KSVZ轴子模型图谱中的小瞬子效应
Small-instanton effects in an atlas of KSVZ axion models
浏览论文内容
中文总结 AI 辅助
该研究分析KSVZ轴子模型中类矢量夸克的小瞬子对轴子势的贡献，修正了轴子质量与耦合的标准QCD关系，为轴子搜索提供新参数空间。
中文摘要 AI 辅助
我们利用朴素维度分析，研究了包含类矢量夸克（VQ）的一系列KSVZ模型中，小瞬子对轴子势的贡献。我们考虑了单VQ、多份相同VQ以及不同VQ组合的场景，每种场景都要求在双圈规范跑动下，规范耦合在普朗克能标前保持微扰性。这些场景对应的费米子零模内容各不相同，需要不同的质量插入组合以及标量-汤川收缩来实现饱和。增加VQ的份数会使瞬子尺寸积分由最小尺寸的瞬子主导，对应紫外（UV）截断附近的能标。由此产生的贡献会对紫外完备性敏感，且诱导的势可与普通QCD贡献相当甚至占主导。假设QCD势与小瞬子势对齐，我们确定了由此产生的轴子质量偏移及其对轴子-光子耦合的影响。当小瞬子诱导的 susceptibility 与QCD susceptibility 相当或更大时，固定衰变常数$f_a$下的物理轴子质量$m_a$会增强，而轴子-光子耦合$g_{a\beta\beta}$仍由$f_a$和反常比$E/N$控制。这修改了$m_a$、$f_a$和$g_{a\beta\beta}$之间的标准QCD关系，为轴子搜索开辟了$(m_a,g_{a\beta\beta})$平面的新区域。
英文摘要
We investigate small-instanton contributions to the axion potential across a range of KSVZ models containing vector-like quarks~(VQs), using naive dimensional analysis. We consider scenarios containing a single VQ, multiple identical copies, and sets of distinct VQs, requiring in each case that the gauge couplings remain perturbative up to the Planck scale under the two-loop gauge running. The associated fermion zero-mode content varies between these cases, requiring different combinations of mass insertions and scalar--Yukawa contractions for its saturation. Increasing the copies of VQs can render the instanton-size integral dominated by instantons of the smallest size, corresponding to the scale near the ultraviolet~(UV) cut-off. The resulting contribution then becomes sensitive to the UV completion and the induced potential can compete with, or dominate over, the ordinary QCD contribution. Assuming that the QCD and small-instanton potentials are aligned, we determine the resulting axion-mass shift and its consequences for the axion--photon coupling. When the small-instanton induced susceptibility becomes comparable to or larger than the QCD susceptibility, the physical axion mass of $m_a$ is enhanced at fixed decay constant~$f_a$, while the axion-photon of $g_{aγγ}$ coupling remains controlled by $f_a$ and the anomaly ratio of $E/N$. The standard QCD relation among $m_a$, $f_a$ and $g_{aγγ}$ is consequently modified, opening new regions of the $(m_a,g_{aγγ})$ plane for axion searches.
