通过γγ衰变道直接测量介质中η′质量谱
Direct measurement of the in-medium $η^{\prime}$ mass spectrum through the $γγ$ decay channel
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中文总结 AI 辅助
该研究通过γγ衰变道直接测量η′(958)介子在核介质中的不变质量，发现低动量事件的质量峰低尾部增强，统计显著性达3.7σ以上，测得质量减少量为57.5⁺⁵.⁷₋₂₇.⁸ MeV/c²，提供了η′介质中谱修正的首个直接测量证据。
中文摘要 AI 辅助
我们通过η′(958)→γγ衰变道测量了η′(958)介子的不变质量，以探究η′在核介质中可能的性质变化。通过拟合真实谱函数对测量得到的不变质量谱进行分析，在低动量（P_γγ < 1 GeV/c）事件的η′质量峰低尾部观测到增强现象。采用三种统计方法评估该增强的显著性，所有方法均给出高于3.7σ的统计显著性。谱拟合表明质量减少量为57.5⁺⁵.⁷₋₂₇.⁸ MeV/c²。我们的结果提供了通过直接测量η′不变质量获得的η′介子在介质中谱修正的首个证据。
英文摘要
We measured the invariant mass of the $η^{\prime}(958)$ meson through the $η^{\prime}\toγγ$ decay channel to search for possible character change of $η^{\prime}$ in a nuclear medium. The measured invariant-mass spectra were analyzed by fitting realistic spectral functions. An enhancement was observed in the lower tail of the $η^{\prime}$ mass peak for low-momentum ($P_{γγ} < 1$~$\mathrm{GeV/c}$) events. Three statistical methods were applied to assess the significance of the enhancement. All methods yield a statistical significance above 3.7$σ$. The spectral fitting indicates a mass reduction of $57.5^{+~5.7}_{-27.8}$~$\mathrm{MeV/c}^{2}$. Our result provides the first evidence for an in-medium spectral modification of the $η^{\prime}$ meson obtained through a direct measurement of its invariant mass.
