Astroparticle Physics
Total Page:16
File Type:pdf, Size:1020Kb
4 Astroparticle physics The European Roadmap © Picture: ASPERA / ESA L.Bret-Novapix www.aspera-eu.org This roadmap was worked out by the Scientific Advisory Committee of ASPERA: Ad M. van den Berg Roberto Battiston Laura Baudis Jose Bernabeu Daniel Bertrand Pierre Binetruy John Carr Enrique Fernandez Francesco Fidecaro Gilles Gerbier Andrea Giuliani Andreas Haungs Werner Hofmann Steven Kahn Uli Katz Paul Kooijman Hans Kraus Antoine Letessier-Selvon Manel Martinez Benoit Mours Lothar Oberauer Rene Ong Michał Ostrowski Sheila Rowan Subir Sarkar Stefan Schönert Günter Sigl Ion Siotis Christian Spiering (Chair) Robert Svoboda Francesco Vissani Lucia Votano Roland Walter 3 Executive Summary Astroparticle physics marks the intersection of astrophy- Gravitational waves sics, particle physics and cosmology. It addresses funda- With Advanced VIRGO, Advanced LIGO and GEO-HF, a mental questions like the nature of dark matter and discovery in the next five years becomes highly probable. dark energy, the physics of the Big Bang, the stability This would open an entirely new window to the Universe. of protons, the properties of neutrinos and their role in We urge the agencies to continue to substantially support cosmic evolution, the interior of the Sun or supernovae as the ongoing and planned upgrades to advanced detec- seen with neutrinos, the origin of cosmic rays, the nature tors. of the Universe at extreme energies and violent cosmic processes as seen with gravitational waves. Dark Matter With the advent of the LHC and thanks to a new genera- Among the spectacular successes of astroparticle phys- tion of astroparticle experiments using direct and indirect ics in the last 25 years have been the opening of two new detection methods, the well-motivated SUSY-WIMP dark windows to the universe: the neutrino window (the Sun matter hypothesis will be proven or disproven within the and a supernova) and the window of high-energy gamma next 5-10 years. The highly significant annual modulation rays. The study of cosmic neutrinos also revealed that signal observed by DAMA/LIBRA, and its interpretation in neutrinos have mass, with fundamental consequences for terms of dark matter interactions, will also be scrutinized the role of these particles in cosmic evolution. Astrono- in the next few years. The dramatic progress of the liquid- mers and physicists have discovered that the expansion xenon technology over the past 2-3 years demonstrates a of the Universe accelerates (2011 Nobel prize for phys- high momentum, which must be maintained. The recently ics!). Other branches of astroparticle physics have great- approved XENON1T at Gran Sasso laboratory is expected ly improved the levels of sensitivity, something which to start operation in 2014/15. The bolometric experiments makes analogous groundbreaking discoveries in the near CDMS and Edelweiss have recently provided upper limits future likely. This applies to the detection of gravitational close to those of XENON100 and move towards a closer waves and dark matter particles, the study of the origin of US-Europe coordination. We recommend supporting the high energy cosmic rays and neutrinos, the determination development of EURECA, which envisages one ton of of the neutrino mass or, later, the observation of proton sensitive mass, eventually in a common US-Europe frame- decay and the understanding of dark energy. Compared work. Looking beyond the scale of one ton, we strongly to the last version of the ASPERA roadmap in 2008, we recommend that DARWIN, a program aiming to extend witness today a remarkable progress on many fronts, as the target mass of noble liquids to several tons, is pursued well as an increased coordination and networking on a and supported. global scale. Neutrino properties Research priorities differ from country to country, depend- Several highly important experiments in Europe are ing for example on their local infrastructures, or on their either in the commissioning phase or in the final years traditions and historically grown strengths in particular of construction: GERDA, CUORE and the demonstrator fields. The Scientific Advisory Committee (SAC) ranked for SuperNEMO will search for neutrino-less double beta scientific arguments highest but at the same time kept decay, KATRIN for neutrino mass via single beta decay. in mind that there are also historical and political aspects Double CHOOZ, a nuclear reactor experiment, is studying to be considered. We decided to classify our recommen- neutrino oscillations. The mentioned experiments build dations into two categories: a) medium scale projects or on a long experience and validation with precursors. They medium scale upgrades being at different stages of reali- have been recently joined by NEXT, a new approach to zation (investment funds in the category of tens of M€) the search for double beta decay. We renew our strong and b) large scale projects whose construction needs to support for these experiments and