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

How has antimatter responded to this bias?

[valros]

Wasn't this the previously supposed hypothesis? That the big bang held a slight matter bias. Its great that we can recreate it now. Also, how has antimatter responded to this bias?

Re:How has antimatter responded to this bias?

[JoshuaZ]

That is a hypothesis used by cosmologists but it isn't part of the Standard Model. The Standard Model predicts particle behavior, not as much the macroscopic stuff. For most purposes the Standard Model agrees with the cosmological observations. This is one example where the Standard Model may be missing something or need tweaking.

Re:How has antimatter responded to this bias?

[Anonymous Coward]

perhaps the "anti" in "antimatter" is dominate over the "identify matter" in "antimatter" and it sometimes acts as antiantimatter. so it isn't the universe giving a bias towards matter, it's antimatter being biased against itself.

Re:How has antimatter responded to this bias?

[DavidRawling]

The antimatter is very upset at the bias, and is petitioning for full recognition and the payment of reparations.

Re:How has antimatter responded to this bias?

[francium de neobie]

However, he died in a suicide bombing attack soon after he filed the petition, so the petition no longer matters.

Re:How has antimatter responded to this bias?

[silentcoder]

>Also, how has antimatter responded to this bias?

Antimatter has declared the bias to be a clear-cut case of discrimination and has applied for status as a protected minority.

Re:How has antimatter responded to this bias?

[nacturation]

Wasn't this the previously supposed hypothesis? That the big bang held a slight matter bias.

Slashdot has known this for more than a decade. After all, this isn't "news that anti-matters".

Re:How has antimatter responded to this bias?

[Trepidity]

To be fair, Slashdot has known both the affirmation and negation of nearly all propositions.

Re:How has antimatter responded to this bias?

[somersault]

That wasn't a suicide bombing, that was him trying to hug his girlfriend. While both their houses were alike in dignity, it turned out that their physical differences were too much for even love to overcome.

Re:How has antimatter responded to this bias?

[antifoidulus]

Including that one?

Re:How has antimatter responded to this bias?

[Colonel Korn]

This is one example where the Standard Model may be missing something or need tweaking.

Because good theories always make fundamental predictions that need to be contradicted by reality and then tweaked later in an ad-hoc fashion without ever revising their underlying principles. That's great science! Ah well, whatever gets you grants and funding right? In that case, status quo it is! We must always be openly hostile to all competing theories, refuse to publish them so they can be peer-reviewed, etc. That's progress.

In a generic sense it's a quite easy to publish a new, competing theory. That's the kind of thing most encouraged by the current peer review culture, as long as it's self consistent and matches observations.

Re:How has antimatter responded to this bias?

[jefu]

You are correct in that.

Re:How has antimatter responded to this bias?

[jefu]

That is not true at all.

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?

[crescente]

Their error, as stated in the linked abstract, is less than 0.3%. So, if you believe they're doing statistics correctly, yes, the signal is greater than the noise. More importantly, even, say 1.0 - 0.3 = 0.7% is HUGE: the common estimate of matter-antimatter asymmetry at the big bang was merely a billion-and-one to a billion. (linky: http://livefromcern.web.cern.ch/livefromcern/antimatter/academy/AM-travel02c.html). And that extra one in a billion is all the matter we have today.

Re:Is 1% significant?

[FrangoAssado]

Well, if they wrote a paper and submitted it to Phys Rev, you can rest assured they considered this (and it will be checked by many other physicists).

The abstract in the linked paper says the result they got differs by 3.2 standard deviations from the prediction given by the Standard Model. That's not conclusive, but it's significant. Surely they (or someone else) will keep looking in other data (from LHC, for example) to see if they can increase confidence.

Re:Is 1% significant?

[Trepidity]

Assuming that what the conclusion (p. 21) reports as "like-sign dimuon charge asymmetry of semileptonic b-hadron decays" is the number we're looking for, they do give a margin of error that's smaller than the asymmetry observed. They report the asymmetry as:

A = -0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst)

I believe the two errors are there because they breaking out the statistical margin of error (due to sampling) and systemic margin of error (due to accuracy of apparatus and setup).

Re:Is 1% significant?

[FTWinston]

Makes you wonder what would a universe that swung the OTHER way look like?

Exactly the same. Gravity wouldn't be affected at all by a reversal of electrical charge. EM would be the same, but the other way around (not that we'd notice, as all our points of reference would be the other way around), and the strong and weak forces would still work just like you'd expect.

Re:Is 1% significant?

[nedlohs]

I'm sure the scientists who wrote the paper never even considered that before submitting the article for peer review.

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.

Re:Sample Size?

[Daniel Dvorkin]

I'm trying to imagine what kind of sample size you'd need to represent, well, everything in the universe.

Sample size and significance calculations are generally done assuming an infinite population from which to sample, so "everything in the universe" is actually as close to perfect agreement between the math and the reality as you can get.

LHC can suck it!

[oldhack]

Your expensive tube is doing fat lot of good, eh?! You go Fermilab! LHC can suck it!

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

[cc1984_]

It would be so funny to discover now that the laws of physics ... be uneven in time. Maybe every 54.12 years the relation between produced matter/antimatter switches from 1:1.01 to 1.01:1.

You're not the first to think this (specifically the fundamental constants like the speed of light might be changing over time):

http://www.space.com/scienceastronomy/generalscience/constant_changing_010815.html

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

[Anonymous Coward]

So maybe Dragons really did exists once upon a time when the laws of physics were different.

Oh.. the creationists will love this.

Re:Uneven laws

[Joshua Fan]

The real problem facing physicists right now is the lack of a Fermilab in Australia to confirm such a possibility.

Re:Uneven laws

[Yvanhoe]

Because, of course, magically, no doppler shift will happen when you elevate c to 110%...

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

[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!

Re:new matter?

[chichilalescu]

no, this is doesn't fit the physics i know of.
in quantum field theory, you can describe the phenomena of a photon splitting into a particle-antiparticle pair that then anihilates to recreate the initial photon. these are the pairs that appear and disappear all the time (because of virtual photons that appear and disappear). However, a photon splitting into a particle-particle pair doesn't fit QFT.

Re:new matter?

[MichaelSmith]

Hawking radiation comes out of back holes. Because of quantum mechanics space is filled with virtual particles which come into existence and the annihilate themselves. Particles like an electron and an antielectron. Stuff like that. But if a black hole is nearby the electron could get swallowed, leaving the antielectron all alone in the world. The antielectron in this base becomes hawking radiation.

i am a psychologist

All right, okay. I should have read your post before I replied. How about this: particles come and go and nobody knows why. Sometimes they get lost which makes the other particles sad, so they wander off and get called "radiation".

Re:new matter?

[kix]

Right, of course you are correct. After having read http://en.wikipedia.org/wiki/Virtual_particle I actually understand that the question was rather silly. sorry about that. Although, if everyone read the correct wikipedia entries before asking things, there would be very few questions indeed ;)

thanks.

Re:Budget

[ShakaUVM]

>>The momentum of the Big Bang, the energy we will get back in the eventual collapse...

Eventual collapse?

Haven't kept up with physics, eh? =)

LHC can't contribute

[Bananenrepublik]

LHC is a proton-proton collider, Tevatron (where D0 is situated) an antiproton-proton collider. Therefore Tevatron provides a situation which is symmetric between matter and antimatter, LHC doesn't. The conclusion of the paper is that there is a 1% excess of matter in a situation that started with no preference for matter or antimatter. I don't see how LHC could contribute to this given that they are always starting with two matter particles.

Re:LHC can't contribute

[Shillo]

Had you read the abstract, you'd know that Fermilab's result is b+anti-b decay, not p+anti-p, so LHC is fine as long as they can specifically track which muons came from b quark decays.

As a matter of fact, they have a special detector just for that (it's not general-purpose, because b+anti-b pairs decay within centimetres from their creation point, so they actually drop particle tracker 5mm from the beam). See LHCb experiment.

Well

[Daath]

It doesn't matter. But it doesn't anti-matter, less.
Or something.

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

Bzzzt! Contestant #3426345 rings in with...

[IBitOBear]

What is, "there used to be a lot more matter and antimatter before they started canceling each other out and now we live amongst the debris"?

or, from my safety fifth-grader...

What is "the standard model is wrong"?

And I don't mean that in a bad way. The "flat earth" hypothesis was an _amazing_ deduction at its inception. It was only off by eight inches declination for every mile. This was a _tiny_ margin of error. But error compounds and so does any other form of tiny, so eight inches per mile, an error of ~.0126% (e.g. 8/63360) was enough to make the earth round.

Ta dah! 8-)

Re:Bzzzt! Contestant #3426345 rings in with...

[queazocotal]

It's been known for a long time that the standard model has problems.
To continue your analogy.

The earth is flat works really well as a model. If you're in a hilly terrain, you might suspect early on that the flat earth model isn't quite right.

To find out that earth is actually a slightly disorted sphere with a radius of some 6000km means that you have to go quite far (distance wise) to realise that the errors in the flat-earth model actually add up to a coherent alternative theory - a spherical earth.

