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Difference between 2to2 interactions

  1. Jun 8, 2014 #1


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    What is the difference between these interactions?
    [itex] a+b \rightarrow c+d[/itex]
    [itex] b+a \rightarrow d+c [/itex]

    I was reading the "State-of-the-art formulas for helicity amplitude calculation and all that" ver 2.4, part Ia. - Spherical-vector method for helicity amplitudes (Formalism), by Ken-Ichi Hikasa.
    In the discrete symmetry and helicity amplitudes sector (pg 5) he gives different invariant matrices [itex]M[/itex] forms for these two above.
  2. jcsd
  3. Jun 9, 2014 #2


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    Are you SURE there is no difference between the notation in the two equations, ONLY the ordering? (such as a helicity index change?) He doesn't reference two different diagrams? (s and t channel?)
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