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Design of a pan-European Infrastructure for Large Apparatus studying Grand Unification, Neutrino Astrophysics and Long Baseline Neutrino Oscillations

Final Report Summary - LAGUNA-LBNO (Design of a pan-European Infrastructure for Large Apparatus studying Grand Unification, Neutrino Astrophysics and Long Baseline Neutrino Oscillations)

Executive Summary:
The LAGUNA-LBNO project (Design of a pan-European infrastructure for Large Apparatus studying Grand Unification and Neutrino Astrophysics for Long Baseline Neutrino Oscillation) addresses the feasibility of a new European research infrastructure hosting a deep underground neutrino detector, much larger and more sensitive than those presently in operation, for fundamental research in astrophysics and particle physics.
The scientific goals of LAGUNA are to expand the frontiers of particle and astrophysics with extended scientific capabilities, such as the determination of the neutrino mass pattern, the understanding the origin of matter dominance in the Universe, the execution of a broad neutrino astrophysics program with a new detection technology, and searches for new physics at the energies beyond the reach of the LHC at CERN.
Long baseline neutrino oscillation physics is a high-priority item in the roadmaps of high-energy laboratories such as CERN in Europe, Fermilab in USA and KEK in Japan. The LAGUNA observatory in Europe coupled to a neutrino beam from CERN or Protvino will hence attract the worldwide scientific community, offering a unique possibility of shedding light on the fundamental interactions in Nature and on the birth of the Universe via profound cosmological consequences such as the origin of the matter in the Universe. It will further explore our understanding of the fundamental theory of sub-atomic elementary particles called the Standard Model.
The LAGUNA-LBNO design study developed a detailed conceptual design for a most optimal hosting of such a next-generation deep underground neutrino observatory in Europe. All aspects have been considered and a very competitive and solid conceptual design has been obtained. Extremely valuable and extended technical expertise has been gathered and a tight and growing collaboration with industry has developed over many years. Innovative solutions have been developed to optimise technical feasibility and costs in an otherwise challenging underground environment. Three detector technologies (liquid Argon = GLACIER, Liquid Scintillator =LENA and Water Cerenkov = MEMPHYS) have been explored. Three sites were chosen for these investigations: Fréjus in France, Umbria in Italy and Pyhäsalmi in Finland.
The project, coordinated by the Swiss Federal Institute of Technology Zürich (ETHZ, contact rubbia@phys.ethz.ch) involved 40 Partners from academic institutions from Bulgaria, Denmark, Finland, France, Germany, Poland, Romania, Spain, Switzerland, United Kingdom, Russia, and Japan, from international research organisations such as CERN, as well as of industrial partners specialized in civil and mechanical engineering and rock mechanics. Together they have assessed the most accessible way to implement LAGUNA-LBNO in Europe.
The project was subdivided into 5 work packages: two packages focusing on the underground infrastructure, civil engineering, tank construction, liquid handling, and operation, one package on the neutrino beam from CERN, and one on the optimisation of the science programme.
Overall, the LAGUNA-LBNO Consortium has successfully developed a very competitive and solid conceptual design. Extremely valuable and extended technical expertise has been gathered and a tight and growing collaboration with industry has developed over many years. Innovative solutions have been developed to optimise technical feasibility and limit costs in an underground environment.
The LAGUNA Consortium has addressed all aspects necessary for a complete realisation of the project:
(1) the science case
(2) the necessary underground infrastructure & facility
(3) the detector construction sequences and programmes
(4) the large Liquid handling
(5) a detailed costs model
(6) An extensive evaluation and quantification of risks.
CERN has developed the Conceptual Design of a new high-power accelerator neutrino beam directed towards the Pyhäsalmi mine.
The project has very successfully met the goals of the Design Study. Fifteen deliverables with a total of more than 4000 pages have been produced. This very large amount of work performed and extensive material generated is a solid base and an important source of information for future developments worldwide.
The Conceptual Design Phase is now complete and fully documented, and the Consortium is now ready to proceed towards executive plans.
No technical show-stoppers have been found. A staged realisation is favoured to mitigate technical and financial risks, and provides for an early science start.
The LAGUNA-LBNO project was presented in various international scientific conferences: NBI, IPAC, NNN workshop series, High-Power Targetry Workshops and was well received. It represents the European option for the future neutrino experiments. A particularly dedicated attentive effort of the management allowed to nest the results obtained by LAGUNA-LBNO in a wider European and world-wide strategy. Indeed, the results of LAGUNA-LBNO made evident the feasibility of cost-effective next-generation deep-underground neutrino observatory, and become one of the very indicator of the future global neutrino strategy, discussed for instance in the Update of the CERN European Strategy for Particle Physics as well as the European ApPEC Roadmap.

