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I Semileptonic Lambda baryon decay suppression

  1. Mar 14, 2017 #1
    Hi there,

    I'm currently studying the decay modes of the Lambda baryon (uds).
    According to literature, the decay mode with leptons (e.g. Lambda -> p + e- + anti ve) is suppressed against the decay modes with pions (e.g. Lambda -> p + pi-) by a factor of about 10^-4.
    I was looking for the reason for this suppression, but could'nt find anything. Could anyone explain it to me? I was thinking that it might be due to parity, cause it's not conserved in weak interactions, but I'm not sure whether that's correct.

    Thanks in advance.
     
  2. jcsd
  3. Mar 14, 2017 #2

    Vanadium 50

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    I don't think it's helicity suppression. If that were the case, the semimuonic decay would be much, much larger (about 7800x) than the semielectronic. It's probably 3-body vs. 2-body phase space.
     
  4. Mar 14, 2017 #3

    mfb

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    Shouldn't the phase space favor the three-body decay? Not much energy released in the two-body decay.

    The electron decay is more frequent than the muon decay by a factor of ~5, I can see the phase space factor there.
     
  5. Mar 14, 2017 #4

    Vanadium 50

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    I can't do it in my head, except to note that phase space suppression goes up with increasing numbers of particles, especially when you have a W. The W propagator is trying to drive the e-nu system to high mass, and that bites into phase space. But what I am sure is that it's not helicity suppression, since the electron decay is 5x more frequent than the muon decay and not 1/7800 as frequent.
     
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