•Calculation of the amplitude

$ConstantIsoIndices = {} ;

amplFC = (CreateFCAmp[mesontreeinsert, AmplitudeLevel -> Classes, Sum -> False, EqualMasses -> True] // MomentumCombine) /. {p3 + p4 -> -p1, -p3 - p4 -> p1} // SUNReduce[#, FullReduce -> True] & // ExpandScalarProduct // Simplify

{(5 e^( ) (p _ 3^μ _ 1 - p _ 4^μ _ 1) µ _ μ _ 1(p _ 1) f _ (3 i _ 1 i _ 2)^(2))/(48 π^4 (f _ π^(ó  ))^2 (q _ 1^2 - (m _ π^(ó  ))^2)), -(e^( ) (p _ 1^μ _ 1 - 2 q _ 1^μ _ 1) µ _ μ _ 1(p _ 1) (p _ 1 · p _ 3 - p _ 1 · p _ 4 - 2 p _ 3 · q _ 1 + 2 p _ 4 · q _ 1) f _ (3 i _ 1 i _ 2)^(2))/(32 π^4 (f _ π^(ó  ))^2 (q _ 1^2 - (m _ π^(ó  ))^2) . ((q _ 1 - p _ 1)^2 - (m _ π^(ó  ))^2))}

Converted by Mathematica  (July 10, 2003)