Searching for the Leptophilic Gauge Boson Z$_{l}$ at Future $e^{+}e^{-}$ Colliders

TL;DR

This paper evaluates the potential of future electron-positron colliders to discover the leptophilic gauge boson Z extsubscript{l} by analyzing muon pair production, considering realistic collider effects and comparing different collider types.

Contribution

It provides a comprehensive analysis of Z extsubscript{l} discovery prospects at various future colliders, highlighting their complementary sensitivities and extending the search reach into higher energies.

Findings

Circular colliders can detect very small couplings (~10^{-4}).

Linear colliders can probe Z extsubscript{l} at TeV energies.

The analysis includes realistic effects like initial state radiation and beamstrahlung.

Abstract

We study the discovery prospects of the leptophilic photon Z\_l, a hypothetical gauge boson beyond the Standard Model, at future electron-positron colliders. Our analysis is based on the process e+e- -> mu+mu- and consistently includes realistic effects such as initial state radiation and beamstrahlung. Using the benchmark parameters of FCC-ee, CEPC, ILC, and CLIC, we demonstrate the complementarity of circular and linear colliders: circular machines achieve excellent sensitivity to very small couplings, down to g\_l ~ 10^{-4}, while high-energy linear colliders extend the search reach into the TeV domain.