Search for the νμ → ντ oscillation with the OPERA hybrid detector

Abstract

This work reviews the status of the international OPERA experiment aimed at searching for the ν μ → ν τ oscillation. Development of the emulsion techniques in the preceding DONUT and CHORUS experi ments is described. A brief overview of the NOMAD experiment is given, in which properties of ν τ interac tions were thoroughly investigated. Characteristics of the CERN-Gran Sasso (CNGS) neutrino beam are given, the structure of the OPERA hybrid detector and the functions of its subsystems are considered, and the automatic emulsion scanning technique is briefly reviewed. Uncertainties in reconstruction of event param eters using the electronic and emulsion detectors are discussed and the procedure adopted in the experiment for identification of ν τ interactions is described. The main sources of background in the search for ν μ → ν τ oscillation are considered. Topologies of the first two ν τ candidates observed in the OPERA emulsion detector are presented. Possibilities of increasing the ν τ interaction selection efficiency using multidimensional criteria are briefly discussed.

Search for anomalies in the ν e appearance from a ν μ beam

“…[6]. Recently a similar search performed at the same CNGS beam by the OPERA experiment has confirmed our finding and the absence of anomalous oscillations with an independent limit sin 2 (2θ new ) < 7.2×10 -3 [19].…”

“…The resulting oscillation probability distribution for neutrino and for E ν > 475 MeV (square red points) appears incompatible with the antineutrino LNSD effect. In the 200 < E ν QE < 475 MeV region (triangular red points) -below the sensitive E ν L region of LSND -the new MiniBooNE effect is widely incompatible with the averaged upper probability limits to anomalies from the present paper and from OPERA [19] in their E ν L regions. An extrapolation from ICARUS (black curves marked as 1, 2 and 3) to larger values of E/L for two-neutrino oscillation parameters simultaneously compatible with LSND, MiniBooNe and Karmen is also shown as guidance.…”

Joint short- and long-baseline constraints on light sterile neutrinos

“…ν e appearance data of the LSND [17], MiniBooNE [30,31], BNL-E776 [32], KAR-MEN [33], NOMAD [34], ICARUS [35] and OPERA [36] experiments. The two last ones have been treated following the approach described in [37].…”