宇宙射线背景在Atomki异常中的重要性
On the importance of cosmic-ray background in the Atomki anomaly
- INFN（意大利国家核物理研究所）
- University of Pavia（帕维亚大学）
- University of Rome La Sapienza（罗马第一大学）
- University of Pisa（比萨大学）
- Paul Scherrer Institut PSI（保罗谢尔研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过Geant4模拟表明，宇宙射线缪子背景在Atomki五臂和六臂谱仪中可产生与17 MeV玻色子证据相似的开角过剩，强调宇宙射线处理对此类异常搜索的关键重要性。
AI中文摘要：
我们报告了基于Geant4的宇宙射线缪子背景模拟，这些模拟在再现德布勒森Atomki小组操作的五臂和六臂e+e-对谱仪几何结构的模型中进行。两种装置均实现了完整的探测器几何结构，包括位置灵敏探测器和塑料闪烁体。在两种配置中，产生两臂符合的宇宙缪子在开角分布中产生了统计显著的过剩，其位置由探测器臂的离散方位角排列和塑料闪烁体尺寸决定：在六臂谱仪中，当闪烁体能和选择在8Be跃迁窗口（16-20 MeV）内时，在140度附近出现峰值，且对于能量不对称的电子对受到抑制，而在4He窗口（18-22 MeV）中则在120度附近出现明显峰值，在相应的背景能量区域没有可比的增强。这些角度、不对称性依赖性和背景特征表现出与Atomki小组报告的作为17 MeV玻色子证据的行为相似。对于五臂装置，在8Be能量下也重现了140度过剩，将内部对转换事件和宇宙符合归一化到典型的Atomki运行条件，得到信号窗口内宇宙与IPC之比大于1，表明宇宙背景在感兴趣的能量和角度下对事件率有主要贡献。虽然这些结果并未解决Atomki过剩起源的问题，但它们突显了在此类测量中进行稳健宇宙射线处理的关键重要性，并呼吁对支持在信号区域周围开角与总能和分布中搜索异常的束流关闭研究进行详细描述。
英文摘要：
We report Geant4-based simulations of cosmic-ray muon backgrounds in models reproducing the geometries of the five-arm and six-arm e+e- pair spectrometers operated by the Atomki group at Debrecen. Full detector geometries are implemented for both setups, including position-sensitive detectors and plastic scintillators. In both configurations, cosmic muons generating two-arm coincidences produce statistically significant excesses in the opening-angle distribution whose positions are determined by the discrete azimuthal arrangement of detector arms and the plastic scintillators dimensions: in the six-arm spectrometer a peak appears near 140 degrees when the scintillator energy sum is selected in the 8Be transition window (16-20 MeV) and is suppressed for energy-asymmetric pairs, while a distinct peak near 120 degrees emerges in the 4He window (18-22 MeV), with no comparable enhancement in the respective background energy region. These angles, asymmetry dependences, and background characteristics show behaviours similar to those reported by the Atomki group as evidence for a 17 MeV boson. For the five-arm setup, a 140-degree excess is also reproduced at 8Be energies, and normalizing internal pair conversion events and cosmic coincidences to typical Atomki running conditions yields a cosmic-to-IPC ratio above unity in the signal window, indicating that the cosmic background is a leading contribution to the event rate at the energies and angles of interest. While they do not settle the question of the origin of the Atomki excesses, these results highlight the critical importance of a robust cosmic-ray treatment in this type of measurements, and call for a detailed description of the beam-off studies supporting the search for anomalies in the opening-angle vs. energy-sum distribution around the signal region.
