ICARUS project. A 3000ton detector for neutrino and matter stability searches

The ICARUS Collaboration has developed, in a long duration and stepwise R&D programme, the Liquid Argon Time Projection Chamber (LAr TPC) technology. Current state of the art is represented by a 600 ton detector (T600), that was built using fully industrial methods in about 5 years from 1997 to 2001. During 2001 the detector has been activated and fully tested in a 3-month run, taking cosmic rays data in the assembly hall located in Pavia (Italy). The quality of the recorded data, subsequently analyzed during 2002, demonstrates that the detector performances are consistent with those of laboratory sized prototypes. Next step of the programme is the installation of the T600 in the INFN Gran Sasso Underground Laboratory where it will start to accumulate data and sensitivity for atmospheric neutrinos and proton decay studies. At the same time, by replicating the actual T600 module, we plan to progressively extend the sensitive mass. Taking advantage of the industrial serialization and of the tools already realized for the T600 construction, we will be able to achieve, by the end of 2006, an LAr sensitive mass of about 3000 ton, also complemented by a dedicated magnetized nation spectrometer. The main chapter of the physics programme is a comprehensive study of neutrino oscillations. The contemporaneous observation of both atmospheric neutrinos and neutrinos from the CNGS Long Baseline beam (and possibly also solar and supernovae neutrinos), coupled with the capability to separate with high efficiency the various flavors and interaction channels allows a detailed analysis of several elements of the mixing matrix. In particular, statistically significant v(tau) appearance will be performed down to Deltam(2) greater than or equal to 1.5 x 10(-3) eV(2), and non zero theta(13) will be tested with a sensitivity five times better than the current CHOOZ limit. Also, thanks to the Superior imaging and calorimetric capabilities of the LAr TPC, we will be able to test the nucleon stability in a variety of possible decay channels with sensitivities, despite the limited active mass, largely exceeding those of Superkamiokande.