Scientists from across the country and key international partners making up the Particle Physics Project Prioritization Panel (P5) have recently sent their recommendations to U.S. funding agencies for what research projects in particle physics should be pursued in the next decade. On Dec. 8, 2023, the High Energy Physics Advisory Panel (HEPAP), a permanent advisory committee to the United States Department of Energy (DOE) and the National Science Foundation (NSF), approved this P5 report.
Roughly every 10 years, funding agencies, including the DOE and the NSF, convene a panel to decide what priorities to fund and focus on for the next decade. It was a year-long process that first gathered information from the scientific community and then decided which particle physics projects to recommend to HEPAP.
The P5 report consisted of a panel of about 30 scientists worldwide, including University of New Mexico Assistant Professor Francis-Yan Cyr-Racine.
“This was a difficult exercise. We had to make hard choices. We took all this input from the community and hopefully processed it into a coherent report. It was a time-consuming process, and it took a lot of work to make sure that we convey the right message,” explained Cyr-Racine.
Starting in February 2023, the panel participated in in-person town halls where the panel traveled to four different national labs throughout the country. The panel first listened to the community about other projects and science cases to determine what projects to pursue.
The report highlights six research directions: understanding neutrinos, revealing the nature of the Higgs boson, determining what dark matter is, understanding what drives the evolution of the cosmos, searching for new particles outside our present paradigm, and seeking quantum imprints of new phenomena.
The P5 report contains a portfolio of large, medium, and small projects and a budget for each project. While having to determine which science to pursue, Cyr-Racine explained that they had to consider the cost of all of these projects. Not only did the scientists have to weigh the science opportunities, but they also had budget guidelines to consider to determine the amount of funds the panel could spend on all these projects.
“Of course, it's hard to please everyone. But I think we came up with a well-balanced portfolio of research projects that will move particle physics and cosmology forward in the next decade,” said Cyr-Racine.
One of the priorities in the P5 report is a cosmology experiment that uses telescopes in Chile and at the South Pole, CMB-S4. This cosmic microwave background (CMB) project is the fourth generation experiment of its kind (hence S4). This top priority represents an essential evolution for particle physics, a scientific field for building large particle accelerators. The report also positions the U.S. to potentially host a muon collider, a novel experimental facility that could open the next high-energy frontier in particle physics.
“There is a lot we can learn about particle physics from cosmology and by looking at the night sky. The top priority for this decade is actually to build telescopes that can observe light from the very, very early universe to answer important questions about particle physics. This is an interesting evolution of priorities for the field in the next decade. Beyond that, the report lays the groundwork for the U.S. to host a future state-of-the-art particle collider,” explained Cyr-Racine.
While UNM had a significant presence in the P5 report, UNM’s Professor Sally Seidel became the interim chair of the HEPAP, which is the committee that evaluates (and, in this case, approves) the P5 report on behalf of the U.S. particle physics community.
“U.S. particle physics research right up to the present day has positioned our country as a leader and strong international partner in seeking answers to a wide variety of absolutely fundamental questions about how nature works,” said Seidel. “This report is the culmination of a community-driven process, distilling input from literally thousands of particle physicists, to recommend the best research directions to pursue next, to explore the most important scientific questions that our field can pose.”
The previous P5 report designed a compelling program that led to constructing necessary research infrastructure, developing new experimental techniques, and refining our leading theories. The resulting discoveries inspired and trained thousands of young people in scientific inquiry. Seidel explains, “This report builds upon that success. Experimental and theoretical research stimulated by the previous P5 recommendations answered questions and opened doors to new ones that we are eager to investigate.”
Cyr-Racine is a theorist in particle cosmology, a research field that uses observation of the cosmos to learn about particle physics. As a theorist, he builds models to explain night sky observations, allowing him to extract information about particle physics from such data. He explained that he is very grateful for this opportunity as it opened his knowledge to topics beyond his immediate field of study.
“I've learned a lot during this process. For someone at my career stage, this was a very formative experience. I got to learn things about particle accelerators, detectors, and cutting-edge technology, topics that I didn’t know a lot about because that's not what I do on a daily basis,” said Cyr-Racine. “In terms of my research, being on P5 has opened new horizons as it triggered many ideas for new projects. So it has been an extremely positive experience for me and my career.”
Seidel concluded, “In the course of my own scientific career, I cannot recall a more exciting time to explore particle physics. What has been learned in the past 10 years has thrown open to us so many mysteries and puzzles. And at the same time, it has revealed astonishing beauty in the way nature seems to be put together. It inspires my teaching. The process that led to the P5 report, one that brought together thousands of particle physics researchers, from all parts of our country, from many backgrounds, with countless extraordinary ideas --- it is a remarkable display of curiosity, a driver of human progress.”