This week the European Strategy Group meets in Erice, Italy, to formulate an updated European strategy for particle physics. The last European strategy document was summarized in two pages back in 2006 and established the physics goals of the European program and the R&D necessary for future machines. Since then much has changed.
The LHC has come into its own with outstanding performance and a huge discovery under its belt. It is clearly the machine that will dominate the Energy Frontier for the next two decades. The discovery of what we expect to be the Higgs boson is a triumph for particle physics and gives us a totally new particle to study: the first fundamental particle without spin. This discovery gives impetus to the International Linear Collider, and our Japanese colleagues are well on their way to propose that Japan host the ILC. There are many competing ideas for circular machines, including muon colliders, but none as advanced as the ILC.
The LHC has also produced an astounding number of results showing that various phenomena that lie beyond the Standard Model and that were postulated before the LHC turn-on have not yet been found. This is highly significant since the most comfortable theories prior to turning on the LHC would by now have us swimming in discoveries of new supersymmetric particles. Will the 14-TeV run in 2015, at twice the energy of the current run, bring them forward?
The window for future neutrino physics experiments is now wide open after the results from the Daya Bay experiment revealed the existence of a large mixing angle θ13. This large angle gives rise to many ideas for future experiments, including our Long-Baseline Neutrino Experiment. Results from present-day short-baseline neutrino experiments and reactor experiments do not sit comfortably with the standard three-generations-of-neutrinos framework, so a new crop of experiments will pursue these apparent anomalies. Rare-process experiments are also in demand as one way to investigate whether there are any particles to be found much beyond the reach of the LHC.
Dark energy and dark matter still remain mysterious. Dark energy is consistent so far with a cosmological constant, and there is no convincing evidence yet for dark matter particles. We continue to work harder and more imaginatively to solve these mysteries.
It is a very rich menu indeed that confronts the Strategy Group in Erice and should make for a very interesting week. The group retreating in Erice has the advantage of a comprehensive Physics Briefing Book, produced by the Preparatory Group through a very exhaustive process analogous to the Snowmass community workshops in the United States. It is a superb effort and great summary of the status and opportunities in our field.