In a new open-source study, they conclude that the proposed European particle accelerator FCC-ee does not primarily need to be more powerful than existing machines, but rather more precise.
The so-called Future Circular Collider (FCC-ee) is a planned underground accelerator with a circumference of approximately 90 kilometers. Unlike the current Large Hadron Collider (LHC) at CERN, which collides protons at extremely high energies, the FCC-ee would use electrons and positrons. These collisions are much “cleaner,” allowing researchers to measure what happens during a collision with greater accuracy.
Change of course for physics
According to Professor of Theoretical Physics and Nikhef researcher Juan Rojo, this represents a significant change of course for physics. “We need to unlearn thinking solely in terms of greater and higher energy when it comes to the discovery of new particles,” he says.
Although the FCC-ee delivers much less energy than the current LHC in Geneva, the researchers believe the machine could be of great value precisely because of this. The precise measurements make it possible to detect extremely small deviations in known physical processes. Such deviations can indirectly point to the existence of as yet unknown particles or laws of nature.
That is a different approach than what particle physics has relied on for years. Until now, the emphasis has been primarily on directly producing new, heavy particles by making collisions increasingly powerful. The new study shows that subtle quantum effects may be able to reveal just as much about unknown physics as brute force.
The researchers use so-called “effective field theories” for this purpose—models that allow scientists to calculate how invisible or as yet undiscovered particles still produce measurable effects. According to the authors, the FCC-ee offers a unique opportunity to systematically investigate those indirect signals. Transparent Research
An important part of the study is that all calculations and simulations are available entirely open source. With this, the researchers aim to increase transparency and give other scientists the opportunity to independently verify the results or calculate alternative designs. This is notable, as many previous studies into future accelerators were difficult to reproduce.
The timing of the research is opportune. On May 22, the CERN Council will discuss the future of European particle physics in Budapest during the strategic review of the field. If the member states opt for the FCC-ee, a new phase will follow in which funding, design, and construction must be further developed.
The outcome of that decision could have major consequences for science in Europe. The FCC-ee would not only become one of the largest scientific infrastructure projects ever, but would also determine how researchers will search for answers to fundamental questions about matter, energy, and the origin of the universe in the coming decades.
Photo: CERN