Solving the electron and muon g-2 anomalies in Z′ models

• Published in: The European physical journal. C, Particles and fields Vol. 81; no. 12
• Main Authors: Bodas, Arushi, Coy, Rupert, King, Simon J. D.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-12-2021; Springer Nature B.V
• Subjects: Anomalies; Astronomy; Astrophysics and Cosmology; Cesium; Couplings; Elementary Particles; Experiments; Flavor (particle physics); Hadrons; Heavy Ions; Leptons; Measurement Science and Instrumentation; Muons; Neutrinos; Nuclear Energy; Nuclear Physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; Rubidium; Standard model (particle physics); String Theory
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-021-09850-x

We consider simultaneous explanations of the electron and muon
g
-
2
anomalies through a single
Z
′
of a
U
(
1
)
′
extension to the Standard Model (SM). We first perform a model-independent analysis of the viable flavour-dependent
Z
′
couplings to leptons, which are subject to various strict experimental constraints. We show that only a narrow region of parameter space with an MeV-scale
Z
′
can account for the two anomalies. Following the conclusions of this analysis, we then explore the ability of different classes of
Z
′
models to realise these couplings, including the SM
+
U
(
1
)
′
, the
N
-Higgs Doublet Model
+
U
(
1
)
′
, and a Froggatt–Nielsen style scenario. In each case, the necessary combination of couplings cannot be obtained, owing to additional relations between the
Z
′
couplings to charged leptons and neutrinos induced by the gauge structure, and to the stringency of neutrino scattering bounds. Hence, we conclude that no
U
(
1
)
′
extension can resolve both anomalies unless other new fields are also introduced. While most of our study assumes the Caesium
(
g
-
2
)
e
measurement, our findings in fact also hold in the case of the Rubidium measurement, despite the tension between the two.