ª PARTICLE PHYSICS Deutsches Elektronen-Synchrotron A Research Centre of the Helmholtz Association PARTICLE PHYSICS 2013 2013ª The Helmholtz Association is a community grand challenges faced by society, science and of 18 scientific-technical and biological- industry. Helmholtz Centres perform top-class Highlights medical research centres. These centres have research in strategic programmes in six core been commissioned with pursuing long-term fields: Energy, Earth and Environment, Health, and Annual Report research goals on behalf of the state and Key Technologies, Structure of Matter, Aero- society. The Association strives to gain insights nautics, Space and Transport. and knowledge so that it can help to preserve and improve the foundations of human life. It does this by identifying and working on the www.helmholtz.de Accelerators | Photon Science | Particle Physics Deutsches Elektronen-Synchrotron A Research Centre of the Helmholtz Association Imprint Publishing and contact Editing Deutsches Elektronen-Synchrotron DESY Ilka Flegel, Manfred Fleischer, Michael Medinnis, A Research Centre of the Helmholtz Association Thomas Schörner-Sadenius Hamburg location: Layout Notkestr. 85, 22607 Hamburg, Germany Diana Schröder Tel.: +49 40 8998-0, Fax: +49 40 8998-3282 Production [email protected] Monika Illenseer Zeuthen location: Printing Platanenallee 6, 15738 Zeuthen, Germany Druckerei Heigener Europrint, Hamburg Tel.: +49 33762 7-70, Fax: +49 33762 7-7413 [email protected] Editorial deadline 28 February 2014 www.desy.de ISBN 978-3-935702-87-4 Editorial note doi: 10.3204/DESY_AR_ET2013 The authors of the individual scientific contributions published in this report are fully responsible for the contents. Cover A possible design of CTA, the Cherenkov Telescope Array. Reproduction including extracts is permitted subject to crediting the source. (Credit: G. Pérez, IAC) This report is neither for sale nor may be resold. PARTICLE PHYSICS 2013ª Highlights and Annual Report 2 | Contents Contentsª º Introduction 4 º News and events 11 º Research topics 23 º References 105 Contents | 3 The year 2013 at DESYª Chairman’s foreword 2013 was very busy for DESY. In the last years, DESY has most heart of the facility, and the successful implementation of their successfully brought about many new projects, such as the industrial series production once again underlines DESY’s European XFEL X-ray laser, the new FLASH II free-electron laser competence in accelerator R&D. Cavity performance tests at facility and the extensions of the experimental hall of the PETRA III DESY proved that the required technical specifications were met synchrotron radiation source. In parallel to the development of or even exceeded, which is also an interesting technological new user facilities, new research centres are being established achievement for future linear accelerator and collider projects. at DESY that exploit the unique properties of the DESY light The European XFEL will emit first laser light in 2016. sources, such as the interdisciplinary Centre for Structural Systems Biology (CSSB). All these projects are now under 2013 was also a very successful year in particle and astroparticle construction, shaping the current picture of the DESY campus. physics. The clear highlight of the year was the discovery of the first high-energy extragalactic neutrinos by the IceCube neutrino The construction of the European XFEL X-ray free-electron laser telescope at the South Pole. The much-acclaimed discovery is DESY’s top-priority endeavour. DESY contributes significant is a marvellous success in neutrino astrophysics, celebrated resources to this international prestige project. The super- worldwide as a scientific breakthrough of the year 2013. DESY conducting niobium cavities devised by DESY are at the is a very visible partner in the IceCube consortium and very DESY's expertise is essential to the IceCube neutrino telescope at the South Pole, whose discovery of extragalactic neutrinos was selected by Physics World as breakthrough of the year 2013. 4 | Introduction The underground construction for the European XFEL X-ray laser was completed in June 2013. From left to right: Helmut Dosch (DESY), Stephan Hebgen (ARGE Tunnel XFEL), Dorothee Stapelfeldt (Senator for Science Hamburg), Christian Scherf (DESY), Beatrix Vierkorn-Rudolph (Head of the Directorate for Large Facilities and Basic Research, BMBF), Claudia Burger (European XFEL) and Massimo Altarelli (European XFEL). proud of this scientific achievement. In the field of gamma also at DESY for the restart of LHC operation in spring 2015. astronomy, DESY is currently devoting considerable efforts to Moreover, DESY is currently preparing components for get the new Cherenkov Telescope Array (CTA) up and running, installation in the coming years and in particular during the next an international gamma-ray observatory that will provide novel long LHC shutdown in 2018. In parallel, several DESY groups insights into the depth of the non-thermal high-energy universe. are carrying out intensive R&D work for major upgrades of the