在CMS上通过数据停放与侦察技术探测矢量玻色子融合过程中的轻轴子类粒子
Probing light axion-like particles in vector boson fusion at CMS with data parking and scouting
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中文总结 AI 辅助
针对LHC上轻ALP探测的软事件与合并光子难题，CMS结合数据停放与径迹重建，在Run 3和HL-LHC上首次覆盖未探测量区，灵敏度提升约一个数量级。
中文摘要 AI 辅助
质量在10 MeV至10 GeV之间且耦合强度适中偏小的轴子类粒子（ALPs）处于实验盲区。它们衰变过快，无法被强度前沿实验捕捉；同时耦合过弱、质量过轻，常规对撞机搜索也难以触及。大型强子对撞机（LHC）通过矢量玻色子融合（VBF）过程以可观速率产生这类粒子，这是电磁耦合ALPs的主要产生模式，但两大障碍使该信号难以探测。事件能量较低，触发阈值会丢弃大部分事件；同时洛伦兹助推将两个衰变光子合并为单一量能器沉积。我们证明紧凑缪子螺线管（CMS）实验可通过结合其数据采集策略与基于径迹器的合并光子对重建来克服这两大障碍。在Run 3（312 fb$^{-1}$）中针对VBF喷注拓扑的数据停放，以及高亮度LHC（HL-LHC，3 ab$^{-1}$）上的触发级数据侦察，消除了对光子阈值的需求。在硅径迹器中转换为电子-正电子对的光子可分辨合并光子对，因为径迹器测量其方向远比量能器粒度精细。从转换径迹重建ALP衰变顶点可排除瞬发本底，但无法排除长寿命的$K_L\to\gamma\gamma$过程。在Run 3中，由于记录完整事件，合并双光子不变质量将$K_L$限制在其自身质量附近的窄窗口内。在侦察流中，仅保留触发级信息，双光子$p_T$、转换径迹及事件中的强子活动承担此角色。我们预计已记录的停放Run 3数据可达到$(m_a, g_{a\gamma\gamma})$参数平面中尚无任何测量探索的区域。HL-LHC上的Level-1触发数据侦察将该覆盖范围在耦合和质量两个维度上扩展约一个数量级。
英文摘要
Axion-like particles (ALPs) with masses between 10 MeV and 10 GeV and moderately small couplings sit in an experimental blind spot. They decay too fast for intensity-frontier experiments and are too feebly coupled and too light for conventional collider searches. The LHC produces them at substantial rates through vector boson fusion (VBF), the dominant production mode for electromagnetically coupled ALPs, but two obstacles keep this signal out of reach. The events are soft, so trigger thresholds discard most of them, and the Lorentz boost merges the two decay photons into a single calorimeter deposit. We show that the Compact Muon Solenoid (CMS) experiment can overcome both by combining its data-acquisition strategies with the tracker-based reconstruction of merged photon pairs. Data parking on the VBF jet topology in Run 3 (312 fb$^{-1}$) and trigger-level data scouting at the High-Luminosity LHC (HL-LHC, 3 ab$^{-1}$) remove the need for a threshold on the photons. Photons that convert to electron-positron pairs in the silicon tracker resolve the merged pair, since the tracker measures their direction far more finely than the calorimeter granularity. Reconstructing the ALP decay vertex from the conversion tracks removes the prompt backgrounds but not the long-lived $K_L\toγγ$. In Run 3, where the full event is recorded, the merged diphoton invariant mass confines the $K_L$ to a narrow window around its own mass. In the scouting stream, where only trigger-level information survives, the diphoton $p_T$, the conversion tracks, and the hadronic activity in the event take over this role. We project that the parked Run 3 data, already recorded, reach a region of the $(m_a, g_{aγγ})$ plane that no measurement has probed. Level-1 trigger data scouting at the HL-LHC extends that reach by roughly an order of magnitude in both coupling and mass.
发表机构
- Carnegie Mellon University（卡内基梅隆大学）
- University of Pennsylvania（宾夕法尼亚大学）
- Instituto Galego de Física de Altas Enerxías, Universidade de Santiago de Compostela（圣地亚哥-德孔波斯特拉大学加利西亚高能物理研究所）
- Universität Heidelberg（海德堡大学）
机构由 AI 辅助整理，请以论文原文为准。
