Extra U(1), effective operators, anomalies and dark matter

Understand

A general analysis is performed on the dimension-six operators mixing an almost hidden Z' to the Standard Model (SM), when the Z' communicates with the SM via heavy mediators.

• These are fermions charged under both Z' and the SM, while all SM fermions are neutral under Z'.
• We classify the operators as a function of the gauge anomalies behaviour of mediators and explicitly compute the dimension-six operators coupling Z' to gluons, generated at one-loop by chiral but anomaly-free, sets of fermion mediators.
• We prove that only one operator contribute to the couplings between Z' charged matter and on-shell gluons.