A new, very massive modular Liquid Argon Imaging Chamber to detect low energy off-axis neutrinos from the CNGS beam (Project MODULAr)

Abstract

The paper is considering an opportunity for the CERN/GranSasso (CNGS) neutrino complex, concurrent time-wise with T2K and NOvA projects, with the aim of improving the sensitivity on ν μ ↔ ν e θ 13 mixing angle by nearly an order of magnitude with respect to T2K expectations. The experiment is based on a ≈20 kt fiducial volume LAr-TPC, following very closely the technology developed for the ICARUS-T600. The present preliminary proposal, called MODULAr, is focused on the following three main activities, for which we seek an extended international collaboration: (1) The neutrino beam from the CERN 400 GeV proton beam and an optimized horn focussing, eventually with an increased intensity in the framework of the LHC accelerator improvement programme. (2) A new experimental area LNGS-B, of at least 50,000 m 3 at 10 km off-axis from the main laboratory, eventually upgradable to larger sizes. A location is under consideration at about 1.2 km equivalent water depth. The bubble chamber like imaging and the very fine calorimetry of the LAr-TPC detector will ensure the best background recognition not only from the off-axis neutrinos from the CNGS but also for proton decay and cosmic neutrinos. (3) A new LAr Imaging detector, at least initially with about 20 kt fiducial mass, realised with a modular set of four identical, but independent units, each of about 5 kt, “cloning” the basic technology of the T600. Further phases may foresee extensions of MODULAr to a mass required by the future physics goals. Compared with large water Cherenkov (T2K) and fine grained scintillators (NOvA), the LAr-TPC offers a higher detection efficiency for a given mass and lower backgrounds, since virtually all channels may be unambiguously recognized. In addition to the search for θ 13 oscillations and CP violation, it would be possible to collect a large number of accurately identified cosmic ray neutrino events and perform search for proton decay in the exotic channels.