The much-anticipated 2023 Particle Physics Project Prioritization Panel (P5) Report presents a vision for US particle physics that builds on recent investments and successes, while opening pathways to innovation and discovery. These have the potential to open a new era of insight and discovery in the fundamental physics of the smallest constituents of our universe, as well as how their properties imprint on its large-scale structure.
The P5 report outlines a 10-year strategic plan in the context of a 20-year vision addressing where the field of particle physics should go and how to get there in a budget-conscious plan. The report builds on the community input of the Snowmass community study process (2022 newsletter), as well as P5 town hall events that included a strong accelerator component. Five specific science drivers were identified, most of which rely on unique beams, leveraging recent advances in particle accelerators, ranging from new records in RadioFrequency (RF) gradient to novel high field magnets and beyond. Achieving physics goals beyond this decade will require transformational advances in the capabilities of accelerators.
This motivates a combination of general and collider-targeted R&D, along with projects and investment in the Fermilab complex. Expansion of the General Accelerator R&D program within HEP is envisioned to drive the innovation required to meet the increasing demands on accelerator capacity, performance, efficiency and cost. At the same time, a program of targeted collider R&D is envisioned to translate advancements in detector and accelerator technology into plans for collider facilities. It will develop plans for a near-term Higgs factory and address needs for a collider at 10 TeV per parton (10 TeV pCM) for particle physics studies ranging from precision Higgs self-interaction, to new spinless particles, to testing of WIMP theories and others. Experiments and test facilities should be used to develop general technology and targeted methods to reduce cost and risk, guided by collider R&D and simulations. Decisions on a Higgs factory project, major test and demonstrator facilities, and Fermilab complex plans are envisioned via a panel this decade. If funding is available, broad accelerator science and technology development at both DOE and NSF, including partnerships, also has great potential.
The highest P5 priority is to complete projects and support operations of ongoing experiments and research to enable maximum science. Accelerator projects include the High Luminosity Upgrade of the Large Hadron Collider, and the PIP-II project supporting the first phase of the DUNE experiment. Enabled by advances in superconducting magnets, RF structures, and high intensity beam dynamics and control among other accelerator fields, these projects are positioned to enable the next generation of collider and neutrino physics respectively.
New initiatives are poised to transform our understanding. A second phase of DUNE, including ACE-MIRT, an enhanced 2.1 MW accelerator with very high beam intensity, will be the definitive long-baseline neutrino oscillation experiment of its kind.
An offshore e+e- Higgs factory at a fraction of a TeV, in collaboration with international partners, will open up the secrets of the Higgs boson and its interactions; FCC-ee and ILC meet the needs. It is important for the US to actively engage in feasibility and design studies, and to develop the required technologies. Once a specific project is deemed feasible and well-defined (envisioned in the five-year time frame) we should aim for a contribution commensurate with our involvement in the LHC. To facilitate this, the U.S. Department of Energy (DOE) is starting a nationally coordinated U.S. Higgs Factory Coordination Consortium for Accelerators (HFCC-A) to provide strategic direction and leadership for the U.S. community to engage, and a US-CERN joint statement of intent has been issued on FCC collaboration.
Work is required this decade to develop the resources essential to the future of the field, including vigorous R&D toward a cost-effective 10 TeV pCM collider that could be based on proton, muon or possible wakefield technologies. A 10 TeV collider places stringent demands on accelerator performance, efficiency and precision, and there is not a mature technology. While this collider would be beyond the next decade, its timely realization motivates development of technologies for each option under general R&D as well as targeted collider R&D to guide development and evaluation of options for US siting of such a machine. Readiness to build major test and demonstrator facilities within the next 10 years is a goal towards proving technical elements and preparing for a future project.
In parallel, plans for the future of the Fermilab complex should be developed supporting neutrino and flavor physics, as well as 10 TeV collider options consistent with the long-term vision of the report.
It is an exciting time in accelerator science, with major facilities nearing completion while advances in R&D continue to extend the possibilities of particle physics (and of broad applications) including the possibility of discovery at the 10 TeV pCM scale. Realizing this will require a strong workforce seeded by university and training programs and by R&D, and by a strong community fostered by work to broaden engagement and steward ethical conduct in the field. Global investment in accelerator-related technologies has increased dramatically over the last decade reflecting the broad importance of the field to endeavors ranging from scientific and technical capabilities to health. The community, in partnership with DOE-HEP as well as NSF and other offices and agencies, has an opportunity to lead the accelerator development that will open these frontiers while delivering broader benefits across science and society.
The article was first published in the 2024 Newsletter of the American Physical Society’s Division of Physics of Beams and can be read here.
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