White Paper on the Electron-Ion Collider in Preparation for the NSAC Long Range Plan

The scientific foundation for the Electron Ion Collider (EIC) has been built for over twodecades. Throughout, the EIC initiative was driven by maintaining U.S. leadership in both nuclear science and accelerator physics. These dual goals were clear from the outset, starting with the 2002 NSAC Long Range Plan [1] where “R&D over the next three years to address EIC design issues” was placed at high priority. Support from the community continued with the 2007 Long Range Plan [2] which recommended “the allocation of resources to develop accelerator and detector technology necessary to lay the foundation for a polarized Electron-Ion Collider” and culminated in the 2015 plan, where the EIC was identified as the “highest priority for new facility construction following the completion of FRIB” [3].

During this period the science case underpinning these recommendations was continually developed and documented by the growing EIC community, as illustrated in Fig.1.1. A series of workshops hosted by the Institute for Nuclear Theory laid the foundation for a White Paper titled “Understanding the glue that binds us all” [6]. The studies developed for this White Paper, combined with continued progress in accelerator R&D, served as input to a critical review in 2018 by the National Academy of Sciences (NAS). Their final report, An Assessment of the U.S. Based Electron-Ion Collider Science, concluded that “theEIC science is compelling, fundamental, and timely” [7].

The present White Paper serves as a compendium for these two decades of work. It will briefly summarize the flagship components of the EIC science case and discuss the current design of the collider and interaction regions. An update on the status of the project will be presented, including the ongoing design of the EPIC detector that will be built at the 6 o’clock interaction region and plans for a second, complementary detector to be constructed at the 8 o’clock region. Synergies with ongoing and future nuclear and particle physics programs will be discussed.