# Homework Help: Particle Interaction

1. Feb 6, 2008

### neelakash

1. The problem statement, all variables and given/known data

I have already solved almost all of the following questions.Just want to check them and improve reasoning.So, please do not blame me for asking you to do it for me.

Check if the following interactions are possible or forbidden and indicate the interactions when applicable.

2. Relevant equations

$$\ Q$$---charge conservation test
$$\ L$$---Lecton number test
$$\ B$$---Baryon number test
$$\ I_3$$---Isospin test
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Isospin $$\ I_3$$ is violated in EM and Weak interaction
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Strangeness $$\ S$$ is violated $$\Delta$$$$\ S=1$$ in weak interaction
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3. The attempt at a solution

(i) $$\pi^-\ + \ p \rightarrow\ k^0 \ + \Lambda^0$$---Allowed [Q,B,S,I_3---all satisfied---Strong interaction]

(ii) $$\pi^-\ + \ p \rightarrow\ k^0 \ + \Sigma^0$$---Allowed [Q,B,S,I_3---all satisfied---Strong interaction]

[(I am doubtful if I have correctly said that they are strong interaction.Are they?]

(iii) $$\Sigma^0\rightarrow\Lambda^0\ + \gamma$$

---Allowed [Q,B,S,I_3---all satisfied---strong interaction]

(iv) $$\Sigma^+\rightarrow\ p \ + \gamma$$

---Not Allowed [I_3 non-conservation and ∆S=1---it looks that this might be allowed via weak interaction.But I found in book that it is not allowed. Is it bacause there is no Leptons?]

(v) $$\pi^0\rightarrow\gamma\ + \gamma$$

---Allowed.[I suspect it is EM interaction.But any strong evidence?]

(vi) $$\ K^+ \rightarrow\pi^0\ + \mu^+\ + \nu_\mu$$

---Allowed[Q,L,B satisfied---∆S=1--weak interaction because nutrino is involved only in weak interaction].

(vii) $$\Xi^-\rightarrow\Lambda^0\ + \pi^-$$

---Allowed[Q,B satisfied.∆S=1 as in weak interaction]

(viii) $$\Xi^-\rightarrow\ n \ + \pi^-$$

---Not allowed [∆S=2---never allowed in any interaction]

(ix) $$\Lambda^0\rightarrow\pi^+\ + \pi^-$$

---Not Allowed.[B,S non-conservation]

(x) $$\ n \rightarrow\ e^+ \ + \ e^-$$

---Not allowed.B non-conservation and mass non-conservation (n,e are stable particles).

Last edited: Feb 6, 2008