AI 中文总结
研究耦合粲夸克的GeV尺度QCD轴子，采用重介子手征微扰理论，分析多个相关过程，未出现致命约束，最强限制来自σ介导的B_s - B_s混合，轴子 - 介子混合开启可检验稀有衰变但速率略低。
AI 中文摘要
具有仅粲夸克佩切伊 - 奎因耦合的QCD轴子规避了χPT中轻夸克模型的同位旋破缺问题。由于粲质量大于 QCD 标度，我们采用重介子手征微扰理论（HMChPT）来约束这个GeV尺度的轴子，包括其 CP 偶数径向伙伴σ和轴子 a。在 HMChPT 中，σ以 O(1)耦合进入领头阶，而 a 仅在 O(1/m_c)耦合并通过轴子 - 介子混合体现，混合角约为 f_π/f_a ∼ 0.04。我们分析了 D 介子质量、D - D*分裂、粲偶素、D - D 散射、B_s 混合、稀有 D 衰变以及 K^+→π^+a、B→K a 等过程。与χPT同位旋问题不同，未出现致命的 HMChPT 约束。最强的限制来自σ介导的 B_s - B_s 混合；轴子 - 介子混合开启了可检验的稀有衰变，尽管速率略低于当前灵敏度。
英文摘要
The QCD axion with charm-only Peccei-Quinn coupling evades the isospin-violation problem of light-quark models in $χ$PT. Since $m_c>Λ_{\rm QCD}$, we employ heavy meson chiral perturbation theory (HMChPT) to constrain this GeV-scale axion, including its CP-even radial partner $σ$ and the axion $a$. In HMChPT, $σ$ enters at leading order with $O(1)$ coupling, while $a$ couples only at $O(1/m_c)$ and manifests via axion-pion mixing with $θ_{aπ}\simeq f_π/f_a\sim0.04$. We analyze $D$-meson masses, $D$-$D^*$ splitting, charmonium, $D$-$D$ scattering, $B_s$ mixing, rare $D$ decays, and the channels $K^+\toπ^+a$, $B\to K a$. No fatal HMChPT constraint emerges, unlike the $χ$PT isospin issue. The strongest bound is from $σ$-mediated $B_s$-$\bar B_s$ mixing; axion-pion mixing opens testable rare decays, though rates are slightly below current sensitivity.
Comments43 pages, 7 tables, comments are welcome