High-energy gamma radiation is produced during cosmic events detectors for the high-luminosity phase of the LHC. of tremendous violence, such as supernova explosions. This new observatory will enable the investigation of largely Along with other Helmholtz centres within the research field unexplored energy ranges from 100 GeV to some 10 TeV with “Structure of Matter”, DESY has been very busy in 2013 unprecedented sensitivity. Focusing the scientific programme formulating its research plans for the upcoming Helmholtz of DESY in Zeuthen on this large-scale international funding period 2015-2019, which will enable DESY to project bears fruits in the potential privilege to host the CTA continue all its ambitious activities. I am confident that we will headquarters. convince the international reviewers of the outstanding quality of our programme. The Nobel Committee awarded the 2013 Nobel Prize in Physics to François Englert and Peter Higgs for their theory explaining the mass of elementary particles. In the prize announcement, the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland, were explicitly mentioned for their significant contributions to the understanding of the origin of mass and in particular for their discovery of the Higgs boson. DESY was involved at several points in this discovery, among others with several Helmut Dosch junior research groups. Right now, preparations are under way Chairman of the DESY Board of Directors Introduction | 5 Particle and astroparticle physics at DESYª Introduction The year 2013 was remarkably eventful for particle and astroparticle physics at DESY. The new particle discovered in 2012 at CERN’s Large Hadron Collider (LHC) was identified as a Higgs boson, and consequently the fathers of the Higgs mechanism, Francois Englert and Peter Higgs, were awarded the 2013 Nobel Prize in Physics. Other projects in particle physics, like the planned International Linear Collider (ILC) or the Belle II experiment at the SuperKEKB collider in Japan, reached major milestones and received considerable attention. In astroparticle physics, the confirmation of extragalactic neutrinos, as discovered by the IceCube neutrino telescope at the South Pole, presented a major achievement. In parallel to all the work leading up to these physics successes, DESY has Francois Englert and Peter Higgs, Nobel laureates in physics 2013, together with the been preparing for the next five-year funding period of the Swedish Royal family during the prize ceremony (Courtesy: © Nobel Media AB 2013, Helmholtz Association, which will start in 2015. Photo: Alex Ljungdahl) In May 2013, at a special meeting at the European Commission in technical and financial basis for such a major endeavour. Brussels, the CERN Council adopted the updated European Strategy for Particle Physics. This strategy defines a clear path The data and the knowledge acquired at DESY’s former into the future, with the full exploitation of the LHC, including HERA collider on the proton structure prove more and more the high-luminosity phase reaching into the 2030s, and the ILC important for LHC analyses. We are therefore happy to see among the highest-priority projects. This strategy is fully in line eminent progress in combining the corresponding efforts at with DESY’s plans for particle physics as laid down in the both colliders. The completion of the HERA data analysis is proposal “Fundamental Particles and Forces” for the third period progressing well, and several key measurements were of the Helmholtz Association’s Programme-Oriented Funding published. Particular emphasis is now on the combination of starting in 2015. This proposal rests on a triangle formed by the results from the H1 and ZEUS experiments. The HERA DESY’s main activities: the LHC, experiments at electron–positron collaborations are preparing to preserve their data in a way to colliders (ILC and Belle II) and a strong theory group. enable analysis of their unique data set also in the future. With the discovery of a Higgs boson, the LHC has taken but its The ILC saw two major achievements in 2013. First, the first step. Although so far all measurements of the new technical design report for this next large-scale project in particle’s properties indicate its compatibility with the Higgs particle physics was published – a step with which the mandate boson of the Standard Model of particle physics, more data of the Global Design Effort ended. The GDE is succeeded and higher centre-of-mass energies are needed to fully by the Linear Collider Collaboration, which combines under its establish the character of the particle. To this end, DESY roof all efforts worldwide towards the realisation of an electron– scientists and technicians are working tirelessly with their positron linear collider. DESY scientists are playing leading roles colleagues in the LHC collaborations on preparations for the in this global effort. Also in 2013, the Japanese high-energy LHC Run 2, which will begin in spring 2015, and on the physics community selected a potential construction site for the necessary detector upgrades.