The Particle Physics Project Prioritization Panel is a tongue-twister of a group that pops into existence every five to ten years or so to create the next long-range vision for particle physics in the United States.
“Particle physics is the study, both through experiment and through theory, of the very smallest building blocks of the universe — the smallest particles that we know about, or that we think might exist,” Christopher Monahan explained. “Examples include things like electrons — those are definitely subatomic particles. But also things that are probably less well known, like taus, muons and different kinds of quarks, as well as the Higgs boson: that’s a very famous example.”
Monahan is an assistant professor in William & Mary’s Department of Physics. He’s also member of the latest assembly of the Particle Physics Project Prioritization Panel, which is usually shortened to “P5.”
“It’s not the ‘P5 Panel,’” Monahan says, “because that would be like saying ‘PIN number.’ So, it’s just P5.”
P5 is a temporary subcommittee of HEPAP, the High Energy Physics Advisory Panel, a group jointly formed by the Department of Energy’s Office of Science and the National Science Foundation, the principal federal funding agencies of particle physics research. The last P5 delivered its report to HEPAP in 2014. The current panel is scheduled to deliver its report in October, 2023. Monahan isn’t sure about how or why he was selected to be a P5 member.
“I don’t exactly know. But my understanding is that there was a call for nominations in the fall, and senior members of the physics community in the U.S. submitted nominations,” he said. “They’re looking for a broad array of physicists with experience in particle physics from across the country, covering experiment and theory.”
Monahan added that the P5 membership skews toward mid-career researchers, “the ones who are going to be doing the work in 10 or 20 years.” P5 Chair JoAnne Hewett describes the 2023 panel as a “forward-looking, young group.” The charge to P5 is essentially to assemble a particle-physicist wish list under a couple of different funding scenarios.
P5 will meet at least monthly, beginning in January. Monahan said they’ll draw upon the 2014 report as well as developments in the field since then. The aim is for the report to include a holistic set of recommendations, taking large, medium and small initiatives into account.
Monahan is a theoretical physicist, working with experiments at both Jefferson Lab in Newport News and at the Large Hadron Collider at CERN in Europe. He said that good physics virtually always comes from the close interaction among theorists and experimentalists that generates both focus and understanding of data.
“It’s very easy to fall into the trap of thinking that theory and experiment are really very different, and they absolutely aren’t,” he said. “It’s almost impossible to make sense of what we’re doing, or what the output of the experiment is, without significant theoretical input and understanding.”
Joseph McClain, Research Writer