We study hidden-sector particles at past (CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration and NuCal), present (NA62, SeaQuest, and DarkQuest), and future (LongQuest) experiments at the high-energy intensity frontier. We focus on exploring the minimal vector portal and the next-to-minimal models in which the productions and decays are decoupled. These next-to-minimal models have mostly been devised to explain experimental anomalies while avoiding existing constraints. We demonstrate that proton fixed-target experiments provide one of the most powerful probes for the MeV to few GeV mass range of these models, using inelastic dark matter (iDM) as an example. We consider an iDM model with a small mass splitting that yields the observed dark matter relic abundance, and a scenario with a sizable mass splitting that can also explain the muon $g-2$ anomaly. We set strong limits based on the CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration and NuCal experiments, which come close to excluding iDM as a full-abundance thermal dark matter candidate in the MeV to GeV mass range. We also make projections based on NA62, SeaQuest, and DarkQuest and update the constraints of the minimal dark photon parameter space. We find that NuCal sets the only existing constraint in $\epsilon \sim {10}^{-8}–{10}^{-4}$ regime, reaching $\sim 800\mathrm{MeV}$ in dark photon mass due to the resonant enhancement of proton bremsstrahlung production. These studies also motivate LongQuest, a three-stage retooling of the SeaQuest experiment with short ($\lesssim 5\mathrm{m}$), medium ($\sim 5\mathrm{m}$), and long ($\gtrsim 35\mathrm{m}$) baseline tracking stations and detectors as a multipurpose machine to explore new physics.

中文翻译：

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暗光子和Muong-2激发的高能强度边界的非弹性暗物质模型

我们研究了过去（CERN-汉堡-阿姆斯特丹-罗马-莫斯科合作和NuCal），现在（NA62，SeaQuest和DarkQuest）以及将来（LongQuest）在高能强度边界的实验中的隐藏扇区粒子。我们专注于探索最小矢量门户和次最小模型，其中产量和衰变是分离的。这些次要的模型主要用于解释实验异常，同时避免现有的限制。我们证明了质子固定目标实验以非弹性暗物质（iDM）为例，为这些模型的少数GeV质量范围提供了MeV的最强大的探针之一。我们考虑一个iDM模型，该模型具有较小的质量分裂，可产生观察到的暗物质遗迹丰度；以及一个具有较大质量分裂的场景，该场景也可以解释μon$G-\mathrm{2个}$异常。我们基于欧洲核子研究组织-汉堡-阿姆斯特丹-罗马-莫斯科合作和NuCal实验设定了严格的极限，接近将iDM排除为MeV至GeV质量范围内的全热暗物质候选者。我们还基于NA62，SeaQuest和DarkQuest进行投影，并更新最小暗光子参数空间的约束。我们发现NuCal在$\epsilon 〜{10}^{-8}–{10}^{-4}$ 政权，达到 $〜800\mathrm{电动汽车}$由于质子致辐射产生的共振增强，在暗光子质量中产生了光子。这些研究还激发了LongQuest，这是SeaQuest实验的三个阶段的重新设计，$\lesssim 5\mathrm{米}$）， 中等的 （$〜5\mathrm{米}$）和长（$\gtrsim 35\mathrm{米}$）基线跟踪站和检测器，作为探索新物理的多功能机器。