论文标题
增强对LHC处高粒度热量计的长寿命颗粒的敏感性
Enhancing Sensitivities to Long-lived Particles with High Granularity Calorimeters at the LHC
论文作者
论文摘要
在即将到来的大型强子对撞机的运行中，搜索长寿命颗粒（LLP）是一个令人兴奋的物理机会。在本文中，我们关注一种新的搜索策略，即在此类搜索中使用CMS检测器升级的一部分的高粒度量热仪（HGCAL）。特别是，我们证明了使用此升级的热量计的高粒度，这使我们可以在量热计中看到“淋浴轨道”，可以在识别信号和抑制背景方面发挥至关重要的作用。我们使用信号模型研究了HGCAL的潜在影响力，在该模型中，标准模型Higgs Boson腐烂成一对LLP，$ h \ to xx $。在仔细估算了标准模型QCD和误导的假轨道背景之后，我们为更保守的矢量玻色子融合触发器和一个新颖的基于流离失所的轨道触发器提供了预期的覆盖范围。我们的结果表明，Higgs衰减分支比率，Br $（h \ to xx）$的最佳覆盖范围在矢量 - 波森融合频道中约为$ \ Mathcal {o}（10^{ - 4}）$，带有lifetime $cτ_x\ sim \ sim 0.1 $ 0.1 $ - $ 1 $ - $ 1 $ - $ 1 $ $ 1 $ $ 1 $ $ 1 $。 $ \ MATHCAL {O}（10^{ - 5} \ text { - } 10^{ - 6}）$用于类似的寿命。另外，对于具有$Cτ_x\ sim 10^3 $米的LLP，基于HGCAL的搜索应能够在Gluon Gluon-Gluon Fusion（Vector Boson Fusion）中探测到几$ \ times 10^{ - 4} $（$ 10^{ - 2} $）的几个$ \ times 10^{ - 4} $（$ 10^{ - 2} $）。与这些先前的搜索相比，我们的新搜索显示了LLP参数空间互补区域的灵敏度增强。
The search for long-lived particles (LLP) is an exciting physics opportunity in the upcoming runs of the Large Hadron Collider. In this paper, we focus on a new search strategy of using the High Granularity Calorimeter (HGCAL), part of the upgrade of the CMS detector, in such searches. In particular, we demonstrate that the high granularity of the calorimeter with this upgrade, which allows us to see "shower tracks" in the calorimeter, can play a crucial role in identifying the signal and suppressing the background. We study the potential reach of the HGCAL using a signal model in which the Standard Model Higgs boson decays into a pair of LLPs, $h \to XX$. After carefully estimating the Standard Model QCD and the misreconstructed fake-track backgrounds, we give the projected reach for both a more conservative vector boson fusion trigger and a novel displaced-track-based trigger. Our results show that the best reach for the Higgs decay branching ratio, BR$(h \to XX)$, in the vector boson fusion channel is about $\mathcal{O}(10^{-4})$ with lifetime $cτ_X \sim 0.1$--$1$ meters, while for the gluon gluon fusion channel it is about $\mathcal{O}(10^{-5}\text{--}10^{-6})$ for similar lifetimes. Alternatively, for an LLP with $cτ_X \sim 10^3$ meters, the HGCAL based search should be able to probe BR$(h\to XX)$ down to a few $\times 10^{-4}$($10^{-2}$) in the gluon gluon fusion (vector boson fusion) channels, respectively. In comparison with these previous searches, our new search shows enhanced sensitivity in complementary regions of the LLP parameter space.
