The CERN Council has released the recommendations of the European Strategy for Particle Physics. These were finalised in early December during a session in Ascona, Switzerland.
For the new update of the ESPP strategy, the CERN Council has asked a working group for advice on the most desirable successor to the current LHC accelerator in Geneva, and possible alternatives if that plan proves unfeasible or impractical. Other topics such as astroparticle physics are also on the agenda.
The particle strategy update has been underway since 2024 and is a bottom-up project in which the community of researchers and institutes jointly formulate a plan for the future. Nikhef is closely involved in this process on behalf of the Netherlands. Director Jorgen D’Hondt was one of the authors of the drafting session of the European Strategy Group in Ascona.
In the draft version of the particle strategy drawn up in Ascona, the FCC (Future Circular Collider) with colliding electrons and positrons is designated as the best successor to the LHC as the new flagship collider for CERN.
FCC-ee is a circular superconducting particle accelerator with a circumference of over 90 kilometres, located underground southeast of the particle laboratory in Geneva.
According to its authors, this FCC-ee offers the most opportunities for a visionary research programme into open questions in particle physics, particularly those surrounding the Higgs particle. It also opens up opportunities for discovering new physics beyond the Standard Model. Furthermore, FCC will lead to the development of new technology that is also socially relevant.
According to the ESPP recommendation, the first alternative to this design is a slimmed-down version of the same FCC accelerator. In this version, only two detectors are built into the ring instead of the intended four, the intensity of the beams is lower, and the proposed top quark research is omitted. Construction costs are therefore estimated to be 15 per cent lower.
Previously, there were also ideas for other versions of plan B, ranging from an advanced electron-electron machine in the current LHC tunnel (LEP3) to an electron-proton collider, a linear accelerator and a muon accelerator.
In the assessment of the ESPP working group, all of these alternatives either have too little potential for interesting new physics, or are still too uncertain technically to serve as a flagship for CERN.
The CERN Council will study the recommendations over the coming months and will announce its decision on the strategy in May during a special meeting in Budapest. The Netherlands is one of CERN’s partners and a member of the Council. Officially, the Netherlands has not yet taken a position on the recommendations.
