A new insight on dark matter at the Large Hadron Collider

“暗物质是由什么组成的？”是我们这个时代粒子物理学的一大问题。这种难以捉摸的暗物质的丰度是普通物质的五倍，它塑造了我们宇宙的宇宙学演化。许多理论框架声称，暗物质是由新粒子组成的，这些粒子只通过与普通物质的电弱相互作用而相互作用。欧洲核子研究中心的大型强子对撞机是现有的唯一一台可能能够在高能质子-质子碰撞中产生此类粒子的机器：这是在可控、可重复的条件下发现并可能研究暗物质的独特机会。类希格斯玻色子的粒子可能会作为暗物质产生的媒介发挥关键作用。它们的大汤川耦合使研究与暗物质相关的第三代夸克产生的候选事件变得有趣。低横向动量的底夸克或顶夸克的产生在理论上是引人注目的，但目前还没有得到很好的研究。低横向动量的底夸克(可能来自顶部衰变)很难识别，因为它们不一定会在终态产生强子喷流。但是，它们仍然具有置换的衰退顶点的存在。我将在事件运动学信息的基础上，利用创新的低横向动量底夸克标记技术，通过多变量分析来选择这样的事件。这些事件过去从未被研究过：他们的研究将为寻找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.