A new update of the European Strategy for Particle Physics (ESPP) is currently being prepared and is set to be finalised in 2026. It means that there are many pivotal dates this year that will shape the update and, in turn, the future of particle physics at CERN and in Europe. The first of those is the deadline for input to the update from the science community, set for March 31.
A key takeaway from the new update will be to recommend a preferred option on a new particle accelerator to serve future scientific investigations into elementary particles and how they interact, building on the 2013 confirmation of the existence of the Higgs boson particle. This recommendation will be taken into consideration by the CERN Council, which will have the final say on any project.
The strategy also has a wider purpose and will provide direction to the European particle physics community on promising areas of research, how the particle physics community can work with other scientific fields, how early-career scientists can be supported, what societal benefits can come from particle physics experiments, how the sustainability of accelerator-based particle physics can be improved, and the best ways to engage public in particle physics.
This makes the 2026 update an important document for Europe’s accelerator community.
Why is the ESPP important for the wider accelerator and particle physics community?
The ESPP is updated approximately every five to seven years. It was first set in 2006 and has been updated twice since, in 2013 and 2020.
Each update contributes several important recommendations to steer the direction of particle physics at CERN and in Europe.
The 2013 update announced the high-luminosity upgrade of CERN’s Large Hadron Collider as a top priority. That upgrade is ongoing and is expected to be completed by 2030.
The 2020 update announced, among other recommendations, the need for a feasibility study on a future hadron collider with an electron-positron Higgs and electroweak factory as a possible first stage.
These particular recommendations are centred primarily on CERN, but the strategy has a broader remit and much of its content is relevant to the wider European particle physics and accelerator community.
For example, based on recommendations in the 2020 update, two roadmaps were crafted to set the direction for detector and accelerator research and development in Europe. These roadmaps were developed through the European Committee for Future Accelerators.
The European accelerator R&D roadmap sets out a structure for a coordinated and intensified programme across national institutes and CERN, including key areas for research and technical areas where development is needed. It also sets out how the accelerator community can work with and draw on other scientific fields. Read the full roadmap here.
The 2020 update of the ESPP also advocated for the particle physics community to work on a common policy for open science, following the growing consensus that publicly funded research should be open access. In 2022, CERN published a new policy for open science based on the ESPP update and UNESCO’s recommendation on open science.
Support for early-career researchers was another area highlighted by the 2020 update and which is important for the wider accelerator community. The update stated: “For early-career researchers to thrive, the particle physics community should place strong emphasis on their supervision and training. Additional measures should be taken in large collaborations to increase the recognition of individuals developing and maintaining experiments, computing and software.”
The update also outlined the particle physics community’s commitment to equality, diversity and inclusion. As a result, CERN in 2021 endorsed its “25 by ‘25” nationality and gender strategy. The two principal goals are to increase the percentage of women employed at CERN from 21% in 2020 to 25% by 2025, and to assess the range of nationalities of CERN employees where the concentration of one (or more) nationalities exceeds 25% in any department or departmental group. As of the end of 2024, the percentage of women among CERN’s staff and graduates reached 24.6%.
Another area of the 2020 update relevant to the wider accelerator community is the call for public engagement, education and communication to continue to be “recognised as important components of scientific activity”. As a result, CERN published its 2021 - 2025 communication strategy, much of which can apply to other particle accelerator labs around Europe.
The 2026 update of the ESPP will likely have similar, extended or new recommendations that will also have an impact on shaping the direction of accelerator-based physics in Europe.
What is the timeline for updating the strategy?
The update will be finalised by June 2026.
One significant event this year is the Open Symposium in June, a week-long discussion of the particle physics community on the input to the strategy update and the current status of particle physics in Europe. It is a paid event with registration open until June 13.
What specific input will there be on a future particle accelerator?
A feasibility study, which began in 2021 and looked into the technical and financial feasibility of building a near 100-km Future Circular Collider (FCC) at CERN, is to be submitted as input to the ESPP update by March 31 this year.
A report into the potential of building a Compact Linear Collider (CLIC) and a muon collider will also be submitted as part of the input to the update.
These reports are prepared by different collaborations.
In order to understand which project is the most suitable, a comparative evaluation is also being prepared jointly by the three project leaders and other experts to help make sure the different studies, measurements and information collected can be compared accurately.
The feasibility study and the other reports will be made public, most likely ahead of the Open Symposium in June.
These documents will be important evidence for the CERN Council in their decision for which, if any, future accelerator project to pursue.
Who is contributing to the ESPP update?
The strategy update is a bottom-up process driven by the physics community. Input can come from individual physicists, universities, laboratories, national institutes, particle physics associations, etc. The deadline for this input is March 31 this year.
Countries will also prepare their ‘national input’ to the strategy. These countries can be CERN member states, associate member states or those with observer status and an interest in CERN activities. The final deadline for the national inputs is 14 November this year.
The update itself is usually a short document containing a small number of recommendations. However, the input will also go towards a new edition of the Physics Briefing Book, an extensive document that provides an overview of the latest developments in particle physics. The 2020 version is available here.
What will the ESPP update cover?
One key element of the update will be to provide a recommendation on the preferred option for a future particle accelerator at CERN.
The CERN Council states: “The aim of the strategy update should be to develop a visionary and concrete plan that greatly advances human knowledge in fundamental physics through the realisation of the next flagship project at CERN. This plan should attract and value international collaboration and should allow Europe to continue to play a leading role in the field.”
Some important questions that the update will address are:
- What if China moves quickly on building the proposed Circular Electron Positron Collider (CEPC), which shares similar objectives to the proposed FCC?
- What if the FCC is not affordable?
- Which non-collider projects should have the highest priority at CERN and other laboratories in Europe?
- Which projects outside Europe should CERN and Europe participate in?
- Should CERN contribute to astroparticle or nuclear physics projects and to what extent?
The update also takes into consideration the international community’s strategy on particle physics and will align with, for example, the P5 report, which is essentially the US’ equivalent to the ESPP.
The most recent P5 report, published in 2023, backed US support for the current designs of the FCC-ee (the first phase of the proposed FCC project) and the Japanese proposal for the International Linear Collider.
Who is in charge of updating the ESPP?
The European Strategy Group (ESG), chaired by German physicist Karl Jakobs from the University of Freiburg, will manage the process and writing of the update.
The ESG consists of:
- A four-person strategy secretariat
- A representative of each CERN member state
- A representative of each laboratory in the Large Particle Physics Laboratory Directors Group (LDG), including its chair
- CERN current director-general Fabiola Gianotti
- CERN’s director-general elect Mark Thomson, who takes over the DG position in January 2026
- The chair of the Scientific Policy Committee (SPC) of CERN
- The chair of the European Committee for Future Accelerators
- Invitees: President of CERN Council, a representative from each of CERN’s associate members and observer states, a representative from the European Commission, the chairs of APPEC, NuPECC and ESFRI and members of the Physics Preparatory Group (which prepares scientific input to the strategy update).