OPERA Experiment Research Articles

Gas mixture studies for streamer operated Resistive Plate Chambers

Resistive Plate Chambers operated in streamer mode are interesting detectors in neutrino and astro-particle physics applications (like OPERA and ARGO experiments). Such experiments are typically characterized by large area apparatuses with no stringent requirements on detector aging and rate capabilities. In this paper, results of cosmic ray tests performed on a RPC prototype using different gas mixtures are presented, the principal aim being the optimization of the TetraFluoroPropene concentration in Argon-based mixtures. The introduction of TetraFluoroPropene, besides its low Global Warming Power, is helpful because it simplifies safety requirements allowing to remove also isobutane from the mixture. Results obtained with mixtures containing SF6, CF4, CO2, N2 and He are also shown, presented both in terms of detectors properties (efficiency, multiple-streamer probability and time resolution) and in terms of streamer characteristics.

Results from the OPERA experiment in the CNGS beam

The OPERA experiment at the Gran Sasso underground laboratory was designed to study νμ → ντ oscillations in appearance mode in the CNGS neutrino beam. In this paper we report the detection of the 5th ντ candidate event found in the analysis of an enlarged data sample. Given the number of analysed events and the low background, νμ → ντ oscillations have been established with a significance of 5.1σ. The analysis of the present electron neutrino sample in the framework of the 3 + 1 sterile model is also presented. Finally the analysis of the muon charge ratio in the cosmic ray sample is discussed.

Search for sterile neutrino mixing in the muon neutrino to tau neutrino appearance channel with the OPERA detector

The OPERA experiment observed νμ → ντ oscillations in the atmospheric sector. To this purpose the hybrid OPERA detector was exposed to the CERN Neutrinos to Gran Sasso beam from 2008 to 2012, at a distance of 730 km from the neutrino source. Charged-current interactions of ντ were searched for through the identification of τ lepton decay topologies. The five observed ντ interactions are consistent with the expected number of events in the standard three neutrino framework. Based on this result, new limits on the mixing parameters of a massive sterile neutrino may be set. Preliminary results of the analysis performed in the 3+1 neutrino framework are here presented.

Latest results on νμ → ντ oscillations from the OPERA experiment

The OPERA experiment is designed to prove neutrino oscillations in the νμ to ντ channel through the direct observation of the tau lepton in tau neutrino charged current interactions. The experiment has accumulated data for five years, from 2008 to 2012, with the CERN Neutrinos to Gran Sasso (CNGS), an almost pure νμ beam.In the last two years, a very large amount of the data accumulated in the nuclear emulsions has been analyzed. The latest results on oscillations with the increased statistics, which include a fourth tau neutrino candidate event, will be presented. Given the extremely low expected background, this result corresponds to the observation of the oscillation process with a four sigma level significance.

Short-lived particle search procedure in the OPERA experiment. Application to charm decays

The OPERA experiment has recently provided evidence of νμ→ντ neutrino oscillations in appearance mode through the detection of tau leptons produced in ντ Charged Current interactions. The OPERA detector collected data from 2008 to 2012, when it was exposed to the CNGS muon neutrino beam from CERN to Gran Sasso, 730 km away from the source. We report on the search procedure for short-lived particles and on its validation with charmed hadron decays. The latter, produced in about 4% of the neutrino interactions in OPERA, are an important background to the νμ→ντ channel and an ideal control sample as their decay exhibits topological and kinematical features strongly resembling the tau's decay.

Measurement of the TeV atmospheric muon charge ratio with the full OPERA data set

The OPERA detector, designed to search for νμ→ντ oscillations in direct appearance mode, is located in the underground Gran Sasso laboratory, a privileged location to study TeV-scale cosmic rays. Given the large rock depth and the detector's wide acceptance, the apparatus was used to measure the atmospheric muon charge ratio in the TeV energy region. The muon charge ratio, defined as the number of positive over negative charged muons, provides an understanding of the mechanism of multiparticle production in the atmosphere in kinematic regions not accessible to accelerators, as well as information on the primary cosmic ray composition. We present the results obtained with the full statistics collected by OPERA from 2008 to 2012. The combination of two data sets with opposite magnet polarities allows minimizing systematic uncertainties and reaching an accurate determination of the muon charge ratio. Relevant parameters on the composition of primary cosmic rays and the associated kaon production in the forward fragmentation region are obtained.

Search for νμ → νe oscillations with the OPERA experiment in the CNGS beam

The OPERA hybrid detector, designed to prove neutrino oscillations in the νμ→ντ channel, was exposed to the CNGS νμ beam at a distance of 730 km from the neutrino source. Profiting of the tracking capabilities of its Emulsion Cloud Chamber system, OPERA can perform also a search for νμ→νe oscillations. Current results are compatible with the non-oscillation hypothesis in the three flavour mixing model. The same data allow to constrain the non-standard oscillation parameters θnew and Δmnew2 indicated by the LSND and MiniBooNE experiments.

