by Karen McNulty Walsh
With the discovery of the long-sought Higgs boson at the Large Hadron Collider (LHC), the world’s largest and most powerful particle collider, folks unfamiliar with the intricacies of particle physics might think the field has reached its end. But physicists gathered at the Large Hadron Collider Physics Conference in New York City June 2-7 say they are eager to move forward. Even amid discussions of tight budgets that make some proposed projects appear impossible, the general tenor, as expressed by leaders in the field, is that the future holds great potential for even more significant discoveries.
At a session devoted to reflection and the future of the field, held Friday, June 6, Fabiola Gianotti, a particle physicist at Europe’s CERN laboratory (home of the LHC) and spokesperson for the LHC’s ATLAS experiment at the time of the Higgs discovery, said, “There is challenging work for everyone to make the impossible possible.” In fact, said James Siegrist, Associate Director of the Office of High Energy Physics within the U.S. Department of Energy’s (DOE) Office of Science, “I think the promise of the physics has never been greater.”
Co-sponsored by DOE’s Brookhaven National Laboratory and Columbia University, the week-long meeting featured updates on key findings from the LHC’s four experiments (including a possible hint of new physics), advances in theory, plans for future upgrades, and even future colliders—as well as apanel discussion moderated by Dennis Overbye, a science correspondent for the New York Times.
“We had a very successful conference with more than 300 participants discussing an impressive array of results from the recent LHC run,” said Brookhaven physicist Srini Rajagopalan, U.S. ATLAS Operations Program Manager and a co-organizer of the meeting. He also noted the extremely positive response to an open-to-the-public screening of Particle Fever, a documentary film that follows six scientists during the years leading up to the discovery of the Higgs boson. “I was simply amazed at the public interest in what we do. From young school students to senior citizens, people thronged to watch the movie and continued to ask questions late into the night.”
What keeps you up at night?
At Friday’s panel session, the Times’ Overbye had some questions of his own, perhaps more pointed that the public’s. He asked whether particle physicists’ streak of discoveries could be continued, whether the “glory days” for the U.S. were over, and what keeps physicists up at night. The panelists were realistic about challenges and the need for smart choices and greater globalization. But a spirit of optimism prevailed.
Natalie Roe, Director of the Physics Division at DOE’s Lawrence Berkeley National Laboratory—the first to respond—said, “I’m going to flip the question [of what keeps me up and night] and answer what gets me up in the morning.” Following a long period of experimental and theoretical successes, including the discovery of the Higgs, she said, “this is a very exciting time. There are still a few remaining details … dark matter and dark energy. And these are more than details; they are 95 percent of the universe!” With a long list of techniques available to get answers, she said, there is much work to be done.
University of California, Santa Cruz, physicist Steve Ritz, who recently chaired the Particle Physics Project Prioritization Panel (P5) and presented its recommendations for the future of the field, emphasized the importance of “telling our story,” staging and prioritizing future projects, and “aspiring to a greater program” that continues investments in crucial research and development to lay the foundation for future facilities.
Great technology progress, great challenges
In an overview talk that preceded the panel discussion, Gianotti presented a range of such future projects, including two possible linear accelerators, one in Japan the other at CERN, and two possible circular colliders, one in China and one at CERN. The latter, dubbed FCC, would be a proton-proton collider 80-100 kilometers in circumference—on the scale of the Superconducting Supercollider (SSC) once planned for and later cancelled in the U.S. Such a machine would push beyond the research limits of even the most ambitious upgrades proposed for the LHC.
Those upgrades, planned for data taking in Phase I in 2020 and Phase II in 2025, will begin the exploration of the coupling of the Higgs with other particles to explore the mechanism by which the Higgs generates mass, “electroweak symmetry breaking,” and searches for new physics beyond the standard model and into the realm of dark matter.
But, to really get at the heart of those questions and possibly reveal unknown physics, the scientists say the need for even higher precision and higher energy is clear.
Journey to the dark side
“Our elders had it easy compared to our students,” said Siegrist, describing the physics challenges now open to exploration. He likened this moment in time to the end of a video game his son had played where, “at the end of the game, you end up on ‘the dark side’ and have to start again.” In physics, he said, the dark sector—exploring dark matter and dark energy—is going to be equally challenging to everything that has come before.
To those who say building the future machines needed for this journey is impossible, Gianotti says, “didn’t the LHC also look close to impossible in the 1980s?” The path forward, she emphasized, is to innovate.
“Accelerator R&D is very important,” said Ritz, noting that, “anything we can do to design these machines to cost less” in terms of construction and operation should be done. “We need to be impatient about this,” he said. “We need to ask more and jump in more.”
Panelist Nima Arkani-Hamed, a theorist at the Institute of Advanced Study at Princeton University and Director of the Center for Future High Energy Physics in Beijing, China, likely agrees. He acknowledges the difficult task facing U.S. leadership in high-energy physics. “They are trying to make due with a budget that’s two or three times less than what our vision and this country deserves, and they are doing a good job,” he said. “But I worry that our generation will be viewed as the one that dropped the ball.”
“The sequence of steps for the next few decades is possible,” he added later. “It’s just a matter of will, not technology.”
But because of the scale and cost of future projects, he, like others, emphasized that “we will need the whole world and new pockets of resources and talent.”
The value of collaboration, competition, and globalization
Sergio Bertolucci, Director for Research and Computing at CERN, agreed. “We have been international, but we need to be truly global.”
Such cooperation and competition among nations is good for the field, Ritz emphasized. “We are intensely competitive. We want to be the ones to discover [something new.] But we are also cooperative because we can’t do it alone.”
Panelist Jerry Blazey, Assistant Director for Physical Sciences in the
Office of Science and Technology Policy, DOE’s Siegrist, and others agreed that the LHC is a great model for the field to stand behind and emulate for future collaborative projects. Blazey and Siegrist said OSTP and DOE would work together to discuss ways to smooth the process for such future multinational collaborations and to implement the recommendations of the P5 report.
These include future U.S. work at the LHC, an internationalized Long Baseline Neutrino Facility located at Fermi National Accelerator Laboratory, and a role in Japan’s proposed linear collider, as well as continued investments in the technologies needed for future experiments. Said University of California, Irvine, physicist Andrew Lankford, chair of the High Energy Physics Advisory Panel (HEPAP) to whom the report was delivered, the P5 report describes a field optimized for scientific progress. “It’s a ten year strategic plan—way more than a collection of cool experiments,” he said.
And it emphasizes the value of international competition and cooperation—perhaps one of the biggest successes of particle physics, aside from the breathtaking discoveries. Turning again to the example of the LHC collaborations, Ritz said, “50 years ago some of these people were in countries that were trying to kill one another. Now we don’t even think about what country they are from.”
As Brookhaven’s Rajagopalan summed up, “It is an exciting time for our field as we plan to move forward with ambitious global projects to address the fundamental questions of nature.”
Brookhaven Lab’s particle physics research is supported by the DOE Office of Science.
- Researchers imagine the accelerators of the future
- Physicists Look Beyond the Large Hadron Collider, to the Very Large Hadron Collider
- P5 Report
- Brookhaven Lab Statement on the P5 Report
Karen McNulty Walsh is a science writer in the Media & Communications Office at Brookhaven National Laboratory.