Abstract
The OPERA experiment was designed to discover the vτ appearance in a vμ beam, due to neutrino oscillations. The detector, located in the underground Gran Sasso Laboratory, consisted of a nuclear photographic emulsion/lead target with a mass of about 1.25 kt, complemented by electronic detectors. It was exposed from 2008 to 2012 to the CNGS beam: an almost pure vμ beam with a baseline of 730 km, collecting a total of 1.8·1020 protons on target. The OPERA Collaboration eventually assessed the discovery of vμ→vτ oscillations with a statistical significance of 6.1 σ by observing ten vτ CC interaction candidates. These events have been published on the Open Data Portal at CERN. This paper provides a detailed description of the vτ data sample to make it usable by the whole community.
Highlights
Background & SummaryNeutrino oscillations are a quantum mechanical phenomenon whereby a neutrino created with a specific flavour can be measured to have a different flavour as it propagates through space
Neutrino oscillations with three flavours including CP (Charge, parity) and CPT (Charge, parity, and time reversal symmetry) violations were discussed by Pontecorvo and Bilenky, after the discovery of the τ lepton in 19753,4
The mixing of the three neutrino flavours into mass eigenstates can be described by the 3 × 3 Pontecorvo-Maki-NakagawaSakata matrix[1] with three mixing angles and a CP-violating phase. Several experiments, such as Kamiokande[5], MACRO6 and Soudan-27, reported hints of the so-called “atmospheric neutrinos problem”: a deficit in the measured flux of vμ produced by cosmic ray interactions in the high atmosphere as compared to expectations
Summary
Neutrino oscillations are a quantum mechanical phenomenon whereby a neutrino created with a specific flavour can be measured to have a different flavour as it propagates through space. The mixing of the three neutrino flavours into mass eigenstates can be described by the 3 × 3 Pontecorvo-Maki-NakagawaSakata matrix[1] with three mixing angles and a CP-violating phase Several experiments, such as Kamiokande[5], MACRO6 and Soudan-27, reported hints of the so-called “atmospheric neutrinos problem”: a deficit in the measured flux of vμ produced by cosmic ray interactions in the high atmosphere as compared to expectations. To definitely confirm the three-flavour neutrino oscillation mechanism, the observation of vτ appearance resulting from vμ → vτ transitions in a vμ beam was required. Since the expected background was (0.25 ± 0.05) events, the five candidates have a combined significance of 5.1 σ16, providing a direct and definite proof of the oscillation mechanism underlying the observation of vμ disappearance. The Usage Notes describes possible ways to use the dataset
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