Abstract
Abstract Extensions of the Standard Model with an extra U′(1) abelian group generically generate terms coming from loops of heavy fermions, leading to three gauge boson couplings, in particular Z′Zγ. We show that WMAP data constrains the gauge coupling of the group g D to values comparable with the electro-weak ones, rather independently of the mass of Z′. Moreover, the model predicts a monochromatic γ-ray line which can fit a 130 GeV signal at the FERMI telescope for natural values of the Chern-Simons terms and a dark matter mass around 144.5 GeV.
Highlights
The Chern-Simons terms, usually related to the mechanism of gauge anomaly cancelation
We have discussed an extension of the Standard Model with an extra U′(1) abelian group, where a three gauge boson couplings Z′Zγ is generated from Chern-Simons terms
We studied the different scenarios allowed by this model, for different values of the mass parameters, under the hypothesis that the dark matter candidate is charged only under the extra abelian group
Summary
Triangle gauge anomalies cancelation can occur by a consistent field theory content or by cancelation of triangle loops by axionic couplings and Chern-Simons terms, via the string theory Green-Schwarz mechanism. At low-energy, remnants of the anomaly cancelation can lead to generalized Chern-Simon terms [59,60,61] containing new three gauge boson couplings. Where CS stands for Chern-Simons, Fρ′σ = ∂ρZσ′ − ∂σZρ′ and (α1,α2) are the coefficients (computable exactly once given the fermionic content of the model) generated by the triangle diagrams depicted in figure 1. We notice here that CS terms are generic in string constructions, where their gauge non-invariance is compensated by axionic couplings and triangle loops of light fermions charged under the extra U(1)′. Depending on the mass of ψ, we describe in detail each possibility
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