Why does antimatter exist?

  1. I don't understand why antimatter exists in the first place. Could you explain why and how an asymmetry developed between matter and antimatter?
     
  2. jcsd
  3. Chronos

    Chronos 9,975
    Science Advisor
    Gold Member

    Dirac was the first to realize the relativistic version of the Schrodinger wave equation permitted anti particle counterparts to ordinary particles. We now know anti particles are routinely produced by high energy collisions between particles, and that anti matter should have existed in equal quantities shortly after the big bang. For reasons unknown, a slight excess [roughly one in a million] of matter particles survived the mutual annihilation frenzy that followed. The reason for this asymmetry is one of the great mysteries in science. Some as of yet unknown form of CPT violation is the prime suspect.
     
  4. You mean CP violation, right?
     
  5. Anti-matter exists only in the laboratory - artificially - through synthesis.

    Matter and Antimatter are absolutely identical and indistinguishable in every aspect
    other than charge.

    Helium is composed of 2 (+) protons, 2 neutrons and 2 (-) electrons

    Anti-Helium is composed of 2 (-) Anti-protons, 2 neutrons and 2 (+) positrons (anti-electrons)


    The reason matter exists in nature and Anti-matter has to be synthesized
    is due to Chirality (helical oriention) All matter follows the right-handed rule of chirality,
    Anti-matter follows the left-handed rule of chirality, and is not found in nature.

    Absolute symmetry is allowed in mathematics - in the Dirac equation for example,
    however this is not true of all interactions in nature.

    Equations are only abstract tools for calculating interactions in nature,
    Equations do not describe the causes of interactions, nor can they explain a natural phenomenon.

    Causes are the domain of practical experimental physics and not theoretical mathematics.
     
    Last edited: Jul 16, 2014
  6. For antiHe you need antineutrons. They are not the same as neutrons. Two neutrons meeting together will not annihilate, while a neutron with antineutron can annihilate .
    Also it would be much easier and more illustrative to speak of electron and positron, rather than going to a composite system.
     
  7. Correct, this was only a simplified explanation of the principle

    Anti-Neutrons are composed of Antiquarks and Neutrons are composed of Quarks
    this is the only difference - and is also due to Chirality.
     
    Last edited: Jul 16, 2014
  8. mfb

    Staff: Mentor

    Positrons and antiprotons exist in nature, they are just rare and if they hit matter (like earth) they annihilate quickly.

    And all other quantum numbers. And they are not absolutely identical, there is CP violation.

    This is just wrong. Only the weak interaction cares about chirality at all, and this interacts only with left-handed fermions ("matter"), not with right-handed.

    How is it "simplified" to list wrong particles?
     
  9. phinds

    phinds 8,752
    Gold Member

    Are you saying that there was no antimatter just after the big bang singularity or do you somehow exclude that from "found in nature" ?
     
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