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

Xi decay quarks conserved but flavour not conserved

  1. Nov 13, 2012 #1

    I have been looking into particle physics and i came across this question but i can not find the answer,

    the quetsion is as follows:

    the xi particle decays into the following
    [itex]\Xi -> \wedge + \Pi^{-}[/itex]
    dds -> sud + [itex]\overline{u}d [/itex]
    the quark numbers are conserved but the flavours are not conserved.

    I cannot understand why the flavours are not conserved. Can anyone help me?
  2. jcsd
  3. Nov 13, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Where does that come from?
    Looks conserved to me.

    The long lifetime (~10-10s) is suspicious.
  4. Nov 13, 2012 #3
    It says on it why isnt it conserved and is it decayed by strong or weak forces.
    I would say weak because flavours are not conserved but by looking at it, it seems to be conserved
  5. Nov 13, 2012 #4


    User Avatar
    2017 Award

    Staff: Mentor

    Well, it is easy to draw a diagram for the strong interaction.

    The long lifetime indicates that those diagrams are problematic in terms of parity, or cancel each other partially, or something else.

    Edit @Bill_K's post: Oh, that explains everything. And ##\Sigma^-## with dds is too light to decay into ##\Lambda + \pi##

    Attached Files:

    Last edited: Nov 13, 2012
  6. Nov 13, 2012 #5


    User Avatar
    Science Advisor

    The Ξ- (aka cascade particle) is not dds, it's dss. The decay is weak because it does not conserve strangeness.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook