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Matter-Antimatter Bias Seen In Fermilab Collisions 304

Posted by kdawson
from the toe-of-god dept.
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.
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Matter-Antimatter Bias Seen In Fermilab Collisions

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  • by JoshuaZ (1134087) on Tuesday May 18, 2010 @02:32AM (#32249584) Homepage
    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.
  • by crescente (1334029) on Tuesday May 18, 2010 @02:47AM (#32249666)
    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: []). And that extra one in a billion is all the matter we have today.
  • by FrangoAssado (561740) on Tuesday May 18, 2010 @02:56AM (#32249704)

    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.

  • by Trepidity (597) <delirium-slashdot AT hackish DOT org> on Tuesday May 18, 2010 @02:57AM (#32249708)

    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).

  • by tylersoze (789256) on Tuesday May 18, 2010 @03:05AM (#32249748)

    Given the calculated ratio of photons to fermions during baryogensis the asymmetry is suppose to be even smaller than that, something like 1 extra particle of matter per 100 million if I remember correctly.

  • by Anonymous Coward on Tuesday May 18, 2010 @03:16AM (#32249784)

    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.

    It's extremely significant given some models show that a 1% bias would account for the Universe as we know it. Dead even, no Universe. A 1% bias and we get our Universe. 1% may not seem like much but it's massive when you are talking about the origin of the Universe. As far as experimental error 1% is a pretty massive error in particle physics. Add a few zeroes, 0.0001%, and it'd still be interesting but a full 1% is pretty massive on the scale we are talking about.

  • Re:Uneven laws (Score:5, Informative)

    by cc1984_ (1096355) on Tuesday May 18, 2010 @03:20AM (#32249808)

    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): []

  • LHC can't contribute (Score:3, Informative)

    by Bananenrepublik (49759) on Tuesday May 18, 2010 @03:38AM (#32249868)

    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:Budget (Score:3, Informative)

    by Trepidity (597) <delirium-slashdot AT hackish DOT org> on Tuesday May 18, 2010 @04:10AM (#32250002)

    As far as I can tell, the "big crunch" hypothesis isn't yet totally [] ruled out, though majority opinion is probably against it.

  • Re:new matter? (Score:4, Informative)

    by chichilalescu (1647065) on Tuesday May 18, 2010 @04:14AM (#32250022) Homepage Journal

    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? (Score:3, Informative)

    by kix (24024) on Tuesday May 18, 2010 @05:17AM (#32250246) Homepage

    Right, of course you are correct. After having read [] 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 ;)


  • by Shillo (64681) on Tuesday May 18, 2010 @05:26AM (#32250284)

    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.

  • by queazocotal (915608) on Tuesday May 18, 2010 @05:58AM (#32250452)

    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.

  • by mangu (126918) on Tuesday May 18, 2010 @06:15AM (#32250576)

    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.

  • Re:LHC can suck it! (Score:1, Informative)

    by Anonymous Coward on Tuesday May 18, 2010 @06:28AM (#32250644)

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  • by FTWinston (1332785) on Tuesday May 18, 2010 @07:20AM (#32250838) Homepage

    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.

  • by Anonymous Coward on Tuesday May 18, 2010 @07:55AM (#32251070)

    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.

  • []

    it was canceled in 1993, now its a data center

    it was going to be 40 TeV (the LHC is only 14 TeV). we would have already had been running it for years now, and the discussion topics here on slashdot could have been equivalent to discussions about columbus sighting land, in terms of amazing new discoveries by mankind

    and to make it incredibly freaky, this thing apparently was going to be in texas, way back when in 1993 when texas still believed in science

  • by Smallpond (221300) on Tuesday May 18, 2010 @08:28AM (#32251306) Homepage Journal

    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: []). And that extra one in a billion is all the matter we have today.

    That ratio means that the energy of the big bang was much less (100 / 1,000,000,000) than what it was previously estimated to result in the matter we see today. Kind of a large difference.

  • Re:Uneven laws (Score:2, Informative)

    by Anonymous Coward on Tuesday May 18, 2010 @09:04AM (#32251652)

    To be more precise, all those texts make it clear that these fire breathing dragons were ridden, sometimes by many people, and that they made thunderous noise and very bright light, while spewing smoke. []

    Which is more likely, fire breathing dragons, which man rode for vast distances, whereby for absolutely no reason and no explanation suddenly died out over night, without evidence, in historic times, or that as almost every civilization describes, depicts, and documents (including the Bible) in innumerable ways, we were previously visited from space? Even the Book of Enoch clearly describes rockets, space travel, and relativistic travel for Enoch.

  • by Colonel Korn (1258968) on Tuesday May 18, 2010 @09:14AM (#32251746)

    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.

  • by Lord Ender (156273) on Tuesday May 18, 2010 @10:29AM (#32252588) Homepage

    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:Uneven laws (Score:3, Informative)

    by IICV (652597) on Tuesday May 18, 2010 @01:53PM (#32255480)

    Uhm, everything we know about the universe is in fundamental conflict with the Biblical creation story. Seriously, there are maybe one or two things that could be considered factually accurate in the whole thing, and that's entirely by accident. The Earth existed before there there was light? There was light on Earth before there were stars in the sky? The Sun was created before the rest of the stars? The sky and the waters were the same thing and had to be separated? Are you going to say that none of these fundamentally contradict what we know?

    It makes no sense and is completely inconsistent with reality. It is a prehistoric myth, and is exactly as useful as the story of how the stars were created when Coyote scattered Cloud Woman's fire across the sky.

  • by Bigjeff5 (1143585) on Tuesday May 18, 2010 @03:35PM (#32256886)

    You're ignoring pressure. Objects under pressure hold together more tightly.

    The big bang is thought to have started from a state of extreme pressure - imagine the entire universe crushed into a space smaller than the size of an atom. That's the state of the universe pre-Big Bang, and it is sufficient to hold the universe in a state of matter.

    What is unclear is what triggers the release of all that massively pent up energy, which is what sent the universe into the high-energy state prior to the re-formation of matter and anti-matter, which happened when the Universe expanded far enough to start to cool back down. Matter was converted to energy, then cooled enough to re-create matter and anti-matter, which destroyed each other almost completely, all before the universe was even close to the size of the head of a pin.

    To get an extremely tame but somewhat similar example, look at what happens in a hyper-nova - The super-massive star's fusion slows down enough that it cannot maintain its shape, and crushes on itself, which creates a black-hole, which has far too much matter coming in than it can handle, so it explodes releasing massive amounts of energy in the form of extremely powerful gamma ray bursts. The Big Bang is a similar idea, just infinitely larger.

  • Re:Uneven laws (Score:3, Informative)

    by Black Gold Alchemist (1747136) on Wednesday May 19, 2010 @12:58AM (#32261162)
    Zero. Gravity does the rest.

Hacking's just another word for nothing left to kludge.