At the end of the 2011 run, the CERN CNGS neutrino beam has been briefly operated in lower intensity mode with similar to 10(12) p.o.t/pulse and with a proton beam structure made of four LHC-like extractions, each with a narrow width of similar to 3 ns, separated by 524 ns. This very tightly bunched beam allowed a very accurate time-of-flight measurement of neutrinos from CERN to LNGS on an event-by-event basis. The ICARUS T600 detector (CNGS2) has collected 7 beam-associated events, consistent with the CNGS collected neutrino flux of 2.2 x 10(16) p.o.t. and in agreement with the well-known characteristics of neutrino events in the LAr-TPC. The time of flight difference between the speed of light and the arriving neutrino LAr-TPC events has been analysed. The result delta t = 0.3 +/- 4.9(stat.) +/- 9.0(syst.) ns is compatible with the simultaneous arrival of all events with speed equal to that of light. This is in a striking difference with the reported result of OPERA (OPERA Collaboration, 2011) [1] claiming that high energy neutrinos from CERN arrive at LNGS similar to 60 ns earlier than expected from luminal speed. (C) 2012 Elsevier B.V. All rights reserved
Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the µ decay energy spectrum from a sample of stopping µ events acquired during the test run of the ICARUS T600 detector. This detector allows the spatial reconstruction of the events with fine granularity, hence, the precise measurement of the range and dE/dx of the µ with high sampling rate. This information is used to compute the calibration factors needed for the full calorimetric reconstruction of the events. The Michel ρ parameter is then measured by comparison of the experimental and Monte Carlo simulated µ decay spectra, obtaining ρ = 0.72 ± 0.06 (stat.) ± 0.08 (syst.). The energy resolution for electrons below ∼ 50 MeV is finally extracted from the simulated sample, obtaining (E e meas − E e MC )/E e M C = 11%/ E [MeV] ⊕ 2%.
The ICARUS collaboration has demonstrated, following the operation of a 600 ton (T600) detector at shallow depth, that the technique based on liquid Argon TPCs is now mature. The study of rare events, not contemplated in the Standard Model, can greatly benefit from the use of this kind of detectors. In particular, a deeper understanding of atmospheric neutrino properties will be obtained thanks to the unprecedented quality of the data ICARUS provides. However if we concentrate on the T600 performance, most of the ν µ charged current sample will be partially contained, due to the reduced dimensions of the detector. In this article, we address the problem of how well we can determine the kinematics of events having partially contained tracks. The analysis of a large sample of atmospheric muons collected during the T600 test run demonstrate that, in case the recorded track is at least one meter long, the muon momentum can be reconstructed by an algorithm that measures the Multiple Coulomb Scattering along the particle's path. Moreover, we show that momentum resolution can be improved by a factor two using an algorithm based on the Kalman Filtering technique.
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