The observations of gamma-ray telescopes in the last decade changed radically our perception of the Universe and raised new puzzles on the mechanisms powering the most energetic phenomena: gamma-ray bursts and relativistic outflows such as jets from black hole accretion disks or pulsar winds. High-intensity flares with an energy spectrum extending beyond the GeV have been observed. This phenomenon was not foreseen by the laboriously built models and its experimental study has just begun. The next step will be led by instruments able to survey continuously large portions of the sky, and sensitive to the energy gap between satellites and ground arrays (50 GeV — 0.5 TeV).

Present and planned large field-of-view (FoV) gammaray observatories are installed in the Northern Hemisphere, missing in particular the galactic center. While a wide FoV Southern Hemisphere observatory will surely be proposed and built, the question is whether it will be similar to the existing extensive air shower (EAS) arrays, or an innovative solution able to cover the energy gap between satellites and ground in wide FoV observations. The technological challenges of lowering the energy threshold of air shower arrays have been considered nearly impossible to overcome, as they stem directly from the physics of air showers. The goal of LATTES is to design, prototype and construct a a ground array able to monitor the Southern gammaray sky above 50 GeV, bringing to ground the wide fieldof-view and large duty cycle observations characteristic of satellites, with comparable sensitivity and a cost one order of magnitude lower. Such an instrument will be a powerful time-variance explorer, able to issue pointing alerts to IACTs (Imaging Atmospheric Cherenkov Telescopes), boosting the efficiency of these powerful instruments, and thus fully complementary to CTA. It will collect abundant and highly relevant data and play a fundamental role in the search for emissions from extended regions, as the Fermi bubbles or dark matter annihilation regions.

To overcome the huge technology issues involved, LATTES proposes an innovative concept: a compact EAS array of hybrid detector units, covering an area of at least 20,000 m2, to be placed at high altitude (about 5,000 m above sea level, a.s.l.) in the Southern hemisphere. Each detector unit combines two autonomous RPCs (Resistive Plate Chambers), with good space and time resolution) with a WCD (Water Cerenkov Detector), ensuring trigger efficiency and efficient background rejection, and thus good sensitivity all the way down to 50 GeV.

The proposed solution is conceptually and technologically innovative but relies on wellgrounded R&D in which LIP had a leading role. In fact, the detector concept was originally developed at LIP and the LIP-Coimbra team members have a recognized world-leader expertise in RPCs. The LATTES concept has been proposed during 2016 by scientists from Portugal (LIP), Brazil (CBPF) and Italy (INFN-Padova and Roma). Scientists from other countries, namely from Spain and Check Republic, have attended the LATTES meetings in 2016 as observers. To pursue such an ambitious goal, a sound international collaboration has to be formed. The collaboration is taking form and should get the first dedicated fundings during 2017.

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Responsável de Grupo:  

Mário Pimenta