Probing the $L_\mu-L_\tau$ gauge boson at electron colliders

TL;DR

This paper explores the potential to detect a $U(1)_{L___ au}$ gauge boson at electron colliders through kinetic mixing effects, proposing experimental searches and analyzing sensitivity to new parameter space.

Contribution

It introduces a novel approach to search for the $Z'$ gauge boson via monophoton signatures at electron colliders, considering loop-induced kinetic mixing effects.

Findings

Electron colliders can probe previously unexplored $Z'$ parameter space.

Future STCF experiments can exclude the muon magnetic moment anomaly region for $Z'$ mass below 5 GeV.

Sensitivity to $g_{Z'}$ can reach as low as $4.2\times 10^{-5}$ at 2 GeV.

Abstract

We investigate the minimal $U(1)_{L_\mu-L_\tau}$ model with extra heavy vector-like leptons or charged scalars. By studying the kinetic mixing between $U(1)_{L_\mu-L_\tau}$ gauge boson $Z^\prime$ and standard model photon, which is absent at tree level and will arise at one loop level due to $\mu$, $\tau$ and new heavy charged leptons or scalars, the interesting behavior is shown. It can provide possibility for visible signatures of new heavy particles. We propose to search for $Z^\prime$ at electron collider experiments, such as Belle II, BESIII and future Super Tau Charm Factory (STCF), using the monophoton final state. The parameter space of $Z^\prime$ is probed, and scanned by its gauge coupling constant $g_{Z^\prime}$ and mass $m_{Z^\prime}$. We find that electron colliders have sensitivity to the previously unexplored parameter space for $Z^\prime$ with MeV-GeV mass. Future STCF experiments with $\sqrt s=2-7$ GeV can exclude the anomalous muon magnetic moment favored area when $m_{Z^\prime}<5$ GeV with the luminosity of 30 ab$^{-1}$. For $m_{Z^\prime} < 2m_\mu$, $g_{Z^\prime}$ can be down to $4.2\times 10^{-5}$ at 2 GeV STCF.