The spectacular discovery of a Higgs particle at the Large Hadron Collider (LHC) marks the culmination of a several decades-long effort of experiment and theory and opens a new era of elementary particle physics. One of the prime goals within this field, topic Fundamental Particles and Forces, for the coming years will be to study the properties of this new particle in detail and in this way to identify the underlying physics that is responsible for providing elementary particles with the property of mass. The question whether the observed phenomena are compatible with the Standard Model of particle physics or whether they require New Physics beyond the SM touches on the big open issues of the nature of Dark Matter observed in the Universe, of the unification of fundamental forces (and ultimately even gravity), and of the matter–antimatter asymmetry in the Universe. Evidence for physics beyond the SM could arise from the detailed investigation of the properties of the new particle, from other high-precision measurements and from direct searches for new particles.
These endeavours require cutting-edge research on several frontiers:
- Proton-proton physics: The LHC will provide the highest energies and luminosities, thus contributing to our understanding of the discovered new particle and opening up new territory for new phenomena required to solve the open questions of particle physics sketched above.
- Electron–positron physics: The future e+e– machines — ILC and SuperKEKB — will provide the unprecedented precision both for the direct detection of phenomena at high energy or mass scales like Higgs or SUSY (or other extensions of the SM) and for indirect effects of New Physics from high-precision measurements in the electroweak and flavour sector.
- Theoretical physics: The experimental activities need to be well linked with a vital and broad research programme on the theoretical side. This concerns in particular predictions for the possible phenomenology of New Physics, precise predictions for SM processes and the interpretation of the observed results in different frameworks, reflecting the possible variety of their physical origin.
It is therefore on this triangle – LHC physics, e+e– physics, theory — that the topic Fundamental Particles and Forces builds its scientific strategy for the upcoming next funding period and beyond. Two Helmholtz centres — DESY and KIT — participate in the topic Fundamental Particles and Forces. With a share of more than 95%, the topic is dominated by DESY where the entire particle physics programme is financed from Helmholtz funds.
Close connections of the topic Fundamental Particles and Forces to the other topics in the programme Matter and the Universe follow naturally from the above strategy. There are numerous common scientific questions — one example being the origin and nature of the large amount of Dark Matter observed in the Universe. Particle physics colliders offer the potential to directly produce Dark Matter particles and to study their properties. Additional findings in the field of astroparticle physics (topic Matter and Radiation from the Universe) would provide complementary information and enable an important test for consistency with astrophysical and cosmological constraints. The commonality of the topics is further underlined by the common usage of experimental infrastructures — e.g. joint experiments with scientists from the topic Cosmic Matter in the Laboratory are performed in the field of heavy-ion physics at the ATLAS and CMS experiments.
The topic Fundamental Particles and Forces also keeps close connections to the programme Matter and Technologies with its activities in generic detector R&D and in accelerator development, and mutual benefit is expected, more here.
The next funding period will be dominated by the further physics exploitation of the LHC and preparation of the detector upgrades for running until 2030. At the same time, new high-precision measurements at lower energies will be carried out, in particular with the Belle II detector that will be commissioned and will start operation within this period, and a world-wide consensus about the ILC (to be built in Japan) will be sought while finalising the site-specific work on the ILC and the remaining R&D on the detectors. In all three areas, Helmholtz is a major player:
- DESY's role in the operation and the physics programme of the LHC experiments is and will remain central for both ATLAS and CMS. DESY's expertise — building on a long record of successfully running and exploiting large facilities like HERA — is crucial in many places and is widely acknowledged by the LHC collaborations.
- DESY is expected and planning to contribute substantial parts of the detector upgrades which will be implemented during the ensuing long shutdowns. Most notably, it is foreseen to contribute tracker end-caps for the high-luminosity LHC (HL-LHC) for both ATLAS and CMS to be installed 2022 in close collaboration with German universities and international partners. A proposal for a large investment for LHC upgrades has been prepared, see here.
- For the upgraded Belle II experiment in Japan, the German particle physics community is providing a novel pixel detector that is based on the DEPFET technology originally developed for the ILC. DESY is instrumental in providing necessary infrastructure to install, operate and align the entire Belle II vertex detector which will go into operation in 2016.
- Concerning the ILC, DESY is in a unique position: it is the home of the SCRF (superconducting radio-frequency) technology which was chosen for the ILC; it has assembled unique experience with FLASH which served as a technology demonstrator and with the European XFEL which can be viewed as a large-scale prototype of the ILC accelerator. In addition, the laboratory has a central role in the ILC detector development and in the management of both ILC detector proposals, ILD and SiD, where DESY sta scientists act as co-spokespersons.
- The theory activities of DESY are crucial for the success of the experimental programme. The theory groups at DESY and KIT have made key contributions to the physics analyses at the LHC and to the assessment of the physics case of future e+e– colliders, pursuing a close interaction of theory and experiment. The scientific portfolio of the theory activities is such that the newest developments both on the experimental and the theoretical side can be exploited and new lines of research can be triggered, making use of the synergies between its different branches.