# Psi meson decay modes

Tags:
1. Apr 20, 2015

### unscientific

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

(a) Explain spin and parity of mesons
(b) State their quark content
(c) Draw a feynman diagram of J/psi decay
(d) Why doesn't $\chi$ undergo leptonic decay?
(e) What is the minimum centre of mass?

2. Relevant equations

3. The attempt at a solution

Part(a)

Spin is either 0 (singlet) or 1 (tripplet) for a pair of fermions. Parity is given by $(-1)^{L+1}$.

Part(b)
Quark content is charm and anti-charm hadron $c\bar c$. For $1^-$ states, $L=0, S=1, J=1$. For $0^+$ states, $L=1, S=1, J=0$ through spin-orbit coupling. For $1^+$ states, $L=1, S=0, J=1$. For $2^+$ states, $L=S=1, J=2$.

Part(c)
EM decay of J\Psi to either $e^+e^-$ or $\mu^+ \mu^-$:

Part (d)
Previously, it was kinematically impossible for strong interactions. Now that the mass of excited $\psi^{''}$ is higher, there is a direct possibility of decay in strong interaction to $D^+D^-$. Strong interactions are preferred over weak interactions.

Part (e)
Why doesn't $\chi$ decay to pairs of charged leptons?
Possible reaction for $\psi^{'} \rightarrow \chi_0 + \mu^{+} + \mu^{-}$ or $\psi^{'} \rightarrow \chi_0 + e^{+} + e^{-}$

For decay to $\chi_1$ and $\chi_2$ only $e^{-}e^{+}$ pairs are allowed.

Part (f)
I suppose minimum mass is $m_{\chi2} + 2m_e = 3557 MeV$.
What are the important elements?

2. Apr 22, 2015

### unscientific

bumpp

3. Apr 25, 2015

### unscientific

Important elements?

4. Apr 26, 2015

### unscientific

What are the important elements in a detector?

5. Apr 30, 2015

bumpppppp

6. May 4, 2015

### unscientific

what things that are important make a reactor?

7. May 7, 2015

### unscientific

For part (f) : Isn't the minimum centre of mass energy for $\chi$ decays to be observed simply the mass of $m_\chi = 3415 MeV/c^2$?

8. May 10, 2015

### unscientific

bumpp part (f)

9. May 14, 2015

### unscientific

bump on part (f) Centre of mass energy?

10. May 16, 2015

### unscientific

bumpp on part (f)

11. May 18, 2015

### unscientific

bump on (f): Centre of Mass Energy

12. May 22, 2015

### unscientific

bumpp - Centre of mass energy?

13. May 23, 2015

### unscientific

bumpp on part (f)

14. May 25, 2015

### unscientific

bumpp - is my centre of mass energy right? Part (f)