The Open Symposium on European Strategy for Particle Physics
From 10th to 12th September a very interesting symposium took place in Krakow, to gather input from the community for the Update of the European Strategy for Particle Physics. The symposium was very well attended, with close to 500 participants and was an opportunity for an open dialog between the proponents of the various fields of research in our domain. The meeting also included reports on future plans for the Americas and Asia, in particular the United States and Japan, as well as in the connected field of Astroparticles. Several presentations were also devoted to the role and organisation of Theoretical Physics, of accelerators and detectors development and future challenges in the domain of computing. The slides presented during the meeting can be found at
http://indico.cern.ch/conferenceDisplay.py?confId=182232 .
About 170 papers were submitted to the symposium.
The complete list of submissions can be found at:
http://indico.cern.ch/internalPage.py?pageId=3&confId=175067.
Not surprisingly, the discussion was dominated by the consequence of the discovery by ATLAS and CMS of a “Higgs-‐like” boson at a mass of 125 GeV/c2. The top priority is clearly to understand whether this boson is “only” (!) the missing piece of the Standard Model (“the SM Higgs boson”) or whether its properties depart from those expected from the SM Higgs, which would be the sign of New Physics. This requires measuring with precision the production of th new particle, its spin and CP quantum numbers, its branching ratios into the various decay modes (ZZ, WW, bbar, ττ ,ﾵﾵ) and possibly its self-‐coupling by looking at multiple Higgs.
It is clear that the LHC has a long and bright future. Several speakers recalled that the integrate luminosity of LHC recorded until now corresponds to less than 1% of what can be accumulated over the next 15 years, not to mention the fact that the energy of the machine will be nearlydoubled in 2014, increasing strongly its potential in Higgs physics and in searches for new physics.
However, the subject of many discussions was whether LHC alone is enough or whether a newfacility is also needed. Among those envisaged, one can mention linear or circular e+e‐ colliders, a collider based on circular storage e- rings or even, in the longer term, a ﾵ+ﾵ-‐ circular collider. Linear e+e‐ colliders are the subject of intense R&D and design work by a large community, both at CERN and elsewhere, for more than a decade. In this context, the announcement by Japanese representatives of a consensus reached among the Japanese Particle Physics community to put high priority on a 250 GeV “Higgs factory”, based on a e+e-‐ linear collider upgradable to 500 GeV, and to make in the near future a proposal to their funding agencies for the construction of such a machine with international collaboration, triggered animated debates.
Another important question, which was also the focus of many presentations, is the question of new physics beyond the Standard Model (BSM). Even if it describes very well the phenomena observed until now, the Standard Model cannot be the full answer. For example, it does not explain the striking difference (by 16 orders of magnitude) between the weak scale and the Planck scale, an issue known as the “hierarchy problem”; it does not offer a solution for the Dark Matter needed to explain cosmological observations; it does not explain why neutrinos have tiny but non-‐zero masses etc…
The mass of the Higgs-‐like boson discovered by ATLAS and CMS, combined with the fact that no sign of new particles has yet been seen at LHC, poses great challenges to our theory colleagues. One of the most popular and promising BSM theories is the Supersymmetry (SUSY). In its simplest form (called the Constrained Minimal SuperSymetric Model or CMSSM), SUSY is certainly under pressure, but there is still a very large phase space to be explored. As mentioned above, the LHC potential at its nominal energy will be crucial for this search. The importance and complementarity of flavour physics at LHC (LHCb) and other accelerators (experiments at e+e-‐ B and charm/τ factories, very rare kaon and muon decays experiments, search for a neutron dipole moment with cold neutron sources, more precise measurement of the muon magnetic moment g-‐2) were strongly emphasized to help in this quest.
Hadron physics was also discussed. Understanding the properties of the new state of matter (the Quark Gluon Plasma) created in high energy ions-‐ions collisions at LHC and RHIC was shown to be the top priority of the corresponding community. Measurements at lower energy (SPS ions beams and future ions facilities such as NICA at JINR Dubna in Russia or FAIR in Germany) are also essential to understanding the phase transition between hadronic and QGP states.
Continuous effort on the understanding of the proton structure (including its spin properties) is also needed. This can be done with existing experiments at the SPS, but the proposal for a high energy electron-‐proton collider (LHeC) was also presented.
The European neutrino community also presented its view on the future: on a rather short time scale, a neutrino beam is proposed at CERN SPS in view of a short base line experiment for sterile neutrino search, with a detector moving from the Gran Sasso National Laboratory to CERN. The beam could also be used for R&D and neutrino cross-‐section measurements. In the longer term, a long baseline neutrino beam with a massive liquid Argon detector would be needed for the mass hierarchy and mixing parameter measurements. Such an experiment could also offer a rich astroparticle physics program. An EU-‐funded design study targeted towards this project has been launched in 2011. Since similar goals are pursued in US and Japan, worldwide coordination is obviously needed. Finally, a neutrino factory may be needed in the long term for the ultimate precision measurements of the neutrinos mixing parameters.
Four other topics were also discussed during the symposium.
The crucial role of the theoretical community and the need to continuously favor communication between theorists and/or between theorists and experimentalists were emphasized.
Continuous R&D in the domain of instrumentation and its associated electronics is essential for the success of particle physics in the future.
Similarly, computing is a key ingredient in our field: research to make the most of technological progress in this domain (for example efficient use of multicore processors is absolutely needed.
Finally none of our research would be possible without accelerators and, again in this field, R&D towards future technologies (for example high field magnets or new acceleration technologies) is crucial.
The next steps
The symposium was a first step to gather information from the community. During the next weeks, the European Strategy Preparatory Group1 and the scientific secretaries of the symposium will prepare a “briefing book” based on the information gathered in Krakow.
In parallel, five working groups will also produce reports on more organizational matters. The topics are:
Working mode of the CERN Council for the European Strategy matters
Framework for European participation to a global project and the role of national laboratories and CERN Geneva laboratory.
CERN relations with the European and International bodies such as the EU, ESFRI, and others
Knowledge Transfer and industrial relations
Education, outreach and communication
At a meeting planned for the end of January 2013, all these documents will be used by the European Strategy Group1 to prepare a draft of the strategy statements and of a strategy deliberation document describing the scientific rational for the strategy statements and a possible framework for implementing this strategy.
These will be presented to the CERN Council in its March 2013 meeting for discussion. The final adoption of the updated strategy by the Council is anticipated in May 2013 during a special meeting in Brussels, to coincide with a ministerial-‐level meeting of the European Competitiveness Council.