Since its inception, the hallmark of the STAR detector has been full acceptance mid-rapidity measurements with excellent particle identification capabilities.  Upgrades that are currently underway to maximize the physics output from Beam Energy Scan phase II will substantially enhance STAR’s already excellent capabilities.  These upgrades will enable STAR to continue its unique, ground-breaking mid-rapidity science program in the period following BES-II.

In this document, the STAR collaboration presents a science driven program for future polarized p+p, p+A A+A beam operations at RHIC. A suite of unique measurements that can only be made with a p+p , p +A, and Au+Au collider are discussed. The physics program described in this document complements the program discussed in the STAR forward upgrade proposal [[i]]. The program is designed to capitalize on STAR's existing resources, which include a proven multi-purpose detector, established calibration techniques and highly developed software infrastructure and are a natural extension of the current STAR physics program. The programs outlined here and in the forward upgrade proposal are an essential step towards the completion of the RHIC mission and will provide a natural transition to the highly anticipated electron-ion collider program.

The key physics opportunities envisioned address three broad areas of interest within the cold QCD community in the years following the BES-II. These programs will shed light on the dynamics of low and high x partons in cold nuclear matter (CNM) and how the fragmentation and hadronization of these partons is modified through interactions within the CNM and experiments to study the 2+1d spatial and momentum structure of protons and nuclei. These measurements will provide critical new insights into the QCD structure of nucleons and nuclei in the near term, as well as the high precision data that will be essential to enable rigorous universality tests when combined with future results from the EIC. In A+A collisions measurements with unprecedented precision using deep penetrating probes as leptons and photons will enable us to probe the whole evolution of the collision. In addition, significantly improved hypertriton lifetime measurements may have important implications on astrophysics. 

All projections and physics discussions are based on the following already planned data taking periods during the sPHENIX running periods in 2022 and 2023:

1.     2022: 20 weeks of Au+Au at √s = 200 GeV

2.     2023: 8 weeks transversely polarized p+p at √s = 200 GeV

3.     2023: 8 weeks each of transversely polarized p+Au and p+Al at √s = 200 GeV

In addition, a 20 week √s = 500 GeV polarized p+p run, split between transverse and longitudinal polarized running is proposed based on its merits for the overall physics program laid out in this document. This run could be scheduled in 2021, for which currently no dedicated physics program is assigned. It is especially noted none of the data taking periods proposed would result in any extra time delay to an eRHIC construction. It is also noted that this high impact and cost-effective physics program can be executed even in challenging financial times as all the needed detector capabilities are already existing in STAR.