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Psi meson decay modes

  1. Apr 20, 2015 #1
    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?


    2013_B4_Q1.png
    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^-##:
    2013_B4_Q1_2.png

    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^{-}##
    2013_B4_Q1_3.png
    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. jcsd
  3. Apr 22, 2015 #2
  4. Apr 25, 2015 #3
    Important elements?
     
  5. Apr 26, 2015 #4
    What are the important elements in a detector?
     
  6. Apr 30, 2015 #5
    bumpppppp
     
  7. May 4, 2015 #6
    what things that are important make a reactor?
     
  8. May 7, 2015 #7
    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##?
     
  9. May 10, 2015 #8
    bumpp part (f)
     
  10. May 14, 2015 #9
    bump on part (f) Centre of mass energy?
     
  11. May 16, 2015 #10
    bumpp on part (f)
     
  12. May 18, 2015 #11
    bump on (f): Centre of Mass Energy
     
  13. May 22, 2015 #12
    bumpp - Centre of mass energy?
     
  14. May 23, 2015 #13
    bumpp on part (f)
     
  15. May 25, 2015 #14
    bumpp - is my centre of mass energy right? Part (f)
     
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