Project Context and Objectives:
The project was subdivided into 5 work packages.
A first work-package performed all necessary tasks to reach cavern and tank designs and their construction plans that allowed for full costing of the construction of the tank facility for the chosen site and detector configurations including risk analysis.
A second work-package made a full assessment of the costs, safety and risks associated with operation of the LAGUNA Research Infrastructure for its full lifetime of >30 years, including initial installation and commissioning of all instrumentation, detector, liquid purification plants. In particular also to identify any show-stoppers or other factors associated with operation, installation and running costs, including potential emergency mitigation, that may impact on the construction phase design and costs and potentially on the site-detector final choice. The results obtained during the earlier stages of the project made evident the need of a partial re-orientation of the research activities in these two work-packages in order to deeply address specific fundamental technical topics. The following aspects of the feasibility of the liquid scintillator option as well as the conceptual design of a liquid argon pilot project, were particularly investigated. Extremely important for the full accomplishment of such investigation was the expertise provided by the industrial beneficiaries Technodyne Ltd, Rockplan Ltd, Rhyal Engineering, Sofregaz as well as the beneficiary Demokritos. This also required a considerable management action in order to allow developing these activities in fully harmonization with the other aspects of the project.
In a third work-package, the neutrino beams from CERN to far detector locations defined by LAGUNA were studied. In particular the option of a new long-baseline neutrino beam from CERN to a far detector located underground in the Pyhasalmi mine in Finland at 2’300 km distance (CN2PY beam) was the focus of the design studies over the reference period. The studied CN2PY-LBNO neutrino beam program extended over two phases using different proton beam sources and parameters:
• Phase-I, where a 400 GeV proton beam is delivered form the CERN SPS with a nominal beam power of 750 kW, and,
• Phase-II, where a 50(75) GeV proton beam is delivered from a new high-power proton synchrotron (HPPS), that is also part of the study, with a nominal beam power of 2.0 MW.
The key design features of the proposed beam scenarios were addressed, with some of the studies going far beyond the conceptual level. The potential of the present CERN accelerators in providing high-intensity proton beam for Phase-I of the project, was confirmed from the studies. Over the reference period, an analysis of the data collected during tests with the high-intensity beams in PS and SPS in December 2012, just before the long-shutdown of the CERN accelerator complex, was concluded. The analysis provided valuable information in further identifying the potential bottlenecks and the required upgrades to the complex in order to sustain the operation of the required high-intensity beams for the neutrino program.
The emphasis was also on the design of the CN2PY beam, starting from the beam optimization, layout options to the engineering concepts of the various components of the neutrino beam and of the new HP-PS synchrotron. All aspects of the proton beams transfer for both options, each involving different technologies and technical challenges, were studied in detail for both the high-energy (400 GeV) Phase-I operation and the low-energy (50 GeV) Phase-II. The neutrino beam optimization was done in collaboration with the Physics work-package (see below) to provide the maximum sensitivity and coverage for the expected physics. A new global multi-parameter method using a generic algorithm was developed to optimize the parameters and layout of the target and the focusing elements (horns). A detailed design of the neutrino beam layout and components, including the underground civil engineering structures and tunnels, the beam equipment inspired from the CNGS technology and experience adopted to the new high-intensity operation, the radiation, environmental and handling aspects of the operation was performed. Optimized solutions for the installation and handling of the various beam components, involving remote handling due to the expected radiation levels were studied. Finally, the detector layout concept and installation of the near detector, located at about 300 m underground was studied to address the key design and operation issues.
Finally, the physics work-package focused on the underground science potential of LAGUNA-LBNO with particular emphasis on the impact of using neutrino beams for long baseline neutrino studies and on astrophysical neutrinos and searches for proton decay. The main objectives were:
• to produce a common and unified simulation of the performance of each detector option, leading to unified studies of the physics reach;
• to assess detector performance for the long baseline neutrino oscillation and high energy neutrino physics areas;
• to perform phenomenological studies of neutrino properties in long baseline neutrino oscillation experiments;
• to consider high energy astrophysical neutrino aspects including atmospheric neutrinos
• to study low energy neutrinos including from supernovae, geo-physical and man-made sources;
• to extend proton decay studies, including assessment of site depth requirements.
Using a common framework, the LAGUNA-LBNO teams studied the detector performance, and specific optimisations were carried out in order to maximise the physics reach. Each of the designs considered in the project have shown to be capable of making an invaluable contribution to our current understanding of the physics of neutrino oscillation, in particular, towards the resolution of the two remaining unknowns of the standard three neutrino oscillation paradigm: the mass hierarchy and the value of the CP phase.

