We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions (ν μ n → μ − p andν μ p → μ + n) using a set of experimental data collected by the NOMAD Collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly carbon) normalizing it to the total ν μ (ν μ ) charged-current cross section. The results for the flux-averaged QEL cross sections in the (anti)neutrino energy interval 3-100 GeV are σ qel ν μ = (0.92 ± 0.02(stat) ± 0.06(syst)) × 10 −38 cm 2 and σ qel ν μ = (0.81 ± 0.05(stat) ± 0.09(syst)) × 10 −38 cm 2 for neutrino and antineutrino, respectively. The axial mass parameter M A was extracted from the measured quasi-elastic neutrino cross section. The corresponding result is M A = 1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross section and extracted from the pure Q 2 shape analysis of the high purity sample of ν μ quasielastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured M A is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of M A is lower than those recently published by K2K and MiniBooNE Collaborations. However, within the large errors quoted by these experiments on M A , these results are compatible with the more precise NOMAD value.PACS 13.15.+g · 25.30.Pt

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km. The measurement is based on data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies.An arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (6.5 ± 7.4 (stat.) +8.3 −8.0 (sys.)) ns was measured corresponding to a relative difference of the muon neutrino velocity with respect to the speed of light (v − c)/c = (2.7 ± 3.1 (stat.) +3.4 −3.3 (sys.)) × 10 −6 . The above result, obtained by comparing the time distributions of neutrino interactions and of protons hitting the CNGS target in 10.5 µs long extractions, was confirmed by a test performed at the end of 2011 using a short bunch beam allowing to measure the neutrