SI2-SSI: Collaborative Research: Jet Energy-Loss Tomography with a Statistically and Computationally Advanced Program Envelope (JETSCAPE)

大爆炸后的几微秒内，宇宙中充满了一种叫做夸克胶子等离子体的极热流体。随着宇宙的膨胀，这种等离子体冷却并凝聚成我们周围普通物质的积木：质子、中子和原子核。这种流体的液滴只存在于2万亿开尔文以上的温度，今天在布鲁克海文国家实验室和欧洲核子研究中心利用高能重离子的碰撞产生并研究了这种流体。研究夸克-胶子等离子体的一个关键方法是在碰撞中产生高能夸克和胶子，这些夸克和胶子与热等离子体相互作用，并以实验测量的粒子喷流的形式出现。这些喷嘴为研究等离子体的内部结构提供了强大的工具，类似于医学成像中的断层成像。然而，对射流测量的解释需要复杂的数值模拟和模拟，而理论计算与实验数据的比较需要先进的统计工具。JETSCAPE协作是一个由物理学家、计算机科学家和统计学家组成的跨学科团队，将开发一个全面的软件框架，提供一种系统的、严格的方法来应对这一挑战。培训计划、研讨会、暑期学校和MOOC将传播修改和维护这一框架所需的专业知识。JETSCAPE合作将开发一个可扩展和可移植的开源软件包，以取代各种现有代码。模块化集成软件框架将由相互作用的发生器组成，用于模拟(I)入射原子核的波函数，(Ii)热等离子体的粘性流体动力学演化，以及(Iii)等离子体中喷流的输运和修正。综合先进的统计分析工具将为非专家用户提供量化方法，通过与当前完整的实验数据进行比较，验证喷气改装的新理论描述。为了提高这项计算密集型任务的效率，合作伙伴将开发可培训的仿真器，通过在完整模型运行之间进行内插来准确预测实验观察值，并使用图形处理单元(GPU)等加速器进行流体动力学模拟和喷嘴改进。协作将用一个用户友好的信封创建这个框架，允许对其每个组成部分进行持续的修改、更新和改进。这项工作将作为其他领域的模板，涉及复杂的动态建模和与大型数据集的比较。这将开启高精度提取具有可量化不确定性的夸克-胶子等离子体内部结构的新时代。该项目推进了国家战略计算倡议(NSCI)的目标，该倡议旨在维持和加强美国在高性能计算(HPC)研究、开发和部署方面的科学、技术和经济领先地位。该项目得到了计算机与信息科学与工程局高级数字基础设施司以及数学和物理科学局物理司和数学科学司的支持。

Microseconds after the Big Bang, the universe was filled with an extremely hot fluid called the Quark-Gluon Plasma. As the universe expanded, this plasma cooled and condensed into the building blocks of ordinary matter around us: protons, neutrons, and atomic nuclei. Droplets of this fluid, which exists only at temperatures above 2 trillion Kelvin, are generated and studied in the laboratory today using collisions of high-energy heavy ions at Brookhaven National Laboratory and CERN. A key method to study the Quark-Gluon Plasma is the generation of high-energy quarks and gluons in the collision, which interact with the hot plasma and emerge as "jets" of particles that are measured by experiments. These jets provide powerful tools to study the internal structure of the plasma, analogous to tomography in medical imaging. However, interpretation of jet measurements requires sophisticated numerical modeling and simulation, and comparison of theory calculations with experimental data demands advanced statistical tools. The JETSCAPE Collaboration, an interdisciplinary team of physicists, computer scientists, and statisticians, will develop a comprehensive software framework that will provide a systematic, rigorous approach to meet this challenge. Training programs, workshops, summer schools and MOOCs, will disseminate the expertise needed to modify and maintain this framework.The JETSCAPE Collaboration will develop a scalable and portable open source software package to replace a variety of existing codes. The modular integrated software framework will consist of interacting generators to simulate (i) wave functions of the incoming nuclei, (ii) viscous fluid dynamical evolution of the hot plasma, and (iii) transport and modification of jets in the plasma. Integrated advanced statistical analysis tools will provide non-expert users with quantitative methods to validate novel theoretical descriptions of jet modification, by comparison with the complete set of current experimental data. To improve the efficiency of this computationally intensive task, the collaboration will develop trainable emulators that can accurately predict experimental observables by interpolation between full model runs, and employ accelerators such as Graphics Processing Units (GPUs) for both the fluid dynamical simulations and the modification of jets. The collaboration will create this framework with a user-friendly envelope that allows for continuous modifications, updates and improvements of each of its components. The effort will serve as a template for other fields that involve complex dynamical modeling and comparison with large data sets. It will open a new era for high-precision extraction of the internal structure of the Quark-Gluon Plasma with quantifiable uncertainties. This project advances the objectives of the National Strategic Computing Initiative (NSCI), an effort aimed at sustaining and enhancing the U.S. scientific, technological, and economic leadership position in High-Performance Computing (HPC) research, development, and deployment. This project is supported by the Division of Advanced Cyberinfrastructure in the Directorate for Computer & Information Science & Engineering and the Physics Division and the Division of Mathematical Sciences in the Directorate of Mathematical and Physical Sciences.