Name: Francesco Date: 07/02/16-11:03:08 AM Z

Ok, I installed the new version. Thank you very much!

Anyway, I think it should be easier splitting the vertices using a heavy vector.

So I followed your suggestion and I created a model in FeynRules with a auxiliary particles
 V[5] == {
    ClassName -> AUX,
    SelfConjugate -> True,
    Mass -> {MAUX, Internal},
    Width -> 0,
    PropagatorLabel -> “aux”,
    PropagatorType -> D,
    PropagatorArrow -> None,
    ParticleName -> “Auxiliary”
  },

 and the vertex

Lff := Block[{mu},
  ExpandIndices[(
    QLbar.Ga[mu].QL AUX[mu]),
  FlavorExpand->{SU2W,SU2D}]/.{CKM[a_,b_] Conjugate[CKM[a_,c_]]->IndexDelta[b,c], CKM[b_,a_] Conjugate[CKM[c_,a_]]->IndexDelta[b,c]}];

Here you find the FeynArts output https://www.dropbox.com/sh/hm77oyedcb3p055/AABzBlEPZvcPjAstjoclCR3ya?dl=0 (the model name is model1)

When I try to create the feynman amplitude, the kernel always crashes and I don’t understand why (see here https://s31.postimg.org/f8p6xy53v/Screen_Shot_2016_07_02_at_11_00_51_AM.png )

what do you think? Thank you very much for your work!