1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How many W mesons required?

  1. Nov 16, 2007 #1
    1. The problem statement, all variables and given/known data
    The decay
    [tex]D^{+} \rightarrow D^{0} \pi^{+}[/tex]
    is not possible via a weak interaction which involves one virtual W+ meson. How many virtual W mesons are required?

    2. Relevant equations
    D0 has quark content c-ubar
    Pi+ has quark content u-dbar
    I'm not sure what D+ has...

    3. The attempt at a solution
    Assuming D+ has c-dbar...
    how do you determine whether a virtual meson is involved or not and how many? Is it energy based?
  2. jcsd
  3. Nov 16, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    Last edited: Nov 16, 2007
  4. Nov 16, 2007 #3
    thanks very much!
    so D+ has c-dbar...
    D+ = 1869MeV
    D- = 1865MeV
    pi+ = 139.6MeV

    So that means both a W+ and a W- boson are required to keep the charge at +1 on both sides? And have energy greater than 139.6-5?
  5. Nov 16, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper

    Even though you had more W bosons involved, i say that it violates energy.
  6. Nov 16, 2007 #5
    okay, thanks... so a trick question? An even number of bosons would be required to conserve charge, but energy will never be conserved so it can't happen...
  7. Nov 17, 2007 #6


    User Avatar
    Science Advisor
    Homework Helper

    Hmm ONE W+ boson also conserve charge.

    In each vertex, charge, lepton number etc are conserved.

    imagine the following:
    In the D+ , the W+ turns the d-bar quark to an u-bar quark, and latter decays into something.

    The thing is that you have less mass on the RHS of the eq, W+ can decay into one pion + meson. so there is no problem besides energy.

    I THINK that you have made a misstake, that it should be the [tex] D^x _S [/tex] Meson instead, then you have more mass (maybe correct mass for it to be allowed energetically). I might be wrong, but that is one desperate way =)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook