over time in the FSC, if only because it explains more observations than any other available hypotheses.
Downside - if the FSC was different, that means a LOT of other differences, because the FSC is an amalgamation of several other fundamental constants including Planck's. Change that in the past, and it means the physics of the early universe was slightly different to ours, and such a difference is a mathematical singularity, it's impossible from our side of it, to predict what was on the other side.

Re:Uneven laws

[cfc-12]

I can heartily recommend Vernor Vinge's "A Fire Upon the Deep", which is set in a galaxy where the laws of physics do indeed vary widely depending on your distance from the centre of the galaxy.

Probably not what you'd call hard science fiction, but definitely one of the best "what if" books I've ever read.

Re:Uneven laws

[jenik]

I'd suggest you read Kuhn's Structure of Scientific Revolutions to see that science appears to work very differently than you (and many others) think. Scientist tend to prevent any substantial change in their paradigm as long as possible---for example by "tweaking" theories or devising auxiliary hypotheses.

Re:Uneven laws

[Myopic]

That is indeed interesting. My inference is that you just explained why C must be constant. You did a physical proof by reduction to the absurd.

new matter?

[kix]

I'm probably misunderstanding something here, but it seems that they have discovered that when the big bang happened, then because of this property, a bit more matter was created than anti-matter out of wherever they came in the first place, the rest of it annihilated with each other and everything else is made up from the "extra bits". This seems fairly reasonable.

Now, it is also known that new matter-antimatter element pairs are being created and annihilated all the time everywhere, this is where Hawking radiation comes from.

Does this new discovery mean, that it would be possible, that instead of an antimatter-matter pair a matter-matter pair is created sometimes instead and therefore the amount of matter in the universe is increasing (even if by a tiny amount)? Or are the conditions needed for this to happen too extreme to ever take place outside of big bangs and accelerators? Although as I understand some cosmic rays have far greater energies than accelerators.

Real physicists - please help me make sense of it all!

They fight for survival

[Laxator2]

The Tevatron is so thoroughly outclassed by the LHC that they have to take advantage of every opportunity to make a press release and show that they are still relevant. Once the LHC starts producing science data there will be impossible to justify funding for the Tevatron. The whole of Fermi Lab. (which uses about half the science money given by the D.O.E.) will be in danger of being closed, so they are fighting for survival. During the Bush administration they had to get private funding to avoid lay-offs. http://tierneylab.blogs.nytimes.com/2008/07/02/good-news-or-less-bad-news-for-american-science/

Re:They fight for survival

[Laxator2]

Honestly, I don't know much about what happened at CERN before LHC, I only remember that they had LEP, which was an electron-positron collider, while the Tevatron is proton-anti-proton. The "scooping" of experiments happens all the time, for example Cornell's collider was the main place to study B mesons for about 20 years, before SLAC built the BaBar machine that accumulated in one year as much data as the Cornell machine has accumulated in 20 years. Luckily, the people at Cornell were able to move to K mesons (which contain strange quarks rather than bottom quarks) in a different energy range and do precision measurements. This way they kept the funding going. As for the next collider, the US Congress has canceled SSC back in 1993 and there is little chance such a project (40TeV, as opposed to LHC's 14TeV) will ever get built in US. http://en.wikipedia.org/wiki/Superconducting_Super_Collider

Re:Authors

[mathfeel]

I know modern science is meant to be collaborative, but this paper has more than a page of authors! I note that they are listed alphabetically -- remind me to change my name to Aarons before taking up particle physics.

This is typical of "big science" that involves tons of people like experimental high energy versus "bench science" or "desk science" like everyone else.

Re:In case you want hear from a physicist

[Anonymous Coward]

That was a great explanation, many thanks! Only one part seemed a bit too sketchy:

As the theory goes after the Big Bang there were equal amounts of matter and antimatter, which would eventually have all annihilated into radiation and we wouldn't be here. The matter we see today is from a tiny, 1 in 10^9, asymmetry in the amount of matter vs. anti-matter that was generated dynamically by particle reactions after the Big Bang.

Something doesn't make sense in that description though, regardless of the asymmetry. Matter and antimatter coalesced out of a higher energy state in the Big Bang, so why would they appear only to immediately annihilate themselves against each other into energy again? Except for the tiny asymmetry, the before-and-after states of this process are identical because of energy conservation, so unless some other property changed as well, in effect it didn't happen.

In practice it wouldn't be a process of appear+annihilate at all, but a gradual cooling down of the high energy state through spacetime expansion until only the 1 in 10^9 asymmetric part remains. The sudden appearance and annihilation as two separate steps is completely artificial, and I don't see why that part of the Big Bang is being described that way, even in a theoretical model.

Actually, the Tevatron will be replaced

[students]

The Tevatron has to be partially removed to allow the construction of Project X, which is an accelerator that complements the LHC but does not compete with it. Fermilab is in no danger of being closed due to obsolescence. Many of the people who work there are working on the LHC, and there are many other experiments located at Fermilab.

After congress canceled the Superconducting Super Collider, Europe focused on exploring the "Energy Frontier" and American scientists have focused on the "Intensity Frontier." There are also lots of collaboration and experiments that do not fit into either category. Of course, the rate at which the "Intensity Frontier" is explored does depend on the federal budget, but it will get done eventually.

Re:In case you want hear from a physicist

[Bryan K. Feir]

There have been many 3-sigma descrepancies in the past ...

I have just three words on this:

"Alternating Neutral Currents".

(For those confused, Neutral Currents are interactions mediated by the Z boson. In the early 1970s, there was a race on to provide evidence for these, and there were press releases that had to be retracted because somebody jumped the gun and reported finding a Z before it was verified. This jokingly became called 'Alternating neutral currents', and several physicists had their credibility rather damaged in the process...)