*CO = Coordinator
CR = Contractor

Which programs will be coordinated?
It is generally difficult to give a closed definition of the scientific content of an interdisciplinary domain as Astroparticle Physics. Nevertheless, six major questions could summarize the content of the domain; they are the following:
1. What is the Universe made of?
2. Do protons have a finite life-time?
3. What are the properties of neutrinos? What is their role in cosmic evolution?
4. What do neutrinos tell us about the interior of Sun and Earth, and about Supernova explosions?
5. What is the origin of cosmic rays? What is the view of the sky at extreme energies?
6. What is the nature of gravity? Can we detect gravitational waves? What will they tell us about violent cosmic processes?

In the following, we attempt a preliminary description of the national programs, addressing these questions. ASPERA will review the funding mechanisms, put in a roadmap perspective, link these projects and eventually merge some of them in future large infrastructure projects. The agencies participating in ASPERA fund over 95% of these programs and employ or support over 90% of the researchers participating in them. There are, preliminarily, 7 large areas of astroparticle and 10 scientific convergence goals that will be pursued inside this ERANET:

4.1.Neutrinos and neutrino astronomy

A series of violent phenomena in the Universe emit high-energy (multi-GeV) neutrinos. The detection of high energy neutrinos would give important clues for the origin of cosmic rays, a centennial puzzle still unsolved, or could reveal the presence of dark matter. An ambitious program of sub-marine or sub-ice neutrino telescopes for their detection is in progress. Different sub-marine neutrino telescope projects are in advanced prototyping stage in the Mediterranean (ANTARES near Toulon, NEMO in Sicily and NESTOR in the Peloponnese).

I. A km3 scale detector would be needed to effectively start neutrino astronomy. A km3 submarine detector in the Mediterranean is complementary (coverage of the full sky) and has advantages (looking towards the very active galactic centre) with respect to an equivalent detector in the Antarctic (ICE-CUBE).
Other experiments, seeking to understand neutrinos, further involve the study of natural radioactivity, specifically the process known as beta-decay. The most sensitive limit comes from the Heidelberg-Moscow Germanium experiment in Gran Sasso. Improvements are expected from the currently running NEMO at Fréjus and CUORICINO-CUORE in Gran Sasso.

II. The next generation of “double-beta decay” experiments will need to use detectors of one ton mass scale of natural radioactivity material, reduce the backgrounds and increase the sensitivity by at least an order of magnitude.
A neutrino accelerator program to test the neutrino properties is in progress both in the US and Europe (CERN to Gran Sasso). A solar neutrino program is also in progress with BOREXINO in Gran Sasso. Historically the experiments that searched for proton decay played a leading role in the discovery of neutrino mass and also in the birth of the domain of astroparticle physics through the discovery of the Supenova 1987a neutrino signals. In the future:

III. A new generation of neutrino supernova and proton decay observatories, from one hundred thousand tons to a megaton, needs European coordination.

4.2.Gravitational waves

Einstein predicted the existence of gravitational waves in his theory of general relativity, but they have not yet been detected. The search for them has been conducted up to now mainly by resonant bar detectors operated at cryogenic temperatures. While the bars are continuously improving their sensitivity the interferometer detectors have recently entered in operation. In Europe the Franco-Italian VIRGO detector, operated by the consortium EGO near Pisa, is in the commissioning phase and the German-UK detector GEO 600, near Hanover has already started to collect scientific data. A completely new antenna in Europe on the horizon of 2010-2015 is under discussion. A tenfold increase in sensitivity increases the possibility of detection by a factor 1000, since this last goes as the volume of the sensitivity reach. Finally, ESA and NASA are planning to fly around 2013 in a shared effort, LISA a 5 million km arm length interferometer to detect gravitational waves at very low frequencies and study in detail gravitational wave signals.

IV. ASPERA will define the European roadmap of upgrades needed by present antennas for the detection of gravitational waves; a detection that could be among the most impressive discoveries of this century. The integration of this program in a world context will be also studied. The complementarity of the ground base program with the ambitious ESA/NASA space program of LISA will be evaluated and accompanied by the proper measures.

4.3.Dark matter and dark energy

Astronomical and cosmological observations indicate that standard (“baryonic”) matter forms only 5% of the matter-energy density of the Universe. There are strong experimental indications that the remaining density consists of some form of non-baryonic non- luminous matter, called "dark matter", which contributes to 25% of the total, while the so-called "dark energy" that accelerates the expansion of the Universe contributes the other 70%.
Searches for the direct detection of dark matter are taking place in a variety of sophisticated experiments using cryogenic detectors or noble gases as targets and detectors, sheltered from cosmic radiation in underground laboratories across Europe. Examples of these are liquid xenon scintillation and ionisation targets (ZEPLIN, XENON, WARP), Germanium or Sodium Iodide detectors (CRESST, EDELWEISS, HDMS, NAIAD, DAMA/LIBRA, IGEX,ROSEBUD, ANAIS, HMDS) in the Gran Sasso (Italy), Fréjus (France) and Camfranc (Spain) tunnel laboratories or the Boulby Mine (UK). Furthermore, another dark matter candidate: “the axion” is actively searched by the CAST experiment at CERN. Indirect searches for dark matter decay products will be performed on ground (neutrino and gamma ray telescopes) and in space (GLAST, Agile, Pamela, AMS-02).

