Title: High Energy Physics Network Requirements Review (Final Report, July-October 2020)

Throughout 2020, ESnet and the Office of High Energy Physics (HEP) of the DOE SC organized an ESnet requirements review of HEP-supported activities. Preparation for this event included identification of key stakeholders: program and facility management, research groups, technology providers, and a number of external observers. These individuals were asked to prepare formal case study documents about their relationship to the HEP program to build a complete understanding of the current, near-term, and long-term status, expectations, and processes that will support the science going forward. A series of pre-planning meetings better prepared case study authors for this task, along with guidance on how the review would proceed in a virtual fashion. The HEP program’s mission is to understand how the universe works at its most fundamental level by discovering the elementary constituents of matter and energy, probing the interactions between them, and exploring the basic nature of space and time. This research and development (R&D) inspires young minds, trains an expert workforce, and drives innovation that improves the nation’s health, wealth, and security. The scientific objectives and priorities for the field recommended by the High Energy Physics Advisory Panel (HEPAP) are detailed in its recent long-range strategic plan, developed by the Particle Physics Project Prioritization Panel (P5)1. HEP research is inspired by some of the most fundamental questions about our universe. What is it made of? What forces govern it? How did it evolve to the way it is today? Finding these answers requires the combined efforts of some of the largest scientific collaborations in the world, using large arrays of the most sensitive detectors in the world, at some of the largest and most complex scientific machines in the world. HEP supports US researchers who play leading roles in these international efforts and world-leading facilities at our national laboratories that make this science possible. HEP also develops new accelerator, detector, and computational tools to open new doors to discovery science, and through the Accelerator Stewardship program, works to make transformational accelerator technology widely available to science and industry.