Probing new $U(1)$ gauge symmetries via exotic $Z \to Z' \gamma$ decays

Understand

New $U(1)$ gauge theories involving Standard Model (SM) fermions typically require additional electroweak fermions for anomaly cancellation.

• We study the non-decoupling properties of these new fermions, called anomalons, in the $Z-Z'-\gamma$ vertex function, reviewing the connection between the full model and the effective Wess-Zumino operator.
• We calculate the exotic $Z \to Z' \gamma$ decay width in $U(1)_{B-L}$ and $U(1)_B$ models, where $B$ and $L$ denote the SM baryon and lepton number symmetries.
• For $U(1)_{B-L}$ gauge symmetry, each generation of SM fermions is anomaly free and the exotic $Z \to Z_{BL}' \gamma$ decay width is entirely induced by intragenerational mass splittings.