论文标题
在LHC上寻找黑暗辐射
Searching for dark radiation at the LHC
论文作者
论文摘要
在这项工作中，我们探讨了在LHC和早期宇宙宇宙学上对长寿命颗粒（LLP）的搜索之间的有趣联系。我们通过弱尺度LLP的衰变研究了早期宇宙中超相关颗粒（即暗辐射）的非热产生，并表明宇宙学上有趣的范围$δn_\ text {eff} \ sim 0.01-0.1 $对应于mmmmmm to cm范围的LLP衰减长度。这些衰减长度位于LHC处提示和流离失所的签名之间的边界，可以通过组合两者的搜索来全面探索。为了说明这一点，我们考虑了一个场景，其中LLP腐烂了带电的Lepton和一个（几乎）无质量的无形粒子。通过重新解释搜索迅速衰减的Sleptons和Atlas和CMS的流离失所的瘦素，我们可以直接将LHC排除与宇宙学可观察物进行比较。我们发现，当前LHC搜索已经排除了$Δn_\ text {eff} = 0.06 $的CMB-S4目标值，甚至可以在Electroweak量表上探测LLP质量的较小值。
In this work we explore the intriguing connections between searches for long-lived particles (LLPs) at the LHC and early universe cosmology. We study the non-thermal production of ultra-relativistic particles (i.e. dark radiation) in the early universe via the decay of weak-scale LLPs and show that the cosmologically interesting range $ΔN_\text{eff} \sim 0.01-0.1$ corresponds to LLP decay lengths in the mm to cm range. These decay lengths lie at the boundary between prompt and displaced signatures at the LHC and can be comprehensively explored by combining searches for both. To illustrate this point, we consider a scenario where the LLP decays into a charged lepton and a (nearly) massless invisible particle. By reinterpreting searches for promptly decaying sleptons and for displaced leptons at both ATLAS and CMS we can then directly compare LHC exclusions with cosmological observables. We find that the CMB-S4 target value of $ΔN_\text{eff}=0.06$ is already excluded by current LHC searches and even smaller values can be probed for LLP masses at the electroweak scale.
