Large Underground Observatory for Proton Decay, Neutrino Astrophysics and CP-violation in the Lepton Sector

 
 

A new research infrastructure supporting deep underground cavities able to host a very large multipurpose next-generation neutrino observatory of a total volume in the range of 100.000 to 1.000.000 m3 will provide new and unique scientific opportunities in the field of particle and astroparticle physics, attracting interest from scientists worldwide to study proton decay and neutrinos from many different natural sources, very likely leading to fundamental discoveries.


The Superkamiokande Water Cerenkov Imaging detector with a total volume of 50.000 m3 and the T2K long baseline neutrino oscillation experiment in Japan represent today the state-of-the-art in this field, addressing neutrino astrophysics and studying neutrino properties. Swiss groups are visibly engaged in the T2K experiment since 2006. First physics results are expected in summer 2010.


One of the main reasons for a new observatory beyond Superkamiokande is to find direct evidence for the Unification of all elementary forces, by searching for a rare process called proton decay. The new underground detector will pursue the only possible path to directly test physics at the GUT scale, significantly extending the proton lifetime search sensitivities up to 1035 years, a range compatible with several theoretical models.


While searching for proton decays, the continuously sensitive underground observatory will offer the opportunity to concurrently detect several other rare phenomena. In particular, it will sense a large number of neutrinos emitted by exploding galactic and extragalactic type-II supernovae, allowing an accurate study of the mechanisms driving the explosion. The neutrino observatory will also allow precision studies of other astrophysical or terrestrial sources like solar and atmospheric ones, and search for new sources of astrophysical neutrinos, like for example the diffuse neutrino background from relic supernovae or those produced in Dark Matter (WIMP) annihilation in the centre of the Sun or the Earth.


In addition, the recent measurements of neutrino oscillations point forward to the need to couple the new neutrino observatory to advanced neutrino beams for instance from CERN, to study matter-antimatter asymmetry in neutrino oscillations, thereby addressing the outstanding puzzle of the origin of the excess of matter over antimatter created in the very early stages of evolution of the Universe.


Europe currently has four world-class national deep underground laboratories with high-level technical expertise, located in Boulby (UK), Canfranc (Spain), Gran Sasso (Italy), and Modane (France), hosting detectors looking for Dark Matter or for neutrino-less double beta decays, or performing long-baseline experiments. However, none of the existing laboratory is large enough for the next-generation experiment contemplated here.


The FP7 Design Study LAGUNA (Large Apparatus studying Grand Unification and Neutrino Astrophysics), initiated and coordinated by ETH Zurich and involving 21 beneficiaries, composed of academic institutions from Denmark, Finland, France, Germany, Poland, Spain, Switzerland, United Kingdom, as well as industrial partners specialized in civil and mechanical engineering and rock mechanics, is assessing the feasibility of this Research Infrastructure in Europe. The LAGUNA consortium is evaluating possible extensions of the existing deep underground laboratories in Europe, and on top considers the creation of new laboratories in the following regions: Caso (Italy), Pyhäsalmi (Finland), Sierozsowice (Poland) and Slanic (Romania).


Similar plans are emerging worldwide, for instance in North America with the Deep Underground Science and Engineering Laboratory (DUSEL) at Homestake (South Dakota), envisioning a deep underground facility coupled to US accelerator laboratories located at appropriate distances, for long baseline neutrino oscillation experiments. In Asia, the Japanese High Energy Research Accelerator Research Organization (KEK) roadmap foresees extensions of the JPARC neutrino programme beyond the current T2K experiment by increasing the neutrino beam intensity and by constructing a new far detector replacing SuperKamiokande. This international landscape underlines the “global” nature of the project, with potential options being considered in several continents, jointly debated by the international scientific community. It is therefore likely that only one such facility will be built worldwide.

 

Welcome to the search for the grand unification and to the observation of the Universe with neutrinos

The proton can spontaneously disintegrate into lighter elementary constituents if the strong, weak and electromagnetic forces become unified at a very high-energy scale (1016 GeV or beyond, at a much higher energy scale than what can be directly probed by the LHC), as predicted by Grand Unified Theories (GUT). Superkamiokande did not so far find proton decay, implying that the proton has a lifetime greater than 1033 years. Precision measurements performed at the CERN LEP collider in the 1990’s do support GUT and further information could come from the LHC.

The Earth