A diverse group of about 180 early-career researchers in particle physics (mostly experimental physicists) provided feedback as part of the recent update of the European strategy for particle physics (ESPP). I wanted to share their executive summary and few statistics.
This sentence from the executive summary (see below) expresses the majority sentiment in the particle physics community:
“When continuing on the current path, the field will likely be unable to attract the brightest minds to particle physics.”
In terms of science and technology, I am surprised to see the level of interest in CLIC.
source: [2002.02837] Report on the ECFA Early-Career Researchers Debate on the 2020 European Strategy Update for Particle Physics (arxiv.org)
A group of Early-Career Researchers (ECRs) has been given a mandate from the European Committee for Future Accelerators (ECFA) to debate the topics of the current European Strategy Update (ESU) for Particle Physics and to summarise the outcome in a brief document . A full-day debate with 180 delegates was held at CERN, followed by a survey collecting quantitative input. During the debate, the ECRs discussed future colliders in terms of the physics prospects, their implications for accelerator and detector technology as well as computing and software. The discussion was organised into several topic areas. From these areas two common themes were particularly highlighted by the ECRs: sociological and human aspects; and issues of the environmental impact and sustainability of our research. The following paragraphs summarise the key outcomes.
The ECRs feel that the attractiveness of our field is at risk and that dedicated actions need to be taken to safeguard its future. When continuing on the current path, the field will likely be unable to attract the brightest minds to particle physics. The ESU must therefore include sociological and sustainability aspects in addition to technical ones related to machine feasibility and particle physics research. It is of high priority that funding for non-permanent positions is converted to funding for permanent positions, i.e. fewer post-docs in exchange for more staff. In addition, particle physics should play an exemplary role for sustainable behaviour, being inspirational for both society and other sciences. Overwhelming consensus was reached on the idea to establish a permanent ECR committee as part of ECFA. Such a committee would be able to give a mandate to a few individuals representing the ECRs in various bodies.
Future of the Field
Among the many open questions in particle physics, the ECRs find Dark Matter, Electroweak Symmetry Breaking and Neutrino Physics to be the three most important ones. While being open for future international projects, the ECRs emphasise the importance of a European collider project soon after HL-LHC. Postponing the choice of the next collider project at CERN to the 2030s has the potential to negatively impact the future of the field.
Comments on the Briefing Book
The importance of understanding the Higgs mechanism is already well underlined in the Physics Briefing Book (BB)  and shared by the ECRs. Many ECRs stated their discomfort about the way the full CLIC and FCC programmes were compared, especially by how the different states of maturity of the projects were not taken into account sufficiently. Additionally, the impact of collider projects outside Europe on the straw-man scenarios and therefore on the future of the European particle physics landscape has not been laid out sufficiently.
Human and Sociological Factors
For the ESU to be effective and sustainable, it is imperative to holistically include social and human factors when planning the future of the field. Therefore, the ECRs strongly recommend that future project evaluations and strategy updates include the social impact of their implementation. Specifically, equal recognition and career paths for the various domains of our field have to be established to maintain expertise in the field. The possibility for a healthy work-life balance and the reconciliation of family and a scientific career is a must.
Environment and Sustainability
Large European organisations and laboratories such as CERN have a unique position and responsibility in society. A strong statement from CERN putting the environment and sustainability at the forefront of decision-making, aiming at becoming a carbon-neutral laboratory in the short term future, would have a significant impact. The energy efficiency of equipment and the power consumption of the future collider scenarios are already considered but this should be extended to building insulation and the environmental impact of construction and disposal of large infrastructure. There should be further discussion of nuclear versus renewable energy usage and CERN could and should strive for a higher renewable energy fraction. More considerations should be put on the impact of computing and software resources. Travel and conference schedules should be seriously assessed to reduce the amount of travel and the associated carbon footprint.
Accelerator and Detector R&D
Among the ECRs, 88% are in favour of an e +e − machine as the next collider to be realised. A strong and diverse R&D programme on both accelerators and detectors must be a high priority for the future. On the accelerator side, concerns have been raised about whether the key numbers stated in the BB allow for a fair comparison of the various projects; while concerning the 4 detector side, there was no mention of which technology is suitable for which future project and the level of readiness of each technology.
Computing and Software
Software and computing activities must be recognised not only as means to do physics analyses, but as research that requires a high level of skill. Innovation in physics analysis should strive to minimise the time to produce physics results allowing more person-power to be allocated to areas where innovation and development is truly needed. In an effort towards reducing the carbon footprint associated with travel for work purposes, our community can drive the development of new software for remote meetings, even for large groups of attendants. Furthermore, the researchers are generally in favor of open data and see the need for sharing knowledge and resources with other computing communities.
Electroweak and Strong Interaction
Physics Due to the different demands of electroweak and strong physics, there was no clear consensus in the electroweak and strong interaction physics discussion session as to which future collider should be pursued at this stage. For most Higgs couplings, decay width and electroweak precision measurements, e +e − colliders have a clear advantage. However, this is balanced by the greater precision that proton-proton colliders have for rare Higgs couplings, in particular the Higgs self-coupling. It was noted that e +e − colliders are very appealing due to the shorter timescales and their capability of running at the precise energies required to produce copious amounts of Higgs, W and Z bosons or top quark pairs. This is in contrast to the strong physics discussions, where a clear preference towards a pp or ep collider was voiced. Priority should be put on precision measurements and global fits rather than model-driven searches. Tighter collaboration between theory and experiment would enhance the precision of measurements.
Beyond Standard Model, Dark Matter and Dark Sector Physics
No clear consensus on future collider scenarios was found as different, equally valid, theoretical models can prefer one scenario over the other. However, the ECRs consider the diversification of experiments, building on projects such as Physics Beyond Colliders, as vital for the future of the field and should be pursued with high priority in parallel to the larger projects. Similarly to the discussion on electroweak and strong interaction physics, it is felt that better collaboration between theory and experiment is needed to extract the full potential of future programmes, more focus on this for ECRs (i.e. including more PhD students) is needed in particular.
Flavour, Neutrino and Cosmic Messenger Physics
While the heavy flavour domain benefits from any future collider, numerous specialised smaller experiments in the light sector are needed outside these large-scale scenarios to complete the picture. Real-time observations between connected observatories, for example neutrino, gravitational wave and gamma ray telescopes, will be crucial in the future, and to fully realise the potential in this area synergies with HEP would be vital.
 ECFA Newsletter #3, retrieved from
Click to access ECFA-Newsletter-3-Summer2019-final.pdf
 Physics Briefing Book, CERN-ESU-004, arXiv:1910.11775 [hep-ex]
 Supporting note for briefing book 2020: Towards an update of the European Strategy for Particle Physics, https://cds.cern.ch/record/2705370