•PP

At this point, please reload FeynCalc.

QuantumField[Particle[PseudoScalar[0], ___], ___, ExplicitSUNIndex[0], ___][_] := 0 ;

lag = Lagrangian[ChPT3[4]] /. CouplingConstant[ChPT3[4], 1 | 2 | 3 | 4 | 5 | 9 | 10 | 11, ___][___] :> 0

L _ 7^( ) ((< χ '6 ÷„^† > - < ÷„ '6 χ^† >) '6 (< χ '6 ÷„^† > - < ÷„ '6 χ^† >)) + L _ 6^( ) ((< ÷„ '6 χ^† > + < χ '6 ÷„^† >) '6 (< ÷„ '6 χ^† > + < χ '6 ÷„^† >)) + H _ 2^( ) < χ^† '6 χ > + L _ 8^( ) (< ÷„ '6 χ^† '6 ÷„ '6 χ^† > + < χ '6 ÷„^† '6 χ '6 ÷„^† >)

ll = ArgumentsSupply[<br /> lag, x, RenormalizationState[0], ExpansionOrder -> 0, DropOrder -> 0, DiagonalToU -> True] ;

lll = DiscardTerms[ll, Retain -> {Particle[PseudoScalar[0] , RenormalizationState[0]] -> 2}, CommutatorReduce -> True, Method -> Expand] // Simplify

4 (H _ 2^( ) - 2 L _ 8^( )) (!, _ 0^( ))^2 < Overscript[p^( ), ->] · Overscript[σ, ->] '6 Overscript[p^( ), ->] · Overscript[σ, ->] >

llle = ExpandU[lll, CommutatorReduce -> True] // Simplify

8 (H _ 2^( ) - 2 L _ 8^( )) Overscript[p^( ), ->] · Overscript[p^( ), ->] (!, _ 0^( ))^2

$IsoIndicesCounter = 0 ;

llll = llle // IsoIndicesSupply // Simplify

8 (H _ 2^( ) - 2 L _ 8^( )) (p^( )^i _ 1 '6 p^( )^i _ 1) (!, _ 0^( ))^2

fields = {QuantumField[Particle[PseudoScalar[0], RenormalizationState[0]], SUNIndex[I1]][p1], QuantumField[Particle[PseudoScalar[0], RenormalizationState[0]], SUNIndex[I2]][p2]}

{p^( )^I _ 1, p^( )^I _ 2}

amp4 = FeynRule[llll, fields] // Simplify // SUNReduce // IndicesCleanup // Simplify

-16 i (2 L _ 8^( ) - H _ 2^( )) (!, _ 0^( ))^2 δ _ (I _ 1 I _ 2)^(3)

Converted by Mathematica  (July 10, 2003)