It's much like this in physics.

Saying 'the standard model is wrong' - and giving plausible arguments - doesn't give much for alternative theorists to get their teeth into.

If however, you can produce a concrete measurement that can say 'The standard model is off by 0.3% here, 0.6% here, 1.2% here, and this looks _really_ like a curve of 0.5x+x^2 in the energy/bias ratio' - this can eliminate whole classes of alternate theories.

At the moment, string theory (and the descendant fields) suffer from an embarrasment of possibilities.
There are people arguing that the world is flat, round, toroidal, duck-shaped, ...

These theories are generally internally consistent, and can only be proved wrong with measurements of the real world. Without these measurements, the theories are interesting maths that you can make a career in maths about, but not predict the world in a useful way.

the weight of a human spirit

[mangu]

Yes, we do have an approximate idea of how much a human spirit weighs. The answer is 8e-23 g, or eighty trillionths of a trillionth of a gram.

This is calculated by estimating the average number of bits of information in a neuron and multiplying by the number of neurons in a brain. The energy needed for representing a bit of information is kT/6, where k is Boltzmann's constant (1.38e-23 J/K) and T is the absolute temperature of the medium which, in the case of a human brain, is nearly constant at 310 K.

Then energy is converted to mass according to the formula E=m*c**2, where E is the energy, m is the mass, and c is the speed of light in a vacuum.

In case you want hear from a physicist

[Anonymous Coward]

This is yet another reason why you shouldn't read mainstream media to get your physics news. Just reading the article summary makes me shiver all over.
Please, there are no fireballs at a particle collider and we are many many orders of magnitude in energy away from recreating the conditions after the Big Bang.
There is no miniature universe anywhere. Nothing went from being neutral to more matter than antimatter. Given that the (anti)matter in question here are (anti)muons
that would imply violation of charge conservation, which is not what they observed. This has nothing (well almost nothing, I'll explain in a sec) to do with why there is
so much more matter than antimatter in the universe, and the Standard Model does not suggest that there should be equal amounts either. The only correct
representation of facts in there is that the paper is indeed from the D0 collaboration and it has to do with seeing 1% more muons than antimuons.

Okay, so what did they do? They looked at decays of neutral B-mesons. These are curious mesons, because they oscillate back and forth between being a
B and an anti-B. If you ever took quantum mechanics: The propagating energy eigenstates are |B> +/ |anti-B> while |B> and |anti-B> are eigenstates of charge-conjugation+parity (CP).
The B can decay into a mu+ (antimuon) + other stuff, the anti-B can decay into a mu- (muon) + other stuff. (In both cases the other stuff has the opposite charge, so total
charge is conserved.) They saw a 1% asymmetry in the amount of mu+ vs. mu- which means that during the oscillation back and forth they end up 1% more often in one
than the other state which means there is a matter-anti-matter asymmetry in their behavior (technically there is CP violation in the mixing). The newsworthy fact is that in
the Standard Model this particular asymmetry (CP violation in mixing) is predicted to be about 25times smaller. With the uncertainties they quote that makes a 3-sigma discrepancy
which is regarded enough to claim "evidence of something" (you need 5 sigma to claim "observation of ..."), in this case direct evidence of new physics beyond the
Standard Model, which is what particle physicists have eagerly been looking for for the last decades. Personally, I'm holding my breath until I see the same measurement
from CDF (the other experiment at Fermilab). There have been many 3-sigma descrepancies in the past ...

As far as the universe is concerned, today we only have matter (forget about particle colliders, the point is there are no stars or huge clouds of anti-hydrogen out there).
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.
When the universe cooled down and all the anti-matter got annihialted the tiny excess of matter was left over, which is the matter we see today. To generate this asymmetry one
needs (among other things) CP violation. There is CP violation in the Standard Model, it's just not nearly enough (several orders of magnitude) to generate the required asymmetry in the early
universe. It is totally not straightforward what the 1% asymmetry in the B-anti-B mixing from above translates into in the early universe, although I'm quite sure people are looking at
it right as I speak. I would be very surprised if it was enough though.

Re:In case you want hear from a physicist

[Lord Ender]

I can picture you reaching for the nonexistant typewriter lever at the end of each line, then realizing it isn't there, then hitting the enter key to advance to the next line as a substitute.

Re:and worse, we could have had our own LHC

[wtbname]

I consulted my daughters "Jesus and You, and Science Too" text book, and it confirms that your post is bunk. Texas has never believed in science.

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.