A
bstract
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 2.40
σ
.
The OPERA experiment Agafonova, N.; Aleksandrov, A.; Aoki, S. ...
Nuclear and particle physics proceedings,
10/2015, Letnik:
267-269
Journal Article
Recenzirano
Odprti dostop
The OPERA experiment was designed to study νμ→ντ oscillations in appearance mode using the CERN to Gran Sasso high energy neutrino beam. From 2008 to 2012, 19505 CNGS neutrino interactions were ...recorded in the OPERA detector. At the present status of the analysis, 4 ντ candidate events have been observed, establishing the oscillation mechanism in the atmospheric sector with a significance of 4.2 σ. The oscillation analysis will be presented in detail and the candidate events will be described. The final measurement of the atmospheric muon charge ratio in the TeV region will be also reported.
A bstract 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 eV 2 ), the OPERA 90% C.L. upper limit on sin 2 (2 θ new ) based on a Bayesian statistical method reaches the value 7 . 2 × 10 −3 .
The OPERA experiment was designed to observe ν μ → ν τ oscillations through τ appearance on the CERN Neutrino to Gran Sasso (CNGS) beam over a baseline of 730 km. OPERA was a hybrid experiment ...composed of lead plates and emulsion layers acting as a target for neutrino interactions. The experiment was complemented with electronic detectors: scintillator strips used as Target Trackers and muon spectrometers. A review of the OPERA final results is presented in this paper.
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 π0s, 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 m4 is introduced. At high Δm412 (≳0.1 eV2), an upper limit on sin2 2θμe is set to 0.021 at 90% C.L. and Δm412 ≳ 4 × 10− 3 eV2 is excluded for maximal mixing in appearance mode.
The OPERA experiment is searching for nu_mu -> nu_tau oscillations in appearance mode i.e. via the direct detection of tau leptons in nu_tau charged current interactions. The evidence of nu_mu -> ...nu_tau appearance has been previously reported with three nu_tau candidate events using a sub-sample of data from the 2008-2012 runs. We report here a fourth nu_tau candidate event, with the tau decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analysed events and the low background, nu_mu -> nu_tau oscillations are established with a significance of 4.2sigma.
The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the ...$\nu_\mu\rightarrow\nu_\tau$ channel, the $\nu_\tau$ signature being the identification of the $\tau$-lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. It is placed in the high energy long-baseline CERN to LNGS neutrino beam (CNGS) 730 km away from the neutrino source. The observation of a first $\nu_\tau$ candidate event was reported in 2010. In this paper, we present the status of the experiment based on the analysis of the data taken during the first two years of operation (2008-2009). The statistical significance of the one event observed so far is then assessed.
The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) has been designed to perform the first detection of neutrino oscillations in direct appearance mode through the study of ...the $\nu_\mu\rightarrow\nu_\tau$ channel. The hybrid apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2008 and 2009. After a brief description of the beam, the experimental setup and the procedures used for the analysis of the neutrino events, we describe the topology and kinematics of a first candidate $\nu_\tau$ charged-current event satisfying the kinematical selection criteria. The background calculations and their cross-check are explained in detail and the significance of the event is assessed.
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