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Reason for particle decay

  1. Jan 30, 2013 #1
    why is that particles such as the tau muon have a short lifespan and why is it that particles decay into other partcles? furthermore, what are the process that occur in particle decay?
  2. jcsd
  3. Jan 30, 2013 #2


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    Physics cannot explain "why" - it can just describe the observations. Tau particles have a possible decay, and it is possible to calculate their lifetime (based on other values, like the muon lifetime), but that does not answer why they decay.
    Concerning "how": Well, it can be described as interaction with the W boson.
  4. Jan 30, 2013 #3
    In the standard model there are several fundamental forces of nature:

    Strong Nuclear Force
    -Responsible for binding quarks together as well as protons and neutrons​
    Weak Nuclear Force
    -Responsible for all radioactive decay​
    Electromagnetic Force
    -Occurs between everything that has a charge.​

    **Gravity has been debated over the years

    Each of these forces has a corresponding particle known as a gauge boson that is responsible for carrying out those forces. The Strong Nuclear force is carried out by the Gluon, the Weak Nuclear force is carried out by the W and Z bosons (the W boson has positively charged and negatively charged variants,) and the Electromagnetic force is carried out by the Photon.

    In the case of radioactive decay, all radioactive decay occurs as a result of the weak nuclear force. The weak nuclear force is important as it is the only known force that has the potential to change the flavor (characteristics) of a quark. Take, for example, the decay of a proton into a neutron.

    A proton is composed of two up quarks and a down quark and a neutron is composed of two down quarks and an up quark.
    p → n + w+
    The w+ boson then decays into a positron e+ and an electron anti neutrino ̅νe.
    So: p → n + e+ + ̅νe.
    The positron and antineutrino conserve charge. As a result of the interaction with the w+ boson, one of the up quarks changes into a down quark.

    Last edited: Jan 30, 2013
  5. Jan 30, 2013 #4


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    Not all, just beta decays.

    Alpha decays, gamma "decays", proton emission, neutron emission, cluster decays and fission are independent of the weak force.
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