What is the difference between these interactions?(adsbygoogle = window.adsbygoogle || []).push({});

[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.

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# Difference between 2to2 interactions

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