CP-Violation and baryon asymmetry in the universe.

Discussion in 'Science' started by Goth, Sep 3, 2008.

  1. Goth

    Goth Grumpy Member

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    One of the great open problems in physics at the moment is the question of why the Universe has so much matter in it, and essentially no antimatter.

    If matter and antimatter (quarks and antiquarks, fundamentally) were created in equal amounts following the Big Bang, then all the matter and antimatter would annihilate, and the matter-filled Universe we see would not exist.

    A fundamental postulate of the laws of physics is CP-symmetry - that is, that the laws of physics are 'symmetrical' under CP-transformation (CP- as in a combination of both Charge and Parity operators.)

    In other words, basically, the laws of physics are "symmetrical" between matter and antimatter, since CP-symmetry is the symmetry between matter and antimatter. Particles and antiparticles should behave "symmetrically" in every way.

    However, as per the above, this isn't true. At least, it's not always true. There exists, therefore, some mechanism whereby CP-symmetry can be violated - CP-violation, an example of a symmetry violation in physics.

    The CP operator is the product of two: C for charge conjugation, which transforms a particle into its antiparticle, and P for parity, which creates the mirror image of a physical system. The strong interaction and electromagnetic interaction seem CP-invariant, but a slight degree of CP-violation is observed in weak interactions under certain conditions.

    The greater the degree of CP-violation present in the early Universe, the greater the amount of matter left in the Universe. Thus, the understanding of CP-violation plays an important role in cosmology, in explaining the amount of matter in the universe, which is a rather important quantity, from the point of view of physical cosmology.

    Quoteth Wikipedia a bit because I'm getting sick of writing and can't remember dates:
    From that last paragraph, of course, we arrive at Feynman's famous conjecture, which is absolutely true, that an antiparticle is a corresponding particle traveling backwards in time. That is indeed how Quantum Field Theory predicts the existence of antiparticles.

    The K0 (neutral K) meson (or Kaon) consists of a down quark and a strange antiquark - ds' - and its corresponding antiparticle K0' is of course made up of a strange and an anti-down, sd'.

    Similarly, the B0 is db', and the B0' is bd'. (B mesons, by definition, contain a b quark/antiquark, which is why they're named thus, and Kaons contain a strange combined with a non-strange quark.)

    These mesons can 'oscillate' back and forth - with a particle spontaneously turning into the antiparticle, and vice versa, like this:

    http://en.wikipedia.org/wiki/Image:Kaon-box-diagram.svg

    But the transition between particle and antiparticle and between antiparticle and particle don't occur at quite the same rate - because of the CP-violating term!

    Whilst CP-violation was first experimentally discovered, it was discovered in neutral Kaon interactions - but today, most experimental studies of CP-violation deal with the B-mesons.

    Two of today's best known particle physics experiments investigating CP-violation in the decay of B-mesons are the Belle and BaBar experiments - where B mesons are produced in electron-positron collisions using particle accelerators - the latter at the Stanford Linear Accelerator, and the former at an electron-positron synchrotron collider at KEK in Japan. The interaction points are surrounded by optimised detectors to watch the decay of the B-mesons created. When, say, a B0 decays into some stuff, say a K0 and a couple of leptons, the anti-reaction, a B0' decaying into the corresponding antiparticles, will occur, but at a different rate.

    The LHC-b detector experiment on the LHC is intended to be very similar in nature to these existing experiments - with similar goals.

    Well, I hope you found that interesting.
    Um, any questions?
     
  2. HeatVision

    HeatVision Member

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    That was a good read, thanks for taking the time to write it.
     
  3. wellonchompy

    wellonchompy Member

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    +5 insightful.

    BUT HOW!!?!?! Bring on the LHC to answer this, and inadvertantly discover even more ground-breaking science.
     
  4. Goose1981

    Goose1981 Member

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    Bought a copy of New Scientist this morning whilst i was out shopping for some nom nom's.

    Has a write up about the LHC in it. Haven't read it yet but i just can't get enough of this LHC thing. I don't understand much about it but the stats on the thing are amazing.. engineering pornography. :)
     
  5. Silenius

    Silenius Member

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    That was very interesting.

    My question: How do I stuff my brain back into my head? Nose, ears?

    oh btw goth, this is Cynic from atomic, I got the banhammer if you remember.
     
  6. luke o

    luke o Member

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    My basic understanding goes something like this:

    All things being "perfect" two equal quantities of matter and antimatter smashed together should completely anhilate each other.

    This basically says that this doesn't quite happen and some matter will be left over.

    Perhaps the quantities of matter and anitmatter involved in the big bang were mind bogglingly larger than we currently predict and what remains of normal matter is just that small percentage left over?

    I'd like to think that matter and time flowing forwards have a slight upper hand over antimatter and temporaly backwards flowing particles :)
     
  7. Assasinator_2

    Assasinator_2 (Banned or Deleted)

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    Goth, you know full well I'm a fan of your musings. Never give up doing them - they're more appreciated than you may think.
     
  8. neutralizer

    neutralizer Member

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    Speak for yourself, I just got a headache :D

    No in all seriousness, interesting stuff :thumbup: As above, I hope you keep up with your writings Goth, that way, everyday I get to learn about something new that just tells me that I know even less than I thought I did, lol.
     
  9. Whisper

    Whisper Member

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    This is one of the big questions left in physics, right?

    1. Where did all the Anti-Matter go?

    2. What is holding the Galaxies together, and if it mass, where is it?

    3. What gives particles mass?

    What others are there?
     
  10. Assasinator_2

    Assasinator_2 (Banned or Deleted)

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    4. How does relativity and quantum physics actually come together coherently?

    At the moment, they contradict. One has to be wrong to some extent. The fact that both work really well for a vast majority of aspects, though, means that it'll be minor changes to one or the other, in my mind. Either way, it'll be interesting to see what unifies them, though I'm not sure if I'll be alive to see it myself :(
     
  11. OP
    OP
    Goth

    Goth Grumpy Member

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    http://en.wikipedia.org/wiki/Unsolved_problems_in_physics

    Those three that you've mentioned are certainly three of the major, interesting ones at the present time - and incidentally, those three are of direct relevance to experimental particle physics and the LHC.

    It's quite well accepted today that there is indeed "dark matter", and it is comprised of weakly-interacting particles that have a significant amount of mass. Exactly what kinds of particles those particles are is an area of active interest at present.

    That's true - the proportion of extra matter that was left over relative to the amount annihilated could be as small as one part in 108, and that would be consistent with the observed density of the universe.
     
    Last edited: Sep 5, 2008
  12. gaz@jb

    gaz@jb (Banned or Deleted)

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    Bringing a bit more light to dark matter :thumbup:

    link
     
  13. Whisper

    Whisper Member

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    Yeah, my bad for missing that one.

    I do get the feeling, that on the area's I've touched upon, if one gets solved, the chances are likely that it may help solve the others as well.

    What happens if the LHC does the exact opposite of clarifying things and only serves to muddy the waters further?
     
  14. orchidophile

    orchidophile Member

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    Then we wait for the next smasher to see if that solves any of the riddles.

    Can't wait for the turn-on of the LHC and hopefully for some results regarding the higgs boson within a year or two.

    The New Scientist article was very good too, highly recommend anyone interested in it to give it a read. Great summary of the objectives and potential gains.

    Interesting idea about the matter-anti-matter quandary.
     
  15. led_blind

    led_blind Member

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    Very interesting stuff :) keep up the musings!

    I listened to Sir Roger Penrose & Dr Kip Thorne with Dr Karl this morning..link .. being no expert but exceedingly interested i want to ask this.

    Basically one of the proposed reasons for why we cannot find the antimatter is that it has been pushed to the boundaries of the universe. Now they said that for object that are very far away and that are moving away from each other , their apparent speed can break the speed of light rule and hence we may never be able to see it.

    Sorry if that does not make sense.... i need to re-listen. But if you do know what i am talking about how would this fit in with your musings?
     
    Last edited: Sep 5, 2008
  16. OP
    OP
    Goth

    Goth Grumpy Member

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    It's not that there is antimatter "hiding", it just isn't there. There's no reason why antimatter would be "pushed" without matter being pushed as well, and it would be annihilated.
     
  17. theFish

    theFish Member

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    Another excellent thread, Goth. Thanks for the read! :thumbup::thumbup:
     
  18. tornado33

    tornado33 Member

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    Here is a question. Does anti matter fall down under gravity, or up? Also, as gravity is "transmitted" by hypothetical particles canned gravitons, do anti gravitons signify antigravity?
    Thanks for the article too.
     
  19. Zylatis

    Zylatis Member

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    as yet there is not 'anti gravity' anti particles only differ in charge (and spin? i forget, i think spin is the same)
     
  20. tornado33

    tornado33 Member

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    Thanks for that.
     

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