Over the past two decades, meson photo- and electroproduction data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even non-existent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state-of-the-art meson-beam facility needs to be constructed. The present letter summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.
Physics Opportunities with a Fixed-Target Program at the Electron-Ion Collider
Stony Brook University（石溪大学）；Michigan State University（密歇根州立大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）；University of California, Davis（加州大学戴维斯分校）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）
Snowmass 2021 White Paper: Electron Ion Collider for High Energy Physics
电子离子对撞机（Electron Ion Collider，EIC）是美国能源部计划在纽约长岛布鲁克海文国家实验室建造的一个粒子加速器设施。EIC将提供极化电子束与极化质子束和轻离子束碰撞的能力。EIC将是全球最大和最先进的新加速器设施之一，也是未来几十年美国计划建设的唯一一个新的大型加速器设施。EIC的多功能性，分辨率和强度将为解决粒子物理学中一些关键和基本的开放科学问题提供许多新的机会。本文从高能物理界的角度概述了EIC的科学案例。
