费米子门户到矢量暗物质的新型多轻子特征
Novel Multilepton Signatures from the Fermionic Portal to Vector Dark Matter
AI总结：
研究费米子门户到矢量暗物质产生的新型多轻子特征，开发基于拓扑的重建方法，利用信号共振结构，模拟信号与背景，确定六μ子通道为有力目标，可扩展对矢量类μ子质量的探测范围，如HL - LHC可达约1.9 TeV。
AI中文摘要：
我们对一种新型多轻子特征进行了对撞机研究，该特征源于重矢量类轻子的对产生，随后通过暗区进行级联衰变。在费米子门户到矢量暗物质的μ子实现中，此过程可导致具有四个、六个、八个或十个可见μ子的末态，具体取决于暗区光谱和分支模式。我们将六μ子通道确定为最有力的目标：它在参数空间的广泛区域内仍然可观，比更高多重性通道的速率抑制更小，比四μ子末态更干净且更易于重建。信号源于矢量类μ子的Drell - Yan对产生，$pp\to\mu'^{+}\mu'^{-}$，随后通过暗矢量$V'$和暗标量$H_D$衰变。六μ子末态接收来自对称衰变拓扑（其中每个$\mu'$产生三个可见μ子）和非对称拓扑（其中一个链产生一个μ子而另一个产生五个μ子）的贡献。矢量类轻子对产生的六轻子特征此前在大型强子对撞机上尚未被探索。因此，我们开发了一种基于拓扑的重建方法，利用信号中重复的双μ子、三μ子和五μ子共振结构。我们在探测器层面模拟了信号和标准模型背景，包括对罕见重味μ子的专门处理。经过六μ子选择和拓扑重建后的背景可以忽略不计。现有的Run - 2多轻子搜索已经限制了部分低质量参数空间，但它们没有利用信号的重复共振结构。专门的六μ子搜索可以大幅扩展探测范围。在高亮度大型强子对撞机上，对于有利的光谱，所提出的分析可以探测到高达约1.9 TeV的矢量类μ子质量。
英文摘要：
We perform a collider study of a novel multilepton signature arising from pair production of heavy vector-like leptons followed by cascade decays through a dark sector. In the muonic realisation of the Fermionic Portal to Vector Dark Matter, this process can lead to final states with four, six, eight, or ten visible muons, depending on the dark-sector spectrum and branching pattern. We identify the six-muon channel as the most powerful target: it remains sizeable over a broad region of parameter space, while being less rate-suppressed than the higher-multiplicity channels and much cleaner and more reconstructable than the four-muon final state. The signal arises from Drell--Yan pair production of vector-like muons, $pp\toμ'^{+}μ'^{-}$, followed by decays through the dark vector $V'$ and the dark scalar $H_D$. The six-muon final state receives contributions from symmetric decay topologies in which each $μ'$ yields three visible muons, and from the asymmetric topology in which one chain yields one muon and the other yields five. The six-lepton signature from vector-like-lepton pair production has not previously been explored at the LHC. We therefore develop a topology-based reconstruction which exploits the repeated dimuon, trimuon, and five-muon resonance structure of the signal. We simulate signal and Standard Model backgrounds at detector level, including a dedicated treatment of rare heavy-flavour muons. The resulting background after the six-muon selection and topology reconstruction is negligible. Existing Run-2 multilepton searches already constrain part of the low-mass parameter space, but they do not exploit the repeated resonance structure of the signal. A dedicated six-muon search can substantially extend the reach. At the HL-LHC, the proposed analysis can probe vector-like muon masses up to about $1.9$ TeV for favourable spectra.
