Muon collider probes of the gluonic quartic gauge couplings

TL;DR

This paper assesses the sensitivity of future high-energy muon colliders to dimension-8 gluonic quartic gauge couplings (gQGCs) within the SMEFT framework, focusing on the μ⁺μ⁻ → ggγ channel. It presents eight gQGC operators with distinct Lorentz structures, analyzes their kinematic signatures and a cut-based signal extraction strategy using realistic detector simulations, and derives projected constraints on the corresponding Wilson coefficients and new-physics scales. The results show that MuCs can probe multi-TeV scales, with hypercharge-type operators (i=4–7) typically offering the strongest reach, significantly beyond current LHC bounds. The work also connects collider sensitivities to fundamental positivity bounds and to ultraviolet completions such as Born–Infeld-like theories, highlighting MuCs as a powerful platform to test purely dimension-8 gluonic interactions and consistency conditions of the EFT framework. Overall, the study demonstrates that μ⁺μ⁻ → ggγ provides a clean, highly sensitive probe of gluonic dimension-8 new physics at multi-TeV MuCs, with potential to test positivity and UV scenarios in the gluonic sector.

Abstract

We investigate the dimension-8 gluonic quartic gauge couplings (gQGCs) at future high-energy muon colliders through the process $μ^{+}μ^{-}\!\to ggγ$. Using detailed event simulation and optimized kinematic selections, we derive projected sensitivities to the Wilson coefficients and their associated new-physics scales, showing that muon colliders can probe deep into the multi-TeV regime and significantly surpass current LHC bounds. We further present the positivity bounds on those Wilson coefficients, as theoretical constraints from the fundamental principles of quantum field theory. Our results establish $μ^{+}μ^{-}\!\to ggγ$ as one of the most sensitive probes of dimension-8 new physics at future muon colliders.

Figures (7)

• Figure 1: Representative Feynman diagrams for (a) $\mu^+\mu^-\!\to gg\gamma$ induced by gQGC operators, and (b) the dominant SM background $\mu^+\mu^-\!\to q \bar{q} \gamma$.
• Figure 2: Normalized transverse momentum of leading jet $p_T^{j}$ distributions for signals generated by different operators and SM background at 3, 10 and 30 TeV MuC.
• Figure 3: The same configuration as in Fig. \ref{['jpt']}, but for photon energy $E_{\gamma}$.
• Figure 4: The same configuration as in Fig. \ref{['jpt']}, but for pseudorapidity of photon $\eta_{\gamma}$.
• Figure 5: The same configuration as in Fig. \ref{['jpt']}, but for pseudorapidity of leading jet $\eta_{j_{max}}$.