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Homework Statement
(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? [/B]
Homework Equations
The Attempt at a Solution
Part(a)[/B]
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?