Use ScalarProduct[pa,k ] = 1
rolfm@gluon:~$ math
Mathematica 6.0 for Linux x86 (64-bit)
Copyright 1988-2007 Wolfram Research, Inc.
In[1]:= !!t.m
<<HighEnergyPhysics`fc`;
ScalarProduct[pa,k]=1;
Lmunu = FV[l, \[Mu]]*FV[k, \[Nu]] + FV[l, \[Nu]]*FV[k, \[Mu]];
Wmunu = FV[pa, \[Mu]]*FV[pa, \[Nu]];
Contract[Lmunu*Wmunu] // FCE // InputForm
In[1]:= <<t.m
Out[1]//InputForm= 2*SP[l, pa]
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Rolf Mertig
GluonVision GmbH
Berlin, Germany
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