Difference between 2to2 interactions

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

    Hepth 508
    Gold Member

    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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