Claudio Montanari: Status of the Icarus Experiment
In 2013 Icarus concluded a successful run with the T600 detector, taking data both with the CNGS neutrino beam and with cosmic rays. It is mainly thanks to the continuing efforts of the collaboration and the support of INFN that the LAr TPC technology has been taken to full maturity. The T600 detector is the largest LAr TPC ever constructed.
A highly sensitive search for muon to electron neutrino oscillation in appearance mode was proposed in 2009; the proposed dual detector experiment allos to separately identify the delta_m^2 and sin^2 2theta by simultaneous observation at different distances of neutrino interaction with appropriate L/E oscillation path lengths to ensure appropriate matching to the delta_m^2 window for expected anomalies.
A similar dual detector was proposed at the FNAL booster beam. A joint ICARUS/MicroBoone effort is taking place to develop a collaborative program with three detectors at different baselines by 2018. A common Conceptual Design Report has been submitted to the FNAL PAC in January 2015. The proposal got level 1 approval.
The T600 is made of two identical modules, with drift length of 1.5m (1ms), a drift velocity of 1.55 mm/microsecond, and a sampling time of 0.4 microsecond, yielding sub-millimeter resolution in drift direction. It is equipped with 4 wire chambers, 2 per module. One of the key features of this technology is the highly purified liquid, in order to ensure a long drift path of ionization electrons without attenuation. New industrial purification methods have been developed to continuously filter and recirculate both in liquid and gas phases. Icarus has thus demonstrated the effectiveness of single phase LAr TPC technique, paving the way to huge detectors that can work with 5-meter long drifts.
The energy reconstruction is performed by charge integration, with excellent accuracy for contained events. For low-energy electrons the energy resolution is of 11%/sqrt(E/MeV)+2%, and for showers it is of 3%/sqrt/(E/GeV). A measurement of dE/dx allows a remarkable electron/photon separation and particle ID. The momentum of non-contained muons is determined via multiple Coulomb scattering, with a relative momentum resolution of 16% in the 0.4-4 GeV range.
A sterile neutrino search at the FNAL booster neutrino beamline can be done with multiple LAr TPCs, solving the sterile neutrino puzzle. This experiment may clarify the LSND/MiniBooNE and Gallex/reactor anomalies by precisely and independently measuring both electron neutrino appearance and muon neutrino disappearance. In the absence of anomalies, the three detector signals should be a closer copy of each other for all experimental signatures.
At shallow depths, many uncorrelated cosmic rays can be detected during 1ms drift window readout. To mitigate this background, all particles entering the detector must be unambiguously identified. This can be achieved by implementing a cosmic ray tagger and precise timing information from internal scintillation light detectors. 1ns accuracy will enable exploiting the bunched structure of the Booster.
In summary, the LAr TPC technology has been shown to be the way to go for the next generation of short baseline accelerator experiments. The Icarus detector is going to be transferred to FNAL before the end of 2016.