The next generation of long-baseline neutrino experiments will try to determine the neutrino mass ordering and measure the CP violating phase in the leptonic sector. The demonstration of the leptonic CP violation will be an important step towards the leptogenesis mechanism as an explanation of the observed baryon asymmetry in the Universe. While the present generation of neutrino experiments, such as T2K and NOvA, will start providing the first hints of the existence of CP violation and some sensitivity to the mass ordering, they will not be able to provide a significant enough measurement.
The long-baseline Deep Underground Neutrino Experiment (DUNE) is a planned dual-site neutrino experiment projected to be in operation in 2026. This experiment will study high-energy neutrinos from a new, high-intensity wide-band neutrino beam (LBNF) generated by a megawatt-class proton accelerator at Fermilab, after propagating over a distance of 1300 km to a far detector located deep underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. The requirement to cleanly reconstruct multi-GeV neutrino interactions dictates the choice of the liquid argon time projection chamber (LAr TPC) technology as the optimal one for DUNE. The far detector will be composed by four large LAr TPC detectors of 10-kt fiducial mass each. DUNE considers both single- and dual-phase LAr TPC designs for the far detectors. The project is completed with a highly-capable near detector placed very close to the beam.
DUNE's 1300 km baseline delivers > 5σ sensitivity to the neutrino mass hierarchy for any value of δ in seven years of data and a significance for CP violation of at least 3σ for 75% of δ-CP values with an exposure of 850 kt MW year, via neutrino oscillation measurements. The combination of a massive fine-grained detector and underground detector placement also allows DUNE to have broad discovery potential beyond the accelerator neutrino program. The observation of nucleon decay would be a watershed event for the understanding of physics at high energy scales. Neutrinos from supernovae would provide key insights into the physics of gravitational collapse and may also reveal fundamental properties of the neutrino.
CIEMAT contributions to DUNE
The strategy for the far detector construction is built around the formation of international groups (consortia) of institutions responsible for specific aspects of the far detector sub-systems. The CIEMAT group is currently involved in DUNE as members of two consortia: the Dual-Phase Photon Detection (DPPD) System, being the leaders of this consortium (I. Gil), and the Slow Control and Cryogenic Instrumentation Consortium. Members of the CIEMAT group play also an important role in the DPPD Consortium as responsible for the Photosensors (A. Verdugo) and Light Calibration (C. Cuesta) working groups.
DUNE is committed to produce a Technical Design Report of the Far Detectors in 2019. As a previous step, a Techinal Proposal was prepared in 2018. C. Cuesta and C. Palomares were editors of the Dual-Phase Photon Detection System and Slow Control and Cryogenic Instrumentation chapters, respectively.
Simulation work is on-going to optimize the final design of the Dual-Phase Photon Detector System according to the physics requirements. The dual-phase technology, different geometries, and a realistic model of the photon detector timing distributions are being introduced in the optical simulations. Simulation studies on the supernova trigger and the nucleon decay serches based on the light detection system are being developed for the dual phase far detector.
In addition, CIEMAT (I. Gil) is a member of the Technical Board of the DUNE experiment and co-convenor of the DUNE Supernova and Low Energy Neutrino Physics Working Group since 2015.