发表机构
School of Physics, Hefei University of Technology（合肥工业大学物理学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
我们提出一种利用反冲光子辅助定位位移双光子衰变顶点的方法，仅需一个转换光子，使效率线性提升，并在Belle II上扩展了轴子类粒子的探测参数空间。
AI 中文摘要
我们提出了一种反冲辅助策略，用于在$e^+e^-\to\gamma X$，$X\to\gamma\gamma$过程中定位位移双光子衰变的顶点，该方法仅需利用一个转换后的子光子。初态和反冲光子的动量定义了长寿命粒子（LLP）的飞行线，该飞行线与转换光子轨迹的最近点即为衰变顶点。这消除了对第二次转换的需求，使得与转换相关的效率随光子转换概率线性而非二次方地变化。对于Belle II上的亲光子轴子类粒子，现有的$408$ fb$^{-1}$数据集可以探测到先前未受约束的参数空间，接近$m_a \simeq 100$ MeV和$g_{a\gamma\gamma} \simeq 2 \times 10^{-4}$ GeV$^{-1}$。在$50$ ab$^{-1}$的数据量下，探测范围扩展到$m_a \simeq 310$ MeV和$g_{a\gamma\gamma}\simeq2\times10^{-5}$ GeV$^{-1}$。
英文摘要
We propose a recoil-assisted strategy for vertexing displaced diphoton decays in $e^+e^-\toγX$, $X\toγγ$, using only one converted daughter photon. The initial state and recoil-photon momentum define the LLP flight line, whose closest approach to the converted-photon trajectory locates the decay vertex. This removes the need for a second conversion, making the conversion-related efficiency scale linearly rather than quadratically with the photon-conversion probability. For photophilic axionlike particles at Belle II, the existing $408$ fb$^{-1}$ data set could probe previously unconstrained parameter space near $m_a \simeq 100$ MeV and $g_{aγγ} \simeq 2 \times 10^{-4}$ GeV$^{-1}$, improving leading bounds by almost an order of magnitude and testing the mass region below the $π^0$ mass, which the existing Belle II three-photon searches cannot access. With $50$ ab$^{-1}$, the reach extends to $m_a \simeq 310$ MeV and $g_{aγγ}\simeq2\times10^{-5}$ GeV$^{-1}$.
Comments6+12 pages, 4+4 figs
