If you are looking for unknown things, you usually do not know which way to go to find the unknown. This dilemma is also faced by scientists who want to advance into previously unknown areas of elementary particle physics. And yet they have to find a consensus on which experiments promise the greatest gain in knowledge in the next years and decades. For this purpose, the Swiss particle physicists are currently working on a new research roadmap.
It's 14 years ago when particle physicists at Swiss universities and research institutes for the first time established a roadmap. The 96-page document bore the sober title 'Status and Outlook of Research and Education'. The authors presented current research activities at Swiss universities and the Paul Scherrer Institute (, Villigen / AG). In addition, they agreed on a range of larger and smaller experiments in which Swiss researchers would participate in the coming years and decades.
Focuses in cutting-edge research
Although Switzerland has a significant participation at the forefront of science in a lot of research activities despite being a relatively small country, one cannot contribute to every research initiative worldwide. Particle physics derives its legitimacy - in addition to activities in the theoretical field - on the power of the experiment. The experiments including the related infrastructures today are often constructed and operated by huge collaborations requiring significant resources. Accordingly, the Swiss researchers must agree on certain priorities in which they want to contribute to cutting-edge research.
When the roadmap appeared in 2004, such a focal point was the upcoming research on the new CERN particle accelerator for example: The Large Hadron Collider () was under construction at that time and was expected to be operational within a few years. In 2009 the LHC actually begun his first run, and three years later, the high energy physicists made headlines with the discovery of the Higgs particle. With the LHC, they had detected the particle that the Briton Peter Higgs and other theoretical physicists had predicted in 1964 already.
Time for a glimpse into the future
The 2004 roadmap has not become superfluous with the Higgs discovery, as the LHC will run for another two decades and - hopefully - will continue to provide ground-breaking insights into the world of elementary particles. Nevertheless, this example shows that particle physicists have to adapt their strategic goals to the current state of research at regular intervals. "Since the last roadmap, about 15 years have passed. Today it is time to look into the future and to redefine which research work and experiments we want to join as Swiss particle physicists, "says Prof. Michele Weber, member of the Executive Board of CHIPP (Swiss Institute of Particle Physics), the umbrella organization that assembles all particle physicists working in Switzerland, including the astroparticle physicists.
According to Michele Weber, it is not a given that the actors in a field of research as diverse as particle physics are able to sit around a table and fix the future focus of work in a discursive process. Exactly this task was done in the early April by close to one hundred scientists. They met at the SBB conference center 'Center Loewenberg' near Murten for a one-week workshop. Bruno H. Moor, Head of the Department for International Cooperation for Research and Innovation in the State Secretariat for Education, Research and Innovation (), spoke at the beginning of the workshop. Switzerland is proud to be a host state of CERN, Moor said, and pointed out its importance in the Swiss science landscape together with CHIPP and its Roadmap. He encouraged the assembled scientists to set up the priorities of future scientific work. This also creates the basis for important financing contributions by SERI and other public funders.
Insight into three subdisciplines
Particle physics consists of three pillars: the first one covers the physics related to the experiments done with very high energy and/or intensity beams. The outstanding research institution of high-energy physics is CERN, while high intensity experiments at low energy in Switzerland has a permanent home especially at PSI. The second pillar is neutrino physics. It deals with the nature of neutrinos, electrically neutral and difficult to detect. The neutrinos were recently discovered to have mass, a fact that challenges our theories and opens the way to a long-term program of researches. Finally, the third pillar is astroparticle physics. This subdiscipline examines astronomical issues by focusing the attention not primarily on galaxies and stars, but on cosmic particles.
At the workshop in Murten, representatives of the three subdisciplines informed about the ongoing work on several dozen experiments involving Switzerland. At the same time, they sketched out the experiments and facilities being considered for the coming years and decades, on which physicists currently are working conceptually but also through the construction of subcomponents. "These presentations and related discussions served to pinpoint our position," says Tatsuya Nakada, the Chairperson of the CHIPP Executive Board. "Murten was the starting point of an intensive discussion process, which will culminate in a second workshop in September and finally will lead to the new Roadmap. The roadmap is important beyond the borders of Switzerland, since it is at the same time the input of Swiss particle physics to the European Strategy for Particle Physics, which is to be adopted by the CERN Council in the spring 2020. The European Strategy will be of existential importance for the further development of CERN. "
When the LHC goes out of service
A lot of work in the ongoing strategy process is still ahead of the particle physicists. In particular, this includes the delicate task of choosing from the bunch of interesting research approaches and experiments that enable Swiss researchers to optimally apply their know-how. How demanding these decisions are may be exemplified by the question of which large-scale research facility the high-energy physicists want to rely on when the LHC is expected to go out of service in 2035. Alain Blondel pleaded for the Future Circular Collider (at the workshop in Murten. This is a 100 km long, ring-shaped tunnel, which could – according to the vision – offer the broadest research program, by hosting, in succession or not, an electron-positron collider of very high luminosity and precision but relatively low energy up to 400 GeV, and/or – when powerful 16 Tesla magnet would become available – a 100 TeV proton-proton collider. When completed, the FCC with its 100 TeV will provide a seven times higher collision energy than the LHC.
According to information from Blondel, on which the idea of the FCC goes back significantly, the new accelerator of the top class in the first stage, for example, could be used for the further characterization of the Higgs boson and a wide range of other research issues, including possibly the evidence of heavy, right-handed neutrinos. After full construction, it would then even be able to gain knowledge about the interaction of two Higgs particles, which is a unique property of these particles.
Despite such tantalizing prospects, the construction of the FCC is far from being decided. The technical hurdles are high, and the funding of the mulri-billion Euro project is still in the stars. In addition, the project has to be evaluated together with options for linear accelerators being considered in Japan (International Linear Collider / ) and CERN (Compact Linear Collider / ). Not to mention the ambitions of China, which is said to want to prove its reputation as a science power with the construction of a large accelerator similar to FCC. Finding the right path in such a mix of technical, financial and political arguments is extremely demanding. Swiss particle physics is facing months of very challenging discussions. Doing that the community of particle physics and astroparticle physics shows its strength to go through such a process under the umbrella of CHIPP.
Author: Benedikt Vogel