Unveiling the Future Circular Collider: A Vision for 2040 and Beyond

The European Institution for Nuclear Research (CERN), in collaboration with its global partners, has concluded a extensive feasibility study for the ambitious Future Circular Collider (FCC) project. This extensive report,the culmination of years of dedicated effort by over a thousand physicists and engineers worldwide,details the multifaceted aspects of potentially constructing this groundbreaking facility.

The FCC: A Colossal Leap Beyond the LHC

Envisioned as a successor to the Large Hadron Collider (LHC),the FCC boasts a staggering 91-kilometer circumference,dwarfing the LHC’s 27 kilometers. The FCC aims to propel particle physics research into uncharted territories,building upon the pivotal 2012 discovery of the Higgs boson and addressing the many unanswered questions that still plague our understanding of the universe. The LHC, as its launch, has been instrumental in validating the Standard Model of particle physics, but the FCC promises to delve deeper into the mysteries that the Standard Model cannot explain, such as dark matter and dark energy, which together constitute approximately 95% of the universe’s total mass-energy density.

The Enigmatic Higgs Boson: A key to unlocking Cosmic Secrets

The Higgs boson, while seemingly the simplest particle discovered to date, holds profound implications for our existence. It is indeed intrinsically linked to the mechanism by which elementary particles, like electrons, acquired mass in the immediate aftermath of the Big Bang. This mass acquisition was crucial for the formation of atoms and, consequently, all the structures we observe in the universe. Furthermore, the Higgs boson may hold the key to understanding the universe’s ultimate fate and resolving some of modern physics’ most perplexing mysteries.

A Two-Stage Approach: Maximizing Scientific Discovery

The FCC’s proposed research programme is structured around two distinct phases,as outlined in the feasibility study:

1. Electron-Positron Collider: This initial stage will serve as a “Higgs factory,” meticulously producing and studying Higgs bosons,electroweak interactions,and top quarks at varying center-of-mass energies.
2. Proton-Proton Collider: Subsequently, a high-energy proton-proton collider will be constructed, capable of achieving unprecedented collision energies of approximately 100 tev. This will allow scientists to probe the fundamental constituents of matter at an unprecedented level.

The complementary nature of these two stages aligns perfectly with the priorities established in the 2020 update of the European Strategy for Particle Physics, ensuring a comprehensive and impactful research program.

Comprehensive Feasibility: From geology to Socio-Economics

The FCC feasibility study encompasses a wide range of critical considerations, including:

• Scientific objectives and potential discoveries
• Geological surveys and civil engineering requirements
• Technical infrastructure needs
• Territorial and environmental impact assessments
• Research and development (R&D) requirements for both accelerators and detectors
• Socio-economic benefits and overall costs

Financial implications: A Significant Investment in the Future

The estimated cost for the initial electron-positron collider stage, encompassing the tunnel construction and all necessary infrastructure, is approximately 15 billion Swiss francs (approximately 15.89 billion euros). This investment, projected to be distributed over roughly 12 years starting in the early 2030s, includes civil engineering works, technical infrastructure, the electron and positron accelerators themselves, and the four detectors required for operation. Similar to the LHC’s funding model, a significant portion of the FCC’s financing is expected to come from CERN’s existing annual budget.

Lasting Research: Minimizing environmental Impact

CERN is committed to ensuring that any new project exemplifies sustainable research infrastructure. the FCC project will integrate ecodesign principles throughout its entire lifecycle, from initial design to construction, operation, and eventual decommissioning. The report details strategies for minimizing the FCC’s environmental footprint, promoting the development of new technologies for societal benefit, and fostering territorial synergies, such as energy reuse.For exmaple, CERN is exploring innovative cooling technologies that could considerably reduce energy consumption and waste heat.

Optimizing Design and location: Balancing Science and Practicality

A crucial aspect of the FCC’s feasibility study has been the meticulous design and location planning of the collider ring and associated infrastructure. Over 100 different scenarios were developed and analyzed to maximize scientific output while considering territorial compatibility, environmental constraints, construction limitations, and cost-effectiveness. The preferred option is a 90.7-kilometer ring situated at an average depth of 200 meters, featuring eight surface locations and four experimental sites.

Collaboration and Public Engagement

Throughout the feasibility study, CERN has benefited from the unwavering support of its host states, France and Switzerland, in close collaboration with local, regional, and national entities. Moreover, CERN is actively preparing citizen participation processes, in accordance with the respective frameworks of the host states, to ensure a constructive dialog with local communities and stakeholders.

Decision Timeline: Awaiting the Green Light

The feasibility study, while comprehensive, does not represent a commitment from CERN’s member states to actually construct the FCC.The report will undergo rigorous review by self-reliant expert agencies before being presented to the CERN Council at a dedicated meeting in November 2025. The Council is expected to make a decision regarding whether to proceed with the FCC project around 2028. This decision will be a pivotal moment for the future of particle physics, potentially ushering in a new era of discovery.

Beyond Physics: Societal Benefits of Particle Colliders

Particle colliders play a fundamental role in advancing our understanding of the universe. Moreover, they drive the development of cutting-edge technologies with broad societal applications, ranging from superconducting materials for medical imaging and energy-efficient electricity transmission to advanced detectors and accelerators for medical treatments. These technological spin-offs often have a far-reaching impact on various sectors, contributing to economic growth and improving the quality of life.

Contributing to the Future of Particle Physics

The FCC feasibility study was initiated following the recommendations of the 2020 update of the European Particle Physics Strategy. It will serve as a valuable contribution to the ongoing strategy update process, alongside studies of alternative projects proposed by the scientific community, ensuring a vibrant and innovative future for particle physics research.