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Description: The OPERA neutrino experiment is designed to perform the first observation of neutrino oscillations in direct appearance mode in the ν μ → ν τ channel, via the detection of the τ-leptons created in charged current ν τ interactions. The detector, located in the underground Gran Sasso Laboratory, consists of an emulsion/lead target with an average mass of about 1.2 kt, complemented by electronic detectors. It is exposed to the CERN Neutrinos to Gran Sasso beam, with a baseline of 730 km and a mean energy of 17 GeV. The observation of the first ν τ candidate event and the analysis of the 2008-2009 neutrino sample have been reported in previous publications. This work describes substantial improvements in the analysis and in the evaluation of the detection efficiencies and backgrounds using new simulation tools. The analysis is extended to a sub-sample of 2010 and 2011 data, resulting from an electronic detector-based pre-selection, in which an additional ν τ candidate has been observed. The significance of the two events in terms of a ν μ → ν τ oscillation signal is of 2.40σ.

Print ISSN: 1126-6708

Electronic ISSN: 1029-8479

Topics: Physics

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Search for ν μ → ν e oscillations with the OPERA experiment in the CNGS beam (2013)

, ; Agafonova, N. ; Aleksandrov, A. ; [et al.]

Springer

In: Journal of High Energy Physics. 2013; 2013(7): 4. Published 2013 Jul 01. doi: 10.1007/jhep07(2013)004.

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Publication Date: 2013-07-01

Description: A first result of the search for ν μ → ν e oscillations in the OPERA experiment, located at the Gran Sasso Underground Laboratory, is presented. The experiment looked for the appearance of ν e in the CNGS neutrino beam using the data collected in 2008 and 2009. Data are compatible with the non-oscillation hypothesis in the three-flavour mixing model. A further analysis of the same data constrains the non-standard oscillation parameters θ new and $ varDelta m_{mathrm{new}}^2 $ suggested by the LSND and MiniBooNE experiments. For large $ varDelta m_{mathrm{new}}^2 $ values (〉0.1 eV2), the OPERA 90% C.L. upper limit on sin2(2θ new) based on a Bayesian statistical method reaches the value 7.2 × 10−3.

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Topics: Physics

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Final results of the search for νμ → νe oscillations with the OPERA detector in the CNGS beam (2018)

, ; Agafonova, N. ; Aleksandrov, A. ; [et al.]

Springer

In: Journal of High Energy Physics. 2018; 2018(6): 151. Published 2018 Jun 01. doi: 10.1007/jhep06(2018)151.

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Publication Date: 2018-06-01

Description: The OPERA experiment has discovered the tau neutrino appearance in the CNGS muon neutrino beam, in agreement with the 3 neutrino flavour oscillation hypothesis. The OPERA neutrino interaction target, made of Emulsion Cloud Chambers, was particularly efficient in the reconstruction of electromagnetic showers. Moreover, thanks to the very high granularity of the emulsion films, showers induced by electrons can be distinguished from those induced by π 0s, thus allowing the detection of charged current interactions of electron neutrinos. In this paper the results of the search for electron neutrino events using the full dataset are reported. An improved method for the electron neutrino energy estimation is exploited. Data are compatible with the 3 neutrino flavour mixing model expectations and are used to set limits on the oscillation parameters of the 3+1 neutrino mixing model, in which an additional mass eigenstate m 4 is introduced. At high Δm 41 2 (≳0.1 eV2), an upper limit on sin2 2θ μe is set to 0.021 at 90% C.L. and Δm 41 2 ≳ 4 × 10− 3 eV2 is excluded for maximal mixing in appearance mode.

Print ISSN: 1126-6708

Electronic ISSN: 1029-8479

Topics: Physics

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