What CERN’s Future Circular Collider could mean for the world of Physics

Let’s start with the question that you are probably considering right now — “What is the Future Circular Collider, and why would I care about it?”

The Future Circular Collider (or FCC) is a conceptual particle accelerator that has been conceived with the aim of succeeding the Large Hadron Collider (LHC). But why is this important? Let’s just say that the LHC is currently the largest machine in the world and, at a cost of approximately 10 billion dollars, the second most expensive experiment ever built (the most expensive being the International Space Station). Imagine a machine that is designed to replace the LHC.

The FCC, if built, is estimated to be 100 kilometres long (almost 4 times larger than the LHC) and at a maximum energy of 100 TeV¹, is expected to collide particles 10 times faster than the LHC. Now, given that the FCC is supposed to be so much better than the LHC, why did I use “if built” instead of “when built” while talking about its construction? The simple reason is that the FCC is estimated to cost 20–22 billion dollars, and people are asking whether investing in another large collider is worth it. Moreover, some physicists are concerned that the collider might not even help us learn anything substantial.

The Large Hadron Collider was inaugurated in 2008, with the first beam circulated on 10th September 2008. It was built and is operated by CERN (the European Organisation for Nuclear Research). Former CERN Director Robert Aymar called it a “marvel of modern technology”. It consists of a circular tunnel of length 27 kilometres, built 100 metres under the France-Switzerland border, near the CERN headquarters in the Swiss city of Geneva. The actual collider lies within this tunnel and consists of superconducting magnets, which accelerate the two opposite particle beams to a speed comparable to that of light. These two particle beams are made to collide at four locations along the LHC, where four different experiments with particle detectors have been set up — LHCb², CMS³, ALICE⁴, and ATLAS⁵.

The main purpose for which the LHC and other similar particle accelerators are constructed is to help physicists test various theories in the field of particle physics by studying the properties of the different particles emitted by the collision of the beams. The LHC is most famous for the discovery of the Higgs boson, or the “God particle”. On 4th July 2012, physicists at the LHC presented evidence that confirmed the existence of the Higgs boson, a particle that was postulated by Peter Higgs⁶ and Francois Englert⁷ in 1964. It took nearly half a century and the construction of the LHC to confirm the existence of this particle. Why is this important? Only because the Higgs boson is believed to be the particle which gives mass to other particles, and hence to all matter.

But, like all other machines, the LHC too has an “expiry date” of sorts. It is assumed that it would reach the end of its discovery potential after 2035. This is where the theoretical FCC comes in. According to CERN, the goal of the FCC is to “greatly push the energy and intensity frontiers of particle colliders, with the aim of reaching collision energies of 100 TeV, in the search for new physics”. Essentially, CERN wants to build a bigger, more powerful, and way more expensive machine to continue the work of the LHC once it stops working.

However, the question still stands. Is such a complex and expensive project worth it? Aren’t there other areas of science that the same money would be better spent on? Physicists are finding it difficult to provide concrete answers to such questions. All that can be said for sure is that a collider with higher energies (such as the FCC) means a higher probability of finding something new.

Some physicists, in fact, are sceptical of the need for another larger collider such as the FCC. They argue that when the LHC was built, the Standard Model of Particle Physics (the theory that describes the fundamental forces of nature and classifies elementary particles) wasn’t adding up and we had a reason to think that we would discover something new. However, after the discovery of the Higgs boson, the further tests conducted by the LHC have not led to any major discovery. Jared Kaplan, a theoretical physicist at John Hopkins university, says that “the scientific case is weaker than it has been for past colliders”. One of the many mysteries of physics is the evidence for dark matter. Kaplan says, “A lot of the experiments that search for dark matter are $10 million, not $20 billion. It might make more sense to fund a hundred of those experiments than build one collider for 10 times as much money.”

CERN, on the other hand, argues the case for the need of a larger and more powerful particle collider. Director General Fabiola Gianotti has said that the FCC has “tremendous potential” to “improve our knowledge of fundamental physics and to advance many technologies with a broad impact on society”.

Clearly, the debate surrounding the possible construction of the FCC will be a long-drawn one, with physicists and funders arguing over the nuances of the project, until it is either approved or scrapped. But, if the Future Circular Collider is indeed built according to the design conceptualised by CERN, it might truly “inaugurate the post-LHC era in high-energy physics” and “serve the worldwide physics community for the rest of the 21st century”.

Footnotes:

1 — tetra-electron Volt, a measure of energy

2 — the Large Hadron Collider ‘beauty’ experiment

3 — the Compact Muon Solenoid

4 — A Large Ion Collider Experiment

5 — A Toroidal LHC ApparatuS

6 — British theoretical physicist, won Nobel Prize along with Francois Englert for his work on mass of subatomic particles

7 — Belgian theoretical physicist, won Nobel Prize along with Peter Higgs for his work on mass of subatomic particles

References:

“CERN Accelerating Science.” CERN, home.cern/science/accelerators/future-circular-collider.

“CERN Accelerating Science.” CERN, home.cern/science/accelerators/large-hadron-collider.

“CERN Prepares to Celebrate Completion of the LHC.” CERN, home.cern/news/press-release/cern/cern-prepares-celebrate-completion-lhc.

“Future Circular Collider: Is It Worth It?” Future Circular Collider: Is It Worth It? | Laboratory News, www.labnews.co.uk/article/2024887/future_circular_collider_is_it_worth_it.

“International Collaboration Publishes Concept Design for a Post-LHC Future Circular Collider at CERN.” CERN, home.cern/news/press-release/accelerators/international-collaboration-publishes-concept-design-post-lhc.

Piper, Kelsey. “The $22 Billion Gamble: Why Some Physicists Aren’t Excited about Building a Bigger Particle Collider.” Vox, Vox, 22 Jan. 2019, www.vox.com/future-perfect/2019/1/22/18192281/cern-large-hadron-collider-future-circular-collider-physics.