Accounting a antisymmetrization of amplitude

b-term is not zero.  In Majorana basis we have

  b  'e+' gamma_0  gamma_5 'e+'

   In Majorana basis  gamma_0^T =-gamma_0    and gamma_5^T=-gamma_5. Then

(gamma_0  gamma_5)^T =   gamma_5  gamma_0  = - gamma_0  gamma_5

So we have antisymmetric  matrix between  'e+' and  'e+'  in b term. It
is not a zero term.

Best

    Alexander Pukhov

On 15.04.2019 19:32, Ekaterina wrote:
> New question #680273 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/680273
>
> Hello, dear CalcHEP experts!
> We have a number of questions about how to take into account the identity of particles in the final state in CalcHEP.
> We consider the decay of a scalar particle X into two identical fermions (X -> e + e +).For the introduction of a new model, we used LanEP. There we built the Lagrangian we needed and imported a new model into CalcHEP.
> We want to get the squares of the matrix elements in order to compare with those that we obtained earlier.
> However, judging by the square of the matrix element, which we obtain using CalcHEP, it seems that the antisymmetrization of amplitude over identical fermions in the final state is not taken into account.
> The amplitude of the X-> e + e + process was determined manually . If you make this calculation manually, then the square of the matrix element is proportional to a ^ 2 (due to the interference of two terms in the matrix element). However, the result of the calculation in CalcHEP turned out to be proportional (a ^ 2 + b ^ 2), which corresponds to one term in the matrix element (that is, the absence of antisymmetrization of amplitude over finite identical fermions).
> Our question is whether it is possible to take the above into account (antisymmetrization of amplitude)?
>
> Our model is as follows
>
> model DMSM/1.
> scalar '~x1'/'~X1': ('X1', mass MX1=100, pdg 9000005).
> spinor 'e-'/'e+' : ('Electron', pdg 11 ).
> vector A/A : ('Photon',gauge).
> parameter a1=1,b1=1,EE = 0.31333 : 'Electromagnetic coupling constant (<->1/128)'.
>
> lterm '~X1'*anti(cc('e-'))*(a1 + b1*gamma5)*'e+' + AddHermConj.
> lterm EE*'e-'*gamma*'e+'*A.
>
>
> Thank!
> Sincerely, Ekaterina!
>