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

Can Z decay into a neutral pion?

  1. Jun 7, 2012 #1
    I wondered if the following decay was possible:
    [tex]\Xi^0 \to \Lambda + \pi^0[/tex]

    The only mechanism I can think of is that a strange quark of the Lambda particle emits a Z and becomes a down quark followed by the Z creating a up-antiup pair. But I'm not sure whether the strange to up transition (by emission of Z) is allowed. Neither am I sure about the Z to u-antiu pair is allowed. I know that W can decay into an up and a down quark, but do the Z only interact with neutrinos?
  2. jcsd
  3. Jun 7, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    http://pdglive.lbl.gov/Rsummary.brl?nodein=S023&sub=Yr&return=BXXX030 [Broken], this is the dominant decay mode with >99,5% branching fraction.

    s->u+W, W->anti-u+d, combine the d with the existing u+s to form the lambda, and use the u anti-u for the pion.

    The Z can interact with quarks, but in order to change their flavor with Z emission you need loop processes.
    Last edited by a moderator: May 6, 2017
  4. Jun 7, 2012 #3
    Thank you for the reply! So the Z can change flavour anyway? I did some research and found this page on hyperphysics which claimed that a Z boson could not change the flavour of quarks.

    Last edited by a moderator: May 6, 2017
  5. Jun 7, 2012 #4
    It is true that a Z cannot change flavour - there are no so called Flavour Changing Neutral Currents (FCNC) - at tree level (i.e. without loops). A source of confusion might be that FCNC processes are permitted at higher order, that is, when loops are included. See the picture at Wikipedia: http://en.wikipedia.org/wiki/Flavor-changing_neutral_current

    A Z boson will however, never be able to change the flavour of a quark "on its own". So decays of the type s->Z+d are not permitted in the Standard Model.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook