Date: 06/11/15-11:20:11 PM Z

Hi,

it depends on what you want to do with H.
First of all, FeynCalc doesn't deal with explicit components of
vectors and spinors. If you are working on the level of amplitudes,
then

h = Contract[SpinorUBar[p2, m2].GA[mu].SpinorU[p1, m1]
PolarizationVector[q, mu]]

is the simplest form you can get. Of course you can insert
explicit components using Mathematica and do the multiplication
of spinors and Dirac matrices, but for that you don't really need
FeynCalc. On the other hand, if you want to compute matrix element
squared, then you cold do say

h2 = FermionSpinSum[h ComplexConjugate[h]] // Tr

and then replace scalar products with some explicit values that are
given by the kinematics you choose,like

h2 /. {FCI[SP[p1, p2]] -> E1*E2 - p1v*p2v*Cos[theta]}

Cheers,

Am 11.06.2015 um 17:06 schrieb dinesh:
> I am learning feyncalc. I have one problem;
> Two spinors are defined as :
> \bar_U1(p1,m1)=(1,0,0,0)
> \bar_U2(p2,m2)=(0,1,0,p2/m2)
> and epsilon^mu = (q0,0,0,q)
> then how can i write H = (\bar_U2(p2,m2)(GA[mu])U1(p1,m1))_mu epsilon^mu.