(*********************** Program VacPol.m **************************)
(*
 Version compatible with FeynCalc 9.2.0

 Date: 01/06/2017
 Author: Jorge C. Romao
 email: jorge.romao@tecnico.ulisboa.pt
*)
 
(* First input FeynCalc *)
(* Uncomment below if you want to call from this program. If open a new
   mathematica notebook and load FeynCalc from there you should not load
   it again
*)
(*
<< FeynCalc`
*)

(* Now write the numerator of the Feynman diagram. We define the 
   constant

       C=alpha/(4 pi)
 
   I also use the FCE notation available since FeynCalc 6. See manual
   for explanations.
 
*)

num:= - C Tr[GA[mu] . (GS[q] + m) . GA[nu] .  (GS[q]+GS[k]+m)]
  
(* Set some Options. This changed from previous versions *)

SetOptions[PaVeReduce,A0ToB0->True];
$LimitTo4 = True;
  
(* Define the amplitude *)

amp:=num * FeynAmpDenominator[PropagatorDenominator[q+k,m], \
                             PropagatorDenominator[q,m]]

(* Calculate the result *)

res:=(-I / Pi^2) OneLoop[q,amp] 
ans=PaVeReduce[res,PaVeAutoReduce->True] //Simplify 

(******************** End of Program VacPol.m **********************)