Project Results:
The Consortium has addressed all aspects necessary for a complete realisation of the new LAGUNA research infrastructure:
1. Science case
2. Underground infrastructure & facility
3. Detector construction sequences and programmes
4. Liquid handling
5. Detailed costs model
6. Extensive evaluation and quantification of risks
CERN has developed the Conceptual Design of a new high-power accelerator neutrino beam directed towards Pyhäsalmi.
The underground layout for the LAGUNA-LBNO infrastructure was designed from a multiple point of view, where boundary conditions, present infrastructure, experiment and construction demands and logistics, technical possibilities, construction plans and of course safety issues and risk management were taken into account to optimize a layout solution satisfying all requirements.
The design of the LAr cryogenic vessels was conducted for the different possible sizes of the experiment, 20 kt, 50 kt and 100 kt, taking into account the requested incremental approach by the scientific community. The Study showed that both the baseline tank and the membrane tank technologies are applicable to the LAGUNA LBNO although it was concluded that there are a considerable number of technical benefits to the membrane technology. The design of the LSc tank followed a parallel path. A new design concept was presented which included proposed designs for upper and lower deck structures, proposed methods of construction and associated timelines (so called Classic Design or the Double Deck Tank Design Concept). The report concludes that both options are viable but have differing programme and residual risk implications. The liquid transfer infrastructure design for both LAr and LSc, including the liquid process were conducted and reported.
The LAGUNA LBNO Project Risk Register has evolved over a number of months and with contributions from all Industrial Parties who bring their own particular expertise and experience to the Project.
The general design results of the construction sequences for the LAr and LSc experiments at Pyhäsalmi, including excavation, and the liquid infrastructure as well as the instrumentation, it will take:
° 8 years to realise a 20 kT LAr ready for operation
° some additional 8 years to add a 50 kT LAr ready for operation
° 10 years to realise a 50 kT LSc ready for operation
Construction costs have been calculated. Based on the future update of the PRR the contingency costs of the different experiments will be calculated. The costs calculated so far do confirm the costs estimated expected prior to this LAGUNA-LBNO design study, however reduced greatly the uncertainties associated to them.
The new neutrino beam from CERN has also found to be conceptually feasible. The key design features of the proposed beam scenarios are addressed, with some of the studies going far beyond the conceptual level. The potential of the present CERN accelerators in providing high-intensity proton beam for Phase-I of the project, was confirmed.
From the science aspect, the studies reaffirmed that each of the designs considered in the project have shown to be capable of making an invaluable contribution to our current understanding of the physics of long baseline neutrino oscillations, neutrino astrophysics and proton decay searches.
In conclusion, the Consortium has successfully met the goals of the LAGUNA-LBNO Design Study. The large amount of work performed and extensive material generated is a solid base and an important source of information for future developments worldwide.
A threefold strategy is envisaged towards the implementation phase:
1. Following the Update of CERN European Strategy and coherent with the US P5 vision, explore the North American and Asian options and best exploit the LAGUNA-LBNO studies to help foster a major European contribution to the LBNF facility being developed in USA.
2. Construct and operate the LBNO-DEMO demonstrator at CERN (WA105 project) implementing all the techniques developed in LAGUNA-LBNO and in the context of the neutrino R&D & charged particle beam platform.
3. Develop the plans for an underground PILOT project, to test all the aspects of the underground installation and operation and provide an early physics programme.

Potential Impact:
The LAGUNA-LBNO design study, complementing the first LAGUNA design study also funded within the FP7 Infrastructure scheme, has addressed all aspects necessary for a complete realisation of the new LAGUNA research infrastructure. The scope of the study comprised (1) the science case (2) the realisation of the underground infrastructure and facility (3) the construction sequence of the deep underground neutrino observatory (4) the handling of the liquids (5) the associated financial aspects with a detailed cost book (6) an extensive evaluation and quantification of the risks. In parallel, CERN has development the conceptual design of a new high-power accelerator neutrino beam directed towards the LAGUNA-LBNO observatory.
This study has had a big impact on the ERA and triggered high-level discussions at the CERN Council, at the level of APPEC and APPIC as well as the committees ECFA and ICFA.
In Finland, where Pyhäsalmi is located, the dissemination and societal impact has been the largest, with contacts at the highest ministerial and governmental level.

List of Websites:
http://laguna.ethz.ch/laguna-eu/