•Calculation and reduction of the amplitude

ampp4 = (CreateFCAmp[mesontreeinsert, AmplitudeLevel -> Classes][[1]] // SUNReduce) /. D :> Sequence[] ;

ampl4 = FullSimplify /@ ((FullSimplify /@ Collect[ampp4 /. ParticleMass[Pion, RenormalizationState[0]] -> ParticleMass[Pion, RenormalizationState[1]] // MandelstamReduce[#, Cancel -> None] &, {_SU2Delta, _CouplingConstant}]) /. manrules)

1/(3 (f _ π^(ó  ))^4) (4 (4 (6 L _ 2^( ) + 3 L _ 3^( ) - 10 L _ 4^( ) - 5 L _ 5^( ) + 8 L _ 6^( ) + 4 L _ 8^( )) (m _ π^(ó  r ))^4 - 12 t (L _ 2^( ) + L _ 3^( ) - 2 L _ 4^( ) - L _ 5^( )) (m _ π^(ó  r ))^2 + 6 L _ 1^( ) (t - 2 (m _ π^(ó  r ))^2)^2 + 3 (t^2 - 2 s u) L _ 2^( ) + 3 t^2 L _ 3^( )) δ _ (i _ 1 i _ 4)^(2) δ _ (i _ 2 i _ 3)^(2)) + 1/(3 (f _ π^(ó  ))^4) (4 (4 (6 L _ 2^( ) + 3 L _ 3^( ) - 10 L _ 4^( ) - 5 L _ 5^( ) + 8 L _ 6^( ) + 4 L _ 8^( )) (m _ π^(ó  r ))^4 - 12 u (L _ 2^( ) + L _ 3^( ) - 2 L _ 4^( ) - L _ 5^( )) (m _ π^(ó  r ))^2 + 6 L _ 1^( ) (u - 2 (m _ π^(ó  r ))^2)^2 + (3 u^2 - 6 s t) L _ 2^( ) + 3 u^2 L _ 3^( )) δ _ (i _ 1 i _ 3)^(2) δ _ (i _ 2 i _ 4)^(2)) + 1/(3 (f _ π^(ó  ))^4) (4 (4 (6 L _ 2^( ) + 3 L _ 3^( ) - 10 L _ 4^( ) - 5 L _ 5^( ) + 8 L _ 6^( ) + 4 L _ 8^( )) (m _ π^(ó  r ))^4 - 12 s (L _ 2^( ) + L _ 3^( ) - 2 L _ 4^( ) - L _ 5^( )) (m _ π^(ó  r ))^2 + 6 L _ 1^( ) (s - 2 (m _ π^(ó  r ))^2)^2 + 3 (s^2 - 2 t u) L _ 2^( ) + 3 s^2 L _ 3^( )) δ _ (i _ 1 i _ 2)^(2) δ _ (i _ 3 i _ 4)^(2))

Converted by Mathematica  (July 10, 2003)