Going larger than the Large Hadron Collider: first steps toward a future machine

The Next Steps in the Energy Frontier – Hadron Collider workshop met at Fermilab’s LHC Physics Center in late August. Photo: Reidar Hahn

In 2012, when scientists at CERN’s Large Hadron Collider discovered the Higgs boson, the machine was colliding particles at an energy of 8 teraelectronvolts, or 8 TeV. Just imagine what a 100-TeV collider could uncover.

That’s what more than 80 scientists in the field of particle physics discussed at a workshop hosted by the LHC Physics Center at Fermilab from Aug. 25-28. Such a collider could unlock profound mysteries of the modern era of physics that remain unanswered. The world’s leading experts in accelerators, detectors and particle physics theory gathered to outline how the community could take the “Next Steps in the Energy Frontier” to address these questions.

The global community has put forward two possible initiatives for a 100-TeV hadron collider: one based in Beijing, called the Super Proton Proton Collider, and one based at CERN in Geneva, the Future Circular Collider. If built, such a collider would be the largest ever, capable of probing nature at the shortest possible distance ever explored, 10-18 centimeters.

“No matter what the next few years of experiments — in the lab, underground and in space — will unveil, the direct exploration of the shortest possible distances remains the principal probe of the fundamental laws of nature,” said CERN scientist Michelangelo Mangano. “Preparing for the next step in this endeavor is a duty, and it’s fun!”

It would also be the first particle accelerator to have decisive coverage of exploring a weakly interacting massive particle dark matter candidate. It would also shed light on the mass scale related to the widely discussed naturalness aspects of nature, the asymmetry between matter and antimatter observed in our universe, rare phenomena associated with Higgs boson productions, and symmetry between matter and forces, among other unresolved matters.

The workshop provided a platform where leaders from Beijing and CERN discussed in detail for the first time in the United States the issues attendant in realizing the technology required by such a high-energy collider: strong high-field superconducting magnets, including those that can operate at higher temperatures; precise, fast, high-resolution, radiation-hard silicon detectors only 10 to 30 microns thick; imaging energy-measuring calorimeters; next-generation computing frameworks for trigger systems and analyses and other advancements.

“It was a very special experience to be on the ‘ground floor’ of such a grand, ambitious and worthwhile collective endeavor. The array of theorists and experimentalists at the workshop included the world’s best,” said Raman Sundrum from the University of Maryland.

As with any innovation, these technological advancements will have an impact beyond fundamental research, benefiting industrial fields in R&D and cost. Indeed, a project of this magnitude will require synergies between various initiatives and provide international collaboration opportunities not only within the scientific communities, but also with industry. Members of the particle physics community plan to continue efforts toward a 100-TeV hadron collider, with the United States playing a central role.

“This workshop opens a vision for the future of the study of fundamental interactions that points beyond the coming decade, continuing to follow our passion for science,” said workshop co-organizer Meenakshi Narain of Brown University.

Sanjay Padhi, Next Steps in the Energy Frontier workshop co-leader, University of California, San Diego Distinguished LPC Researcher