Estimating the Baseline between CERN Target and LNGS Reference Points

AbstractThis work is part of the European Organization for Nuclear Research (CERN) Neutrinos to Gran Sasso (CNGS) Project, aimed at estimating the velocity of neutrino beams directed from CERN in Geneva toward the Gran Sasso National Laboratory (LNGS) in Assergi, Italy. In particular, the distance has to be estimated between the Large Volume Detector, Icarus, and Borexino reference points, located inside LNGS, and the CERN laboratory target. All the points at LNGS and CERN are placed in underground laboratories. Traditional surveying methods must then be applied for connecting the reference points to benchmarks established outside the underground laboratories in the open field. In this way, the two local LNGS and CERN geodetic networks can be connected by the Global Navigation Satellite System (GNSS) technique. The CERN target was already estimated with respect to a local GNSS network in the International Terrestrial Reference Frame 97. To estimate the position of LNGS points, a new local GNSS network has...

Search for sterile neutrino mixing in theνμ→ ντappearance channel with the OPERA detector

The OPERA experiment has observed muon neutrino to tau neutrino oscillations in the atmospheric sector in appearance mode. Five ν τ candidate events have been detected, a number consistent with the expectation from the “standard” 3ν framework. Based on this result new limits on the mixing parameters of a massive sterile neutrino have been set. The analysis is performed in the 3+1 neutrino model.

SHiP: a new multipurpose beam-dump experiment at the SPS

SHiP is an experiment to look for very weakly interacting particles at a new to be constructed beam-dump facility at the CERN SPS. The SHiP Technical Proposal has been submitted to the CERN SPS Committee in April 2015. The 400 GeV/c proton beam extracted from the SPS will be dumped on a heavy target with the aim of integrat- ing 2× 10 20 proton on target in five years. A detector located downstream of the targe t, based on a long vacuum tank followed by a spectrometer and particle identifi cation de- tectors, will allow probing a variety of models with light long-lived exotic partic les and masses below a few GeV/c 2 . The main focus will be the physics of the so-called Hid- den Portals, i.e. search for Dark Photons, Light scalars and pseudo-scalars, and Heavy Neutral Leptons (HNL). The sensitivity to HNL will allow for the first time to pr obe, in the mass range between the kaon and the charm meson mass, a coupling range for which Baryogenesis and active neutrino masses could also be explained. Integrated in SHiP is an Emulsion Cloud Chamber, already used in the OPERA experiment, which will allow to study active neutrino cross-sections and angular distributions. In par ticular SHiP can distinguish betweeno? and ¯ o?, and their deep inelastic scattering cross sections will be measured with statistics three orders of magnitude larger than currently available.

Ohm’s Law Refutes Current Version of the Special Theory of Relativity

It is shown that Ohm’s law is not only the main electrical engineering law, but also a generally scientific worldview law of the extreme significance, as in the interpretation of Steinmetz it proves physical reality of imaginary numbers theoretically and experimentally in the most indisputable way. Thus, it refutes the principle of light speed non-exceedance, which is fundamental in the special theory of relativity. Moreover, unlike the MINOS and OPERA experiments recognized by physical com-munity as not enough reliable, which were conducted for the same purpose, alternative experiments were performed during the research of oscillation processes in linear electric circuits. Therefore, they are absolutely reliable and conclusive as can be repeated and verified in any electrical engineering laboratory. The principle of phy-sical reality of imaginary numbers proven by the electrical engineering experiments is generally scientific, since mathematics is the universal language of the exact sciences. Therefore, all scientific theories and hypotheses in quantum mechanics, relativity theory, geo-physics, cosmology, optics, radio electronics and other sciences should be adjusted accordingly, given the principle of physical reality of imaginary numbers. There is an example of how this can be done in the special theory of relativity and astrophysics. This approach allowed explanation of dark matter and dark energy, which correspond to the invisible parallel universes existing in extra dimensions.

The OPERA experiment

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.

Large-Angle Scattering of Multi-GeV Muons on Thin Lead Targets

The probability of large-angle scattering for multi-GeV muons in thin ($t/X_0 \sim 10^{-1}$) lead targets is studied. The new estimates presented here are based both on simulation programs (GEANT4 libraries) and theoretical calculations. In order to validate the results provided by simulation, a comparison is drawn with experimental data from the literature. This study is particularly relevant when applied to muons originating from $\nu_\mu^{CC}$ interactions of CNGS beam neutrinos. In that circumstance the process under study represents the main background for the $\nu_\mu \to \nu_\tau$ search in the $\tau \to \mu$ channel for the OPERA experiment at LNGS. Finally, we also investigate, in the CNGS context, possible contributions from the muon photo-nuclear process which might in principle also produce a large-angle muon scattering signature in the detector.

