Probing neutral triple gauge couplings via Z\gamma ({\ell }^{+}{\ell }^{-}\gamma ) production at e^{+}{e}^{-} colliders

Abstract

Neutral triple gauge couplings (nTGCs) are absent in the Standard Model (SM) and at the dimension-6 level in the Standard Model Effective Field Theory (SMEFT), arising first from dimension-8 operators. As such, they provide a unique window for probing new physics beyond the SM. These dimension-8 operators can be mapped to nTGC form factors whose structure is consistent with the spontaneously-broken electroweak gauge symmetry of the SM. In this work, we study the probes of nTGCs in the reaction e^{+}{e}^{-}\to Z\gamma with Z\to {\ell }^{+}{\ell }^{-}(\ell =e,\mu ) at an e^{+}{e}^{-} collider. We perform a detector-level simulation and analysis of this reaction at the Circular Electron Positron Collider (CEPC) with collision energy \sqrt{s}=240 GeV and an integrated luminosity of 20 ab⁻¹. We present the sensitivity limits on probing the new physics scales of dimension-8 nTGC operators via measurements of the corresponding nTGC form factors.

Graphical abstract

Keywords

anomalous gauge coupling / future colliders / Zγ / effective field theory / neutral triple gauge coupling

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Declarations

The authors declare that they have no competing interests and there are no conflicts.

Acknowledgements

The work of J.E. was supported in part by the United Kingdom STFC Grant ST/T000759/1. The work of H.J.H. and R.Q.X. was supported in part by the NSFC Grants 12175136 and 11835005. R.Q.X has also been supported by an International Postdoctoral Exchange Fellowship. We thank Gang Li, Yulei Zhang and Xuliang Zhu for discussions of the CEPC detector configuration.

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2024 Higher Education Press