Pure Νμ Research Articles

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.

T2K: New physics results

The T2K experiment is designed to probe the θ13 neutrino mixing parameter by looking for the appearance of νe in a pure νμ beam and to precisely measure atmospheric Δm2 and θ23 parameters. A neutrino beam produced at J-PARC, Japan, is aimed at 2.5° off-axis angle to the Super-Kamiokande far neutrino detector, 295km away. The narrow energy neutrino beam peaked at about 600 MeV is optimized to maximize the probability of oscillation at the atmospheric Δm2 scale. The neutrino beam is monitored by a complex of neutrino near detectors at 280m from the production target. T2K has successfully operated since January 2010. Data-taking has been presently paused due to the recent earthquake in Japan. Results on measurements of νe appearance and νμ disappearance are reported.

ND280 TPC contribution to recent T2K results

The T2K (Tokai to Kamioka) experiment is a long baseline neutrino oscillation experiment designed to measure the θ13 neutrino mixing parameter by looking for the appearance of νe in an almost pure νμ beam. The concurrent measurement of νμ disappearance allows refined measurements of the atmospheric Δm2 and of the θ23 mixing parameters.A neutrino beam is produced at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai, Japan, and aimed at 2.5° off the direction of the Super-Kamiokande (SK) detector, 295 km away. The resulting narrow energy band neutrino beam at the SK location, peaked at about 600 MeV, is optimized to maximize the probability of oscillation at the atmospheric Δm2 scale, minimizing at the same time the backgrounds for νe searches. The neutrino beam is monitored before the oscillation by a Near Detector, ND280 located at J-PARC at 280 m from the target. A key element of the T2K Near Detector is composed of three large TPCs instrumented with MicroMEGAS detectors used to measure the neutrino spectrum and flavor composition before the oscillation. The charge and momentum of the charged particles crossing the TPCs are reconstructed, as well as the ionization energy loss in the TPCs allowing to distinguish electrons from muons.T2K has successfully operated since January 2010, and it has presently been paused due to the recent earthquake in Japan. Results on the search for νe appearance and of νμ disappearance have been presented in this talk, particularly stressing the inputs to these measurements from the TPCs.

Summary of the OPERA analysis

The OPERA experiment is located in the Gran Sasso underground laboratory and designed to directly detect the appearance of ντ in a pure νμ beam by observing the decay of charged τ leptons produced in ντ charged current interactions. The OPERA detector is a hybrid detector, containing electronic detectors (ED) and high resolution nuclear emulsions. A short introduction to the detector is presented. The analysis procedures will be described, including the analysis flow chain and the vertex decay search procedure. First results will be presented, including the main kinematic measurements obtained until now and the cross checks made on the background expectation.

The Photographic Emulsion Technology of the OPERA Experiment on its Way to Find the [formula omitted] Oscillation

The OPERA experiment (Oscillation Project with Emulsion tRacking Apparatus) is a long baseline appearance search for νμ→ντ oscillation. A pure νμ beam from CERN is sent to the 730 km far away LNGS underground laboratory in Italy where the OPERA detector is located. The charged current ντ interaction will produce a tau lepton which then can be identified according to its decay topology. The detection of the tau requires a high resolution of the active detection material because of the short lifetime of the tau. Nuclear emulsion films are the most suitable detector material capable of fulfilling this requirement. This article is going to review the status of the experiment, the detector and the way to find the νμ→ντ oscillation by observing the tau lepton. Special emphasis is put on the emulsion detection technique.

Neutrinos from CERN to Gran Sasso: The CNGS project

The CNGS project (CERN Neutrinos to Gran Sasso) has been approved to make an unambiguous and direct observation of νμ − ντ oscillations. An intense and relatively pure νμ beam is generated at CERN and directed towards LNGS (Laboratori Nazionali del Gran Sasso) in Italy. Two experiments, OPERA already started in 2007 and ICARUS T600, will try to detect tau neutrinos using large and complex detectors. These "appearance" experiments will use the τ decay topology as signature of the presence of ντ in the initial neutrino beam. An overview of the CNGS beam facility is given. Results from the first observed OPERA events and performances are presented. Few elements are given concerning the ICARUS T600 starting.

The OPERA experiment in the CERN to Gran Sasso neutrino beam

The OPERA neutrino oscillation experiment has been designed to prove the appearance of ντ in a nearly pure νμ beam (CNGS) produced at CERN and detected in the underground Hall C of the Gran Sasso Laboratory, 730 km away from the source. In OPERA, τ leptons resulting from the interaction of ντ are produced in target units called bricks made of nuclear emulsion films interleaved with lead plates. The OPERA target contains 150000 of such bricks, for a total mass of 1.25 kton, arranged into walls interleaved with plastic scintillator strips. The detector is split into two identical supermodules, each supermodule containing a target section followed by a magnetic spectrometer for momentum and charge measurement of penetrating particles. Real time information from the scintillators and the spectrometers provide the identification of the bricks where the neutrino interactions occurred. The candidate bricks are extracted from the walls and, after X-ray marking and an exposure to cosmic rays for alignment, their emulsion films are developed and sent to the emulsion scanning laboratories to perform the accurate scan of the event. In this paper, we review the design and construction of the detector and of its related infrastructures, and report on some technical performances of the various components. The construction of the detector started in 2003 and it was completed in Summer 2008. The experiment is presently in the data taking phase. The whole sequence of operations has proven to be successful, from triggering to brick selection, development, scanning and event analysis.

The OPERA experiment and the first events from the CNGS neutrino beam

The aim of the OPERA experiment is to provide unambiguous evidence for the νμ↔ντ oscillation by looking at the appearance of ντ in a pure νμ beam. The detector is located on the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. The apparatus consists of a target made of lead/emulsion-films bricks complemented by electronic detectors. The neutrino interaction inside the bricks is tagged using the electronic trackers. In August 2006, a short CNGS run was successfully performed and a first sample of neutrino events was collected. Experiment description and results from the first CNGS run are reported in details.

The OPERA experiment

The aim of the OPERA experiment is to provide unambiguous evidence for the ν μ ↔ ν τ oscillation by looking at the appearance of ν τ in a pure ν μ beam. This oscillation will be sought in the region of the oscillation parameters indicated by the atmospheric neutrino results. The experiment is part of the CNGS (CERN Neutrino beam to Gran Sasso) project. The ν μ beam produced at CERN will be sent towards the Gran Sasso underground laboratory, where the OPERA detector is under construction. The detector, the physics potential, and performance for neutrino oscillation studies including the subleading ν μ ↔ ν e search are presented.

Global analysis of solar and atmospheric neutrino data

A global analysis of solar (including the recent SNO result), atmospheric, and reactor neutrino data is presented in terms of three-and four-neutrino oscillations. We first present the allowed regions of solar and atmospheric oscillation parameters assuming three-neutrino families, showing that in this framework it is possible to reconcile the two anomalies and providing an unified fit of all the observables at a time. Then, we consider scenarios where a sterile neutrino is added to the three standard ones and the mass spectra present two separate doublets. We evaluate the allowed active-sterile admixture in both solar and atmospheric oscillations, showing that, although the Super-Kamiokande data disfavor both the pure νμ→νs atmospheric channel and, in combination with SNO, the pure νe→νs solar channel, the result from the combined analysis still favors close-to-pure active and sterile oscillations and disfavors oscillations into a near-maximal active-sterile admixture.