Comprehensive constraints on ALP couplings from future $$e^+e^-$$ colliders, muon $$g-2$$, thermal dark matter and Higgs measurements

Abstract

In this article, we present projected 95% C.L. limits on axion-like particle (ALP) couplings from ALP production at a future

collider operating at

$$\sqrt{s} = 250~\text {GeV}$$ s = 250 GeV

with integrated luminosity

$$L = 0.5~\text {ab}^{-1}$$ L = 0.5 ab - 1

. We constrain the effective couplings

$$g_{\gamma \gamma }$$ g γ γ

,

$$g_{Z\gamma }$$ g Z γ

,

$$g_{ZZ}$$ g ZZ

, and

$$g_{WW}$$ g WW

over the ALP mass range

$$20~\text {GeV} \le m_a \le 100~\text {GeV}$$ 20 GeV ≤ m a ≤ 100 GeV

, finding projected bounds at the level of

$$\mathcal {O}(10^{-1})~\text {TeV}^{-1}$$ O ( 10 - 1 ) TeV - 1

for

$$g_{\gamma \gamma }/f_a$$ g γ γ / f a

. Given that the latest muon anomalous magnetic moment measurement (

$$\Delta a_\mu $$ Δ a μ

) shows no statistically significant deviation from the Standard Model prediction, we reinterpret the ALP contributions to

$$\Delta a_\mu $$ Δ a μ

as a stringent consistency requirement. We then derive the corresponding allowed regions for

$$g_{\gamma \gamma }$$ g γ γ

and the ALP–muon coupling

$$C_{\mu \mu }$$ C μ μ

, and apply them to a fermionic dark matter scenario in which the relic density depends on both the dark matter mass

$$m_\chi $$ m χ

and

$$m_a$$ m a

. The same parameter space is further constrained by Higgs signal strength measurements through

$$h \rightarrow \gamma \gamma $$ h → γ γ

and

$$h \rightarrow Z\gamma $$ h → Z γ

. A comparative analysis with existing experimental and theoretical bounds highlights the complementarity of

$$\Delta a_\mu $$ Δ a μ

, dark matter, and Higgs observables in restricting ALP couplings, demonstrating that even in the absence of a

$$\Delta a_\mu $$ Δ a μ

anomaly, these constraints provide essential guidance for viable ALP parameter space.