Skip to main content

Defining the next decade of US particle physics

The “Snowmass” process seeks to identify the most promising questions to explore in future research.

Next week, scientists with connections to US particle physics will make their morning coffee, boot up their computers, and log in to a virtual community planning meeting with about 2000 colleagues. The four-day gathering will set the stage for a process known as Snowmass, during which scientists will develop a collective vision for the next decade of US particle physics research.

“Defining the most compelling questions in particle physics and identifying opportunities to address them in a global context—that is the goal of Snowmass,” says Young-Kee Kim, chair of the American Physical Society’s Division of Particles and Fields, which manages the community planning process.

The process originated in the 1980s, as massive collaborations whose work spanned many years took a central role in particle physics research. The first Snowmass was a three-week meeting in Snowmass, Colorado. In subsequent years, the process expanded significantly to include several meetings over the course of the year. This year’s Snowmass, which has been entirely virtual so far, kicked off in April and will culminate in a 10-day summer study, scheduled to take place at the University of Washington in July 2021.

“The outcome of that summer meeting is a long report, hundreds of pages, that outlines what the community priorities are for the next decade,” says Bo Jayatilaka, co-chair of the Scientist Advisory Council at the US Department of Energy’s Fermi National Accelerator Laboratory and one of the organizers of this year’s community planning meeting.

Based on the report, an advisory committee of scientists called the US Particle Physics Project Prioritization Panel will put together a list of investment priorities for the agencies that fund US high-energy physics research.

The European particle physics community recently completed the European Strategy for Particle Physics in a similar process. Many who participated in that process, including CERN Director-General Fabiola Gianotti, will take part in next week’s Snowmass meeting as well.

The last Snowmass summer study took place in 2013. Now is the time for a new Snowmass proceess, Jayatilaka says, “because a lot of the projects that came out of the last Snowmass process have come to fruition or at least come to an initial concept, design and construction.”

This year, the topics for discussion are divided into 10 thematic “frontiers” representing the various facets of modern particle physics research: energy, neutrinos, precision, the cosmos, theory, accelerators, instrumentation, computation, underground facilities and community engagement. In a new part of the process, researchers were invited to submit two-page letters of interest outlining ideas to discuss at the community planning meeting and beyond. The organizers received over 1500 such letters.

Scientists originally planned to hold the community planning meeting in person at Fermilab. But due to COVID-19, it will instead take place entirely online.

The shift in format presents challenges not faced during previous Snowmass gatherings, Jayatilaka says. “There’s a lot of discussion that happens outside of the formal agenda of these meetings. A lot of new ideas are often born just on the back of a napkin at lunch.”

Kim says that the organizers have “put a lot of thought and effort” into generating opportunities for these informal discussions online. Themed chat rooms are already active, and the formal sessions will be interspersed with gatherings in virtual break rooms.

One benefit of the virtual format is that it will allow researchers based outside the United States to attend without having to deal with an international trip. “Their participation is very important because particle physics is global and we cannot do it by ourselves,” Kim says.

Early-career researchers—graduate students, postdocs, junior faculty and lab scientists—are also taking an active role in the proceedings.

“We are the backbone of any experimental and theoretical efforts” that arise from the Snowmass process, says Vishvas Pandey, a postdoc at the University of Florida who is based at Fermilab. “It’s important that we are involved in the process that lays out the scientific vision for the future of the field.”

Working groups for each of the frontiers include representatives from the early-career community. Pandey co-leads the early-career researchers in the Neutrino Physics Frontier and co-organizes biweekly meetings to gain the input of the broader early-career neutrino community. “We want to encourage all our early-career colleagues to be engaged in the process because our voices are critically important,” he says.

The discussions in the Snowmass process will extend beyond scientific topics: Subgroups organized under the Community Engagement Frontier will make plans related to diversity and inclusion, public education and outreach, and other intersections of particle physics and society. CEF leaders will conduct a special session during next week’s community planning meeting dedicated to social impacts of science.

“I think there will be much greater engagement on those topics than in past Snowmass studies,” Jayatilaka says. “And personally, I think it’s necessary that this happens because we, as scientists, are human beings, and we’re part of the society we live in.”

Particle physicists have learned much about the universe since the first Snowmass back in 1982. Yet from the identity of dark matter to the subtleties of neutrinos, many mysteries remain.

“Every cycle brings different challenges,” Jayatilaka says. “And there’s always unanswered questions that could use ideas on what to build and what to study next.”