A new insight on dark matter at the Large Hadron Collider

“暗物质是由什么构成的？”是我们这个时代粒子物理学中的一个大问题。难以捉摸的暗物质比普通物质丰富五倍，它塑造了我们宇宙的宇宙学演化。许多理论框架都认为暗物质是由新粒子组成的，这些新粒子只通过电弱相互作用与普通物质相互作用。欧洲核子研究中心的大型强子对撞机是目前唯一能够在高能质子-质子碰撞中产生这种粒子的机器：这是一个在可控、可复制的条件下发现并可能研究暗物质的独特机会。一种类似希格斯玻色子的粒子可能在暗物质的产生中起着至关重要的作用。它们的大汤川耦合使得第三代夸克与暗物质相关的候选事件的研究变得有趣。相关的底夸克或顶夸克产生低横向动量的情况在理论上是令人信服的，但尚未得到很好的研究。低横向动量底夸克（可能来自顶部衰变）很难识别，因为它们不一定在最终状态下产生强子射流。然而，它们仍然具有移位的衰变顶点的存在。我将通过多元分析来选择这样的事件，利用创新的低横向动量底夸克标记技术，在事件运动学信息的基础上。这些事件在过去从未被调查过：他们的研究将为探索暗物质带来有价值的新信息。

"What is dark matter made of?" is the big question of our times in particle physics. Five times more abundant than ordinary matter, the elusive dark matter has shaped the cosmological evolution of our universe.Many theoretical frameworks state that dark matter is made of new particles that interact only through electroweak interaction with ordinary matter. The Large Hadron Collider at CERN is the only existing machine that may be able to produce such particles in high-energy proton-proton collisions: this is a unique chance to discover, and possibly study, dark matter in controlled, reproducible conditions.A Higgs boson-like particle might play a crucial role as mediator of dark matter production. Their large Yukawa couplings make the study of candidate events where third generation quarks are produced in association with dark matter interesting. Scenarios where the associated bottom or top quarks are produced with low transverse momentum are theoretically compelling and not well studied yet.Low transverse momentum bottom quarks (possibly from top decay) are tricky to identify, as they do not necessarily yield a hadronic jet in the final state. However, they still feature the presence of a displaced decay vertex. I will select such events with a multivariate analysis exploiting innovative low transverse momentum bottom quark tagging techniques on top of information about the event kinematics. These events have never been investigated in the past: their study will bring valuable new information to the quest for dark matter search.