MRI Consortium: Collaborative Research: Development of the Phase-I DarkLight Experiment at Jefferson Laboratory

粒子物理学是发现物质和能量的基本成分的科学，它涉及从最小到最大尺度的宇宙探索。二十世纪粒子物理学的一项显着成就是发展了标准模型，该模型很好地描述了诸如夸克和轻子等广泛的基本粒子以及它们之间的相互作用(力)。但标准模型是不完整的，我们知道在它之外还有重要的物理问题。证据是什么？例如，天文观测表明，标准模型的已知粒子只占宇宙总物质的六分之一。剩下的部分被称为“暗物质”，因为我们无法直接看到它。许多实验正在进行中或处于计划阶段，以寻找暗物质，它可能是一种粒子，也可能是许多粒子，也可能是完全不同的东西。这项核磁共振成像奖将允许来自暗光联盟机构的年轻物理学家在加速器科学、探测器和靶子的开发和利用、测量和分析方面进行出色的培训，并寻找超越标准模型的新物理的新证据。这项主要研究仪器奖授予麻省理工学院、汉普顿大学、亚利桑那州立大学和坦普尔大学的一个联盟，以在托马斯·杰斐逊国家实验室开发、建造和操作暗光实验的第一阶段。这个项目解决了粒子物理项目优先小组(称为P5)最近发布的报告的两个科学驱动力：暗物质和寻找新粒子和相互作用。暗光实验将利用杰斐逊实验室现有的能量回收直线加速器(ERL)的1兆瓦电子束，以100 MeV的速度入射到一个无窗的氢气靶上，以寻找电子和正电子对的证据，这些电子和正电子对可能是质量区域10到90 MeV的名为A‘的大质量暗光子的衰变产物。正如天体物理观测所表明的那样，这种A‘将轻子(如电子和正电子)耦合到暗物质，并可能解释与标准模型在Muon反常磁矩观测值(所谓的“g-2反常”)中可能存在的差异。黑暗之光有一个独特的功能，那就是寻找独家反应中的A‘in。暗光仪器的第一阶段实现将有三个科学目标：开展重要的加速器科学研究，涉及能量回收直线加速器光束与暗光气体目标和螺线管的相互作用；仔细测量标准模型背景过程；以及利用这一新的实验技术通过探测质量区域30至70 MeV/c2的电子对首次搜索A‘。

Particle Physics is the science of discovery of the fundamental constituents of matter and energy and is involved in the exploration of the Universe from the smallest to the largest scales. A remarkable achievement of Twentieth Century Particle Physics was the development of the Standard Model that describes impressively well a broad spectrum of fundamental particles such as quarks and leptons and the interactions (the forces) among them. But the Standard Model is incomplete and we know there is important physics that lies beyond it. What is the evidence? As an example, astronomical observations indicate that the known particles of the Standard Model make up only 1/6 of the total matter in the Universe. The remainder is called "Dark Matter" because we don't see it directly. A number of experiments are underway or in the planning stage to look for the Dark Matter, which might be one type of particle or possibly many or perhaps something else entirely. This MRI award will allow the excellent training of young physicists from the institutions in the DarkLight consortium in accelerator science, detector and target development and utilization, measurement and analysis, and search for new evidence of new physics beyond the Standard Model.This Major Research Instrumentation award is made to a consortium of MIT, Hampton University, Arizona State University and Temple University to develop, build and operate a first phase of the DarkLight experiment at Thomas Jefferson National Laboratory. This program addresses two of the science drivers of the recently released Report of the Particle Physics Project Prioritization Panel (called P5): Dark Matter and the Search for New Particles and Interactions. The DarkLight experiment will utilize the 1 Megawatt electron beam of the existing energy-recovering linac (ERL) at Jefferson Lab, incident at 100 MeV on a windowless hydrogen gas target, to search for evidence of electron and positron pairs which could be decay products of a massive Dark Photon called the A´ in the mass region 10 to 90 MeV. Such an A´ couples leptons (such as electrons and positrons) to dark matter, as suggested by astrophysical observations, and may explain a possible discrepancy with the Standard Model in the observed value of the anomalous magnetic moment of the muon (the so called "g-2 anomaly"). DarkLight has the unique feature of searching for the A´ in exclusive reactions. The phase-I realization of the DarkLight instrument will have three scientific goals: to carry out important accelerator science studies involving the interaction of the energy-recovering linac beam with the DarkLight gas target and solenoid; to carefully measure Standard Model background processes; and to carry out a first search for the A´ via detection of e+e- pairs in the mass region 30 to 70 MeV/c2 using this new experimental technique.