V. The ultimate goal for direct detection dark matter experiments is a ton of bolometric material, exhibiting hopefully a double signature of the interesting events, operating at background levels of the order of 1 background event per ton and per year.
The “dark energy component” will be addressed by systematic searches using both earth based and satellite-borne telescopes, aiming at a high statistics determination of the high redshift Type Ia supernovae distribution, gravitational lensing effects, “baryon oscillation wiggles” and other cosmological effects. These studies are at the border between astroparticle physics and more cosmologically oriented studies. In the context of this ERANET an inter-prioritisation of the studies will be done in collaboration with the astrophysics ERANET (ASTRONET) .

VI. An inter-prioritisation, between the “dark energy” studies and other astroparticle projects will be addressed in view of a coherent European view on the subject.

4.4.High energy gamma-rays

The study of high-energy gamma rays is currently the most promising approach in the search for the origin of cosmic rays. Europe is among the leaders of the field. Based on the experience of the pioneering experiments a new generation of high energy gamma ray telescopes entered or is entering in operation. Among them HESS in Namibia and MAGIC in the Canaries are European lead, and point to complementary parts of the sky. VERITAS and CANGAROO are US and Japan lead respectively. The ARGO Observatory in Tibet is the fruit of collaboration between INFN and several Chinese research centers for the study of cosmic gamma ray sources.
The ground telescopes are complemented by a series of satellite experiments such as the Italian led AGILE (2006) and the US lead, though with strong European participation, GLAST (2007) and AMS02 (2009). The complementarity between space and ground observatories will be exploited in the years to come. The new generation of ground telescopes striving to lower the detection threshold is under study.

VII. The complementarity of the north and south European telescopes, the modes of transnational access turning them to general observatories, their complementarity to space observations and the next generation telescopes will be studied and their implementation prepared.

4.5. Cosmic rays

Over the past three decades, enormously energetic but rare cosmic rays have been detected. The energies of these events are a billion times greater than the highest energies of particles that can be produced at accelerators on Earth. As these extremely energetic cosmic rays are very rare, our understanding of the sources producing them and the way they manage to reach detectors on Earth un-attenuated by the cosmological microwave background radiation is incomplete. The experiment AUGER in the Argentinian pampa is currently dominating the field and many European countries play a leading role in its deployment. In the immediately lower energies, a series of structures in the cosmic ray spectrum (“knee”, ankle”, etc) are suspected to indicate transitions from cosmic rays of galactic and extragalactic origin. The experiment KASKADE in Kalsruhe and EMMA in Pyhasalmi/Finland are studying this domain.Understanding the propagation of cosmic rays in the galaxy requires precise measurements of the fluxes and composition of many nuclei. This will be provided by the forthcoming space experiments Pamela, CREAM and AMS-02 (on the ISS).

VIII. The answer of AUGER, concerning the puzzle of the very high-energy cosmic rays is expected by mid-2007. Independently of the type of the answer (new physics or astronomy using very high energy particles) the after-AUGER, is in discussion. Complementing the south observatory with a northern one, or a satellite experiment looking down the earth atmosphere is an important infrastructure issue.

4.6.Search for antimatter and other exotic states of matter

The absence of primordial antimatter in the cosmos is a puzzle in our current understanding of the structure of the Universe. It is very likely that the early Universe had matter-antimatter equality, so where is antimatter? Searching for nuclear antimatter in space is done either directly by studying the cosmic ray composition or indirectly by measuring the energy spectrum of the diffuse gamma rays flux. This search is better performed using space detectors, since antimatter cosmic rays quickly annihilate in the atmosphere. During the next five years, two space-borne magnetic spectrometers (Pamela launched in 2006 and AMS-02) will increase by three orders of magnitude the current sensitivity to nuclear antimatter.
The European led satellite INTEGRAL, by detecting nuclear gamma ray excitations is producing a mine of information on nuclear astrophysics processes, greatly increasing the topicality of the field. New very sensitive MeV gamma ray space-born detectors are in preparation. Here again coordination with the neighboring ASTRONET is needed.

IX. The search for antimatter and nuclear gamma ray excitations in space will be supported and coordinated in view of coherent presentations in the programs of ESA and NASA.

4.7.Gamma ray bursts, X-Rays etc.

The multi-wavelength study of gamma-ray bursts, energetic X-rays from tens to a hundred of KeV and other studies of the same sort are at the frontier between astroparticle physics and astrophysics studies proper. Sometimes the same instruments address both astrophysics and astroparticle problems. A coordination with astrophysicists organized in parallel structures (ASTRONET) will help the overall coordination of the field.

X. The contact with the neighboring discipline of astrophysics concerning stellar objects and messengers will be improved, and the equivalent priorities will be taken into account in the astroparticle physics roadmap.

4.8.Theory