\begin{document}$ Z_\ell $\end{document} at future \begin{document}$ e^+e^- $\end{document} colliders, focusing on a comparative study of the Circular Electron–Positron Collider (CEPC) and the International Linear Collider (ILC). Such a state naturally arises from an additional \begin{document}$ U(1)'_\ell $\end{document} gauge symmetry, under which quarks remain neutral while all leptons carry a universal charge, motivated by neutrino oscillations and scenarios of physics beyond the Standard Model. As a clean benchmark, we study the process \begin{document}$ e^+e^- \to \mu^+\mu^- $\end{document}, including realistic effects of initial-state radiation and beamstrahlung. Our results indicate that the CEPC, with its very high luminosity at \begin{document}$ \sqrt{s}=240 $\end{document} GeV, can probe couplings down to \begin{document}$ g_\ell \approx 10^{-3} $\end{document} for \begin{document}$ Z_\ell $\end{document} masses up to about 220 GeV. The ILC extends the sensitivity to heavier states in the multi-hundred GeV range through its higher \begin{document}$ \sqrt{s} $\end{document} stages. These findings demonstrate the strong complementarity of circular and linear colliders in exploring purely leptophilic interactions."> Discovery prospects for a leptophilic gauge boson <i>Z<sub>ℓ</sub></i> at CEPC and ILC -
  • [1]

    S. Navaset al. (Particle Data Group), Phys. Rev. D110, 030001 (2024)

  • [2]

    Y. Fukudaet al. (Super-Kamiokande Collaboration), Phys. Rev. Lett.81, 1562 (1998)

  • [3]

    Q. R. Ahmadet al. (SNO Collaboration), Phys. Rev. Lett.89, 011301 (2002)

  • [4]

    T. D. Lee and C. N. Yang, Phys. Rev.98, 1501 (1955)

  • [5]

    L. B. Okun, Sov. Phys. JETP29, 1 (1969)

  • [6]

    P. Fayet, Phys. Lett. B95, 285 (1980)

  • [7]

    P. Langacker, Rev. Mod. Phys.81, 1199 (2009)

  • [8]

    J. Heeck and W. Rodejohann, Phys. Rev. D84, 075007 (2011)

  • [9]

    W. Altmannshofer, C. Frugiuele, and R. Harnik, JHEP12, 180 (2014)

  • [10]

    M. Bauer and M. Neubert, Phys. Rev. Lett.120, 141802 (2018)

  • [11]

    CEPC Study Group, (2018), arXiv: 1809.00285

  • [12]

    T. Behnkeet al., (2013), arXiv: 1306.6327

  • [13]

    L. B. Okun, Sov. Phys. Usp.12, 427 (1970)

  • [14]

    B. Holdom, Phys. Lett. B166, 196 (1986)

  • [15]

    R. Foot and X. G. He, Phys. Lett. B267, 509 (1991)

  • [16]

    B. C. Allanach, J. Davighi, and S. Melville, JHEP02, 082 (2019)

  • [17]

    S. L. Adler, Phys. Rev.177, 2426 (1969)

  • [18]

    J. S. Bell and R. Jackiw, Nuovo Cim. A60, 47 (1969)

  • [19]

    C. Bouchiat, J. Iliopoulos, and P. Meyer, Phys. Lett. B38, 519 (1972)

  • [20]

    J. Preskill, Ann. Phys.210, 323 (1991)

  • [21]

    D. Qiu and Y. Tang, JHEP2024, 167 (2024)

  • [22]

    C. Cai, H. J. He, J. Renet al., Phys. Rev. D106, 095003 (2022)

  • [23]

    A. Hook, Phys. Rev. D84, 055003 (2011)

  • [24]

    S. O. Kara, (2025), arXiv: 2508.18496

  • [25]

    A. Abadaet al. (FCC Collaboration), Eur. Phys. J. ST228, 261 (2019)

  • [26]

    M. Aicheleret al., (2012) Tech. Rep. CERN-2012-007 CERN

  • [27]

    M. Skrzypek and S. Jadach, Z. Phys. C49, 577 (1991)

  • [28]

    E. A. Kuraev and V. S. Fadin, Sov. J. Nucl. Phys.41, 466 (1985)

  • [29]

    K. Yokoya and P. Chen, (1992) Tech. Rep. SLAC-PUB-4935 SLAC

  • [30]

    A. Belyaev, N. D. Christensen, and A. Pukhov, Comput. Phys. Commun.184, 1729 (2013)

  • [31]

    J. Alwall, R. Frederix, S. Frixioneet al., JHEP07, 079 (2014)

  • [32]

    W. Kilian, T. Ohl, and J. Reuter, Eur. Phys. J. C71, 1742 (2011)

  • [33]

    t.~Electroweak (LEP, ALEPH, DELPHI, L3, OPAL, LEP Electroweak Working Group, SLD Electroweak Group and SLD Heavy Flavor Group), (2003), arXiv: hep-ex/0312023

  • [34]

    G. Cowan, K. Cranmer, E. Grosset al., Eur. Phys. J. C71, 1554 (2011)

  • [35]

    A. L. Read, J. Phys. G28, 2693 (2002)

  • [36]

    J. P. Leeset al. (BaBar Collaboration), Phys. Rev. Lett.113, 201801 (2014)

  • [37]

    E. Kouet al. (Belle-II Collaboration), Prog. Theor. Exp. Phys.2019, 123C01 (2019)

  • [38]

    G. Aadet al. (ATLAS Collaboration), JHEP10, 182 (2019), arXiv: 1903.06248

  • [39]

    A. M. Sirunyanet al. (CMS Collaboration), JHEP07, 208 (2021), arXiv: 2103.02708

  • [40]

    S. Schaelet al. (ALEPH, DELPHI, L3 and OPAL Collaborations), Phys. Lett. B565, 61 (2003), arXiv: hep-ex/0306031

  • [41]

    B. Abiet al. (Muon g-2 Collaboration), Phys. Rev. Lett.126, 141801 (2021), arXiv: 2104.03281

  • [42]

    J. Barreiro Guimarães da Costaet al. (CEPC Study Group), (2018), arXiv: 1811.10545

  • [43]

    T. Barklow, J. Brau, K. Fujiiet al., (2015), arXiv: 1506.07830

  • [44]

    J. de Blaset al., (2018), arXiv: 1812.02093

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