look forward to first start towards the middle of the current decade (invest- results. Beyond this, we recommend a phased experi- ment funds on the scale of hundreds of M€). mental approach in neutrino-less double beta decay with In the first category there are a few projects whose fund- a sensitivity (ton scale masses) that will allow to explore ing has to be kept at substantial levels, be it because they fully the mass range predicted by oscillation experi- have an impressive momentum that needs to be main- ments for the inverted mass hierarchy. The underground tained, because they enter a phase with high discovery science program on dark matter and neutrino properties potential, because they go hand in hand with LHC phys- calls for more underground space. In this context, there ics, because they are technologically ready and have a is a unique window of opportunity to extend the present worldwide community behind them, or finally, because Underground Laboratory of Modane (LSM) by taking a delay of crucial decisions and funding could even jeop- advantage of the excavation of the safety tunnel of the ardize the project. In this spirit, we recommend the follow- Frejus road tunnel, which has already started. The new ing projects and urge the agencies to join their forces in laboratory of 60.000 m3 at a great depth could host sever- order to provide effective and substantial support: al of the proposed large new projects. We recommend the timely support for the LSM extension. tor and reactor programs and in particular on whether The large-scale infrastructures whose construction the missing neutrino-mixing parameters are in the range needs to start towards the middle of the current decade that would permit a series of very exciting new measure- include three high-energy projects and one on low-ener- ments (neutrino mass hierarchy, CP violation etc). If the gy neutrino astrophysics: current indications for a large mixing angle θ13 were to be confirmed within one or two years, attractive scenarios TeV gamma-ray astrophysics for the medium-term CERN strategy open up, LAGUNA is The Cherenkov Telescope Array (CTA) is the worldwide therefore clearly at the interface with the CERN Europe- priority project of this field. It combines proven techno- an Strategy Update to be delivered by the end of 2012. logical feasibility with a high speed towards prototyp- As such the LAGUNA project constitutes a high astro- ing, with a guaranteed scientific perspective and a mode particle physics priority to be discussed within the CERN of operation and wealth of data similar to mainstream strategy update process. The presently conceived start astronomy. The cost scale of CTA is 200 M€. We recom- of construction of KM3NeT, the ground based cosmic ray mend the design and the prototyping of CTA, the selec- observatory and a low-energy neutrino detector is in the tion of the site(s), and to proceed vigorously towards start years 2014-2016. We would support a strategy to search of construction in late 2013. for funding opportunities for these projects – both in Europe and worldwide – and promote any one of these High energy neutrinos projects as soon as a corresponding window appears. In the high-energy neutrino domain, the requirements on Astroparticle physicists play a major role in many inter- the necessary sensitivity have tightened, but the scientific national dark energy programs, as e.g. the dominantly case for a large neutrino detector in the Northern hemi- US-funded observatory (first light ca. 2020) or the ESA sphere remains high. The KM3NeT collaboration is work- satellite EUCLID (launch 2019). The committee recom- ing towards a technical proposal for a neutrino telescope mends a strong support for these participations. The path with a substantially larger sensitivity than IceCube. The for research in gravitational waves beyond the advanced expected cost scale is 250 M€ and based on pioneering detectors foresees two very large-scale projects (costs technical work by the European astroparticle community, on the billion Euro scale): the Earth-bound Einstein Tele- also provides access to deep-sea research. scope (E.T.) and the space-bound LISA project. In today’s perspective, E.T. construction would start at the end of High energy cosmic rays the decade and after the first detection of gravitational The cosmic-ray community including the Pierre Auger waves with the advanced detectors. We also look forward collaboration is working towards a next-generation to the results of LISA-Pathfinder. We renew our strong ground-based observatory. These efforts include the support of the LISA mission and preparatory work on E.T. development of new detection technologies, the search We finally emphasize the importance of three transversal for appropriate sites, and the attraction of new partners. aspects: We reiterate the definition of a substantially enlarged ground-based observatory as the priority project of high- Theoretical research is an integral part of astroparticle energy cosmic ray physics.