Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

What is Dalitz decay?

I know there are Dalitz $\pi^0 \to e^+ + e^- + \gamma$ decay, $w \to \pi^0 + e^+ + e^-$ decay, may be more. But is there a rule to say which decay is Dalitz and which is not?

Is there a rule to say which particle can decay by Dalitz decay and which does not?

share|improve this question
    
I've found more examples: $\eta \to e^+ + e^- + \gamma$ decay, $\pi^0 \to e^+ + e^-+ e^+ + e^-$, $K_L^0 \to \mu^+ + \mu^- + \gamma$ and it seems to me that the any 3 and 4 particle decays are called Dalitz decay, since Dalitz plot can be applied to analyze them. –  klm123 Aug 12 '12 at 23:39
    
that first decay is not allowed by four-momenta conservation, you cannot decay one light-like particle unless its an intermediate stage of a larger decay, it needs to be either zero or two. –  user56771 Aug 12 '12 at 23:49
    
which first? $\eta$? –  klm123 Aug 12 '12 at 23:52
    
Presumably @user56771 means that there is no tree-level diagram for it. These decays certainly happen. The PDG gives the $\pi^0$ example a branching ratio of about 1% of all neutral pion decays. –  dmckee Aug 13 '12 at 1:39

2 Answers 2

up vote 2 down vote accepted

After a really brief cursory review of the literature, I think that a Dalitz decay is a meson decay that involves two leptons in the final state, plus a photon. A double Dalitz decay has four leptons in the final state: see this paper and this paper for examples of the usage. The Dalitz decay is when a virtual photon from 2 photon decay of $\pi_0$ internally converts to a real lepton pair before it gets too far, and analogous thing for other meson or Higgs processes (two electrons from an internal photon conversion, plus a neutral object).

I guess that the usage comes from the kinematic decay product phase space is described by a Dalitz plot, hence the name. I don't think it's anything deep.

share|improve this answer
    
Sorry for my pedantry, but could you give me a reference on the definition in a reliable book? What you told was exactly my previous assumption, but I have to be sure. –  klm123 Aug 13 '12 at 3:15
    
@kim123: I wasn't sure about the previous answer, I just thought of the first thing that came to mind honestly, and I couldn't think of anything else. But I googled for usage, and it always is the decay of a meson into two leptons and something else. A double-Dalitz decay is into four leptons, so that establishes that the usage is for 2 lepton final states. The term Dalitz decay itself is never used without a meson as far as I saw in the search, so I changed my answer. Thanks for keeping me honest, my original answer was probably totally wrong. –  Ron Maimon Aug 13 '12 at 4:12

A particle's Dalitz decay means the particle decays to a massless gauge boson and two massless fermions. You can find this definition in 1308.0422.

share|improve this answer
1  
While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. –  Dimensio1n0 Aug 25 '13 at 8:36

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.