Particle physics finds itself in an exciting era; there are strong reasons to expect physics beyond the Standard Model. Even if so far the experimental results on the discovery of a Higgs particle are compatible with the predictions of the SM, a variety of other interpretations is possible, corresponding to very different underlying physics. Identifying the properties of the discovered particle, determining the mechanism that nature has chosen for electroweak symmetry breaking and continuing the search for physics beyond the SM are clearly the top priorities for the coming years in the quest for understanding nature at its most fundamental level.
During the coming funding period, the challenges for the Helmholtz centres participating in the topic Fundamental Particles and Forces in particular are consequently mainly related to the machines and detectors used to tackle the sketched questions which are here presented in chronological order.
Exploitation of the LHC
The LHC is supposed to recommence operations in 2015 after its current shutdown and to increase the luminosity collected so far by about one order of magnitude by 2022, see here. This ambitious goal necessitates smooth operation of accelerator and detectors and the maintenance of the full data taking and analysis chain at the highest levels, challenging the DESY groups which have numerous responsibilities inside the ATLAS and CMS collaborations. Furthermore, keeping up the strong impact on the definition of the physics programme and on the results of the experiments that DESY has gained with its excellent and broad team of junior and senior scientists is no simple task.
The planned upgrades of the LHC and the detectors will require tremendous efforts. DESY, due to its excellent facilities and long-standing experience in large-scale projects, is predestined to take a major share in the work; however, getting the laboratory into the position to actually contribute is a major challenge: the necessary infrastructure to carry out the corresponding installations has to be prepared and the necessary funds for that have to be allocated. In addition, a large-investment proposal for the construction of detectors has been prepared that is attached to this programme proposal in draft form.
Startup of SuperKEKB and Belle II
The preparations towards a startup of the SuperKEKB collider are ongoing, and first beams are expected early in the next funding period. In late 2016, the physics programme with the complete Belle II detector in place is supposed to begin. It is therefore mandatory that the preparatory work on the detector components with DESY involvement are finished in time, the specific challenge being to have the pixel detector and its remote insertion system ready for installation, see here for details. The ambitious physics goal is to accumulate a luminosity of 10 ab-1 around the end of the next funding period.
Paving the way for the ILC
The superconducting RF technology that will be the basis of the ILC has been brought to maturity at DESY, which puts the laboratory in a favourable position to advance the technical aspect of the project. In case of a rapid decision to build the ILC in Japan, DESY would be instrumental in arranging a European consensus on contributions to the project and for building up and maintaining the required infrastructure and expertise for the construction of a share of the 18,000 cavities, see here.
On the side of the experiments to be built at the ILC, the construction of engineering-type detector prototypes and their integration is a challenge to be met in 2015 in order to be prepared for a positive decision on the ILC and for the necessary formation of experiment collaborations out of the existing study groups ILD and SiD.
The challenge for theory
In the proposal for a topic Fundamental Particles and Forces, theory is an indispensable complement to the experimental activities at the LHC and at e+e– colliders. Theory explores the theory space to devise new models, it guides the measurements, suggests new ways to probe nature, and it interprets the obtained data, see here. The specific challenge to theory is to provide predictions that are, at any given point in time, at least commensurate in precision to the results of all relevant experiments and therefore to investigate and employ new methods and tools. In addition, theoretical creativity is required to suggest new models of physics beyond the SM that are still viable and compatible with all experimental observations from elementary particle physics, from astro- and astroparticle physics and elsewhere and that can be tested experimentally. Furthermore, theory needs to maintain its role as a link between the various experimental activities and as a stimulus for the experimental community.