Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question on whether positron/Down Quark can be fused.

  1. Mar 14, 2013 #1
    I was wondering that if positrons are antimatter and Down Quarks which are regular could be pushed together so that they break down into energy? The second question is whether this could be used for a form of fusion or fission reaction which ever is more accurate in this case by breaking a proton into 2 high energy free quarks and the energy of the first reaction?
  2. jcsd
  3. Mar 14, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF;
    I'd be surprised - positrons annihilate electrons. A down-quark would annihilate an anti-down quark.

    Technically a positron could get captured by an anti-proton to make an anti-neutron, releasing a photon.

    For a reaction to count as fission you have to end up with at least two nuclei, to count as fusion you have to start with at least two nuclei and end uo with at least one bigger one. Your examples don't count as either since they don't involve nuclei at all.
    In general, matter-antimatter reactions are neither fusion nor fission - they are their own kind of reaction called "annihilation".

    You do not get "free quarks" - at best you can have them in pairs as mesons, triples as nucleons, or as a quark-gluon plasma.
    Ejection of a meson from a nucleus is possible but iirc is never spontaneous - something else has to happen too.

    Does that answer your questions?
    Last edited: Mar 14, 2013
  4. Mar 14, 2013 #3
    yes that does thanks.
  5. Mar 15, 2013 #4


    User Avatar
    2017 Award

    Staff: Mentor

    The reaction positron + down-quark to electron-antineutrino + up-quark is possible via the weak interaction. This is not an annihilation process, but it could transform a neutron into a proton.
  6. Mar 16, 2013 #5
    So if that is what happens to a neutron then what about the proton wouldn't it then be broken apart and the mesons annihilate giving of energy that would ether break apart an atom of large size or escape into its surroundings.
  7. Mar 16, 2013 #6

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    If that (positron+down-quark) happens to a neutron in an atom, then the atomic number goes up one. The new nucleus follows the rules for that atom. if it turns out to be unstable then it decays normally. This sort of thing happens all the time.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook