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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,

Vladyslav

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.
*

*> Please help me .
*

*>
*

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