B-Anomalies from flavorful U(1)' extensions, safely

TL;DR

This paper explores U(1)' gauge extensions of the standard model to explain B-decay anomalies, emphasizing stability, anomaly cancellation, and predictions for future collider experiments.

Contribution

It introduces a new class of anomaly-free U(1)' models with extended fermion and scalar sectors, analyzing their stability and phenomenology up to the Planck scale.

Findings

Identified several anomaly-free models consistent with B-meson decay data.

Predicted Z' bosons with predominantly invisible decays and TeV-scale masses.

Analyzed two-loop running to constrain model parameters and enhance predictivity.

Abstract

$U(1)^\prime$ extensions of the standard model with generation-dependent couplings to quarks and leptons are investigated as an explanation of anomalies in rare $B$-decays, with an emphasis on stability and predictivity up to the Planck scale. To these ends, we introduce three generations of vector-like standard model singlet fermions, an enlarged, flavorful scalar sector, and, possibly, right-handed neutrinos, all suitably charged under the $U(1)^\prime$ gauge interaction. We identify several gauge-anomaly free benchmarks consistent with $B_s$-mixing constraints, with hints for electron-muon universality violation, and the global $b \to s$ fit. We further investigate the complete two-loop running of gauge, Yukawa and quartic couplings up to the Planck scale to constrain low-energy parameters and enhance the predictive power. A characteristic of models is that the $Z^\prime$ with TeV-ish mass predominantly decays to invisibles, i.e. new fermions or neutrinos. $Z^\prime$-production can be studied at a future muon collider. While benchmarks feature predominantly left-handed couplings $C_9^{\mu}$ and $C_{10}^{\mu}$, right-handed ones can be accommodated as well.