Over the next five years, key events shaping the future of particle physics will unfold. We will have results from the second run of the LHC, and from other particle and astroparticle physics projects around the world. These will help us to chart the future scientific road map for our field. The international collaboration that is forming around the US neutrino programme will crystallise, bringing a new dimension to global collaboration in particle physics. And initiatives to host major high-energy colliders in Asia should become clear. All of this will play a role in shaping the next round of the European Strategy for Particle Physics, which will in turn shape the future of our field in Europe and at CERN.
CERN is first and foremost an accelerator laboratory. It is there that we have our greatest experience and concentration of expertise, and it is there that we have known our greatest successes. I believe that it is also there that CERN’s future lies. Whether or not new physics emerges at the LHC, and whether or not a new collider is built in Asia, CERN should aim to maintain its pre-eminence as an accelerator lab exploring fundamental physics.
CERN’s top priority for the next five years is ensuring a successful LHC Run 2, and securing the financial and technical development and readiness of the High-Luminosity LHC project. This does not mean that CERN should compromise its scientific diversity. Quite the opposite: our diversity underpins our strength. CERN’s programme today is vibrant, with unique facilities such as the Antiproton Decelerator and ISOLDE, and experiments studying topics ranging from kaons to axions. This is vital to our intellectual life, and it is a programme that will evolve and develop as physics needs dictate. Furthermore, with the new neutrino platform, CERN is contributing to projects hosted outside of Europe, notably the exciting neutrino programme underway at Fermilab.
If CERN is to retain its position as a focal point for accelerator-based physics in the decades to come, we must continue to play a leading role in global efforts to develop technologies to serve a range of possible physics scenarios. These include R&D on superconducting high-field magnets, high-gradient, high-efficiency accelerating structures, and novel acceleration technologies. In this context, AWAKE is a unique project using CERN’s high-energy, high-intensity proton beams to investigate the potential of proton-driven plasma wakefield acceleration for the very-long-term future. In parallel, CERN is playing a leading role in international design studies for future high-energy colliders that could succeed the LHC in the medium-to-long term. Circular options, with colliding electron–positron and proton–proton beams, are covered by the Future Circular Collider (FCC) study, while the Compact Linear Collider (CLIC) study offers potential technology for a linear electron–positron option reaching the multi-TeV range. To ensure a future programme that is compelling, and scientifically diverse, we are putting in place a study group that will investigate future opportunities other than high-energy colliders, making full use of the unique capabilities of CERN’s rich accelerator complex, while being complementary to other endeavours around the world. Along with the developments I mention above, these studies will also provide valuable input into the next update of the European Strategy, towards the end of this decade.
Global planning in particle physics has advanced greatly over recent years, with European, US and Japanese strategies broadly aligning, and the processes that drive them becoming ever more closely linked. For particle physics to secure its long-term future, we need to continue to promote strong worldwide collaborations, develop synergies, and bring new and emerging players, for example in Asia, into the fold.
Within that broad picture, CERN should steer a course towards a future based on accelerators. Any future accelerator facility will be an ambitious undertaking, but that should not deter us. We should not abandon our exploratory spirit just because the technical and financial challenges are intimidating. Instead, we should rise to the challenge, and develop the innovative technologies needed to make our projects technically and financially feasible.