Discovery of τ Neutrino Appearance in the CNGS Neutrino Beam with the OPERA Experiment.

The OPERA experiment was designed to search for ν_{μ}→ν_{τ} oscillations in appearance mode, i.e., by detecting the τ leptons produced in charged current ν_{τ} interactions. The experiment took data from 2008 to 2012 in the CERN Neutrinos to Gran Sasso beam. The observation of the ν_{μ}→ν_{τ} appearance, achieved with four candidate events in a subsample of the data, was previously reported. In this Letter, a fifth ν_{τ} candidate event, found in an enlarged data sample, is described. Together with a further reduction of the expected background, the candidate events detected so far allow us to assess the discovery of ν_{μ}→ν_{τ} oscillations in appearance mode with a significance larger than 5σ.

Results from the OPERA experiment

The OPERA neutrino experiment was designed to perform a unique appearance measurement in the CNGS beam to confirm the oscillation mechanism in the atmospheric sector. Runs were successfully carried out from 2008 to 2012. The detection of τ leptons produced in ντ CC interactions and of their decays is accomplished exploiting the high spatial resolution of nuclear emulsions. Furthermore OPERA has good capabilities in detecting electron neutrino interactions, setting limits on the νμ→νe oscillation channel. The status of the analysis is reported together with updated results on both oscillation channels.

Results from the OPERA experiment at the CNGS beam

The OPERA experiment at the Gran Sasso underground laboratory is searching for νμ → ντ oscillations in appearance mode in the CNGS neutrino beam. Four ντ candidate events have been found so far, using a sub-sample of data from the 2008-2012 runs. Given the number of analysed events and the low background, νμ → ντ oscillations are established with a significance of 4.2 σ. In this paper the data analysis is discussed, with emphasis on the background constraints obtained using dedicated data-driven control samples. We present also the analysis of the τ neutrino and electron neutrino data in the framework of the 3+1 sterile neutrino model. The measurement of the muon charge ratio in the collected cosmic ray sample is also reported.

Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam

The OPERA experiment, exposed to the CERN to Gran Sasso $\nu_\mu$ beam, collected data from 2008 to 2012. Four oscillated $\nu_\tau$ Charged Current interaction candidates have been detected in appearance mode, which are consistent with $\nu_\mu \to \nu_\tau$ oscillations at the atmospheric $\Delta m^2$ within the "standard" three-neutrino framework. In this paper, the OPERA $\nu_\tau$ appearance results are used to derive limits on the mixing parameters of a massive sterile neutrino.

Retrospective Analysis of the Well-Known Experiments

We analyze ray path in the Sagnac and Michelson-Gale experimental setups and in the Michelson interferometer. Work of rotating interferometers is proved to be in full agreement with the concept of static ether. A theory of Michelsoninterferometer work in vacuum and in a gas is developed. Three second-order small factors pointed out in papers by Demjanov and Shamir-Fox are taken into account. The new results are considerably different from conclusions of the mentioned papers. An absolute laboratory velocity of 10 km/s found by Miller is reevaluated to become 236 km/s according to the new formulas. A new theory of the Michelson interferometer fully agrees with the concept of the static ether. It is predicted that in the well-known OPERA experiment, the diurnal plot of the neutrino velocity should have one maximum and one minimum separated by a time interval of 12 hours.

Recent Results from the OPERA Experiment

The OPERA experiment has been designed to perform the first detection of neutrino oscillations in the νμ → ντ channel in direct appearance mode, through the event by event detection of the tau lepton produced in ντ charged current interactions. OPERA is a hybrid detector, made of emulsion/lead target elements and of electronic detectors, placed in the CNGS muon neutrino beam from CERN to Gran Sasso, 730km away from the source. Neutrino interactions from the CNGS neutrino runs were recorded from 2008 until the end of 2012. We report on the data sample analysed so far and give the latest OPERA results on νμ → ντ and νμ → νe oscillation searches.

Locating the neutrino interaction vertex with the help of electronic detectors in the OPERA experiment

The OPERA experiment is designed for the direct observation of the appearance of ντ from νμ → ντ oscillation in a νμ beam. A description of the procedure of neutrino interaction vertex localization (Brick Finding) by electronic detectors of a hybrid OPERA setup is presented. The procedure includes muon track and hadronic shower axis reconstruction and a determination of the target bricks with the highest probability to contain the vertex.