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Why particles in a bubble chamber seam to disappear?

  1. Mar 8, 2009 #1
    are antimatter particles the explanation for why particles in a bubble chamber seam to disappear? ive read some on antimatter and supposedly some of it's been contained, how do they know what they have is antimatter?

    so many things theyre all confusing
     
  2. jcsd
  3. Mar 8, 2009 #2
    Re: antimatter

    If someone answers dangerbird's question can someone answer my question too?

    When antimatter and matter react and turn into energy, is 100% of the mass energy of both antimatter and matter converted into energy? I heard somewhere that something is produced, a neutrino? I have been told that the energy released is in the form of radiation, a gamma ray. If so, is the gamma ray(s) emitted in all directions from the point of annihilation? If there are multiple gamma rays, wouldn't they be emitted at the same time? What would dictate the direction of the gamma ray(s)?
     
  4. Mar 8, 2009 #3

    malawi_glenn

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    Re: antimatter

    The reason for why tracks in bubble chambers seem to disappear are many, if you provide an example of an reaction we can guide you.


    There is no such thing that *pure* energy, so there is always a conversion. When a particle and an antiparticle annihilate, it will create two photons if they annihilate via the electromagnetic force. The photons are sent back to back in the centre of mass system. The direction of the gamma rays in the lab-frame, in which we observe them, are decided by the relative initial motion of the particle and the antiparticle.

    If there are two leptons, one lepton and one anti-lepton, they can annihilate via the weak force aswell - creating two neutrinos via a virtual z_boson exchange.

    Similar, two quarks, one quark and one anti-quark can annihilate into gluons etc. since they also have the strong interaction.
     
  5. Mar 8, 2009 #4
    Re: antimatter

    Thank you very much for answering my question.
     
  6. Mar 8, 2009 #5

    Astronuc

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    Re: antimatter

    Charged particles in bubble chambers leave tracks by virtue of ioniziation of the atoms of the saturated vapor in the bubble chamber. The disappearance of a track means that a charged particle has interacted with another charged particle of an opposite charge, e.g. a π- interacts with a proton p and forms neutral particle(s), e.g. Λo and Ko. Neutral particles do not leave tracks, but eventually most decay to charged particles, which do leave tracks.
     
  7. Mar 11, 2009 #6
    Re: antimatter

    When antibaryons (e.g., anti proton) stop in a bubble chamber, it annihilates with a proton, and all of the energy is converted into pions, (plus, zero, and minus) the charged pions leave tracks ("star"), while the pi zero immediately usually decays into two 67 MeV photons. A stopping proton leaves only a dense track due to heavy ionization (Bragg peak).
     
  8. Mar 12, 2009 #7

    malawi_glenn

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    Re: antimatter

    hmm I have simulated pi0 decay produced in pp collisions, and that gamma-spectrum is very continuous.
     
  9. Mar 14, 2009 #8
    Re: antimatter

    It's strongly peaked in the pi0 rest frame, but they are 'never' at rest in a pp collision. I think you'll find it's the intrinsic pi0 boost which produces the spectrum.
     
  10. Mar 14, 2009 #9

    malawi_glenn

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    Re: antimatter

    Yes of course it is the pi0 boost ;-)
     
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