By: ValentinHirschi <valentin.hirschi@gmail.com>
lower UFO Epsilon with the UFO normalization
UFO's Lorentz Epsilon is the real Levi-Civita tensor eps^{mu nu rho sigma}
with eps^{0123} = -1 (ALOHA's representation, matching FeynRules), so
Tr[g5 g^mu g^nu g^rho g^sigma] = 4i Epsilon(mu,nu,rho,sigma) for the same
g5 = diag(-1,-1,1,1). Idenso's spenso::epsilon is normalized by its trace
rule Tr[...] = 4 eps, i.e. eps^{0123} = -i. Lowering Epsilon unchanged
therefore multiplied every CP-odd vertex by i relative to MadGraph. Lower
it as -i spenso::epsilon and require the four UFO indices.
A test lowers the UFO trace Gamma5 Gamma(1) Gamma(2) Gamma(3) Gamma(4) and
4i Epsilon(1,2,3,4); after Idenso's simplification they agree only with the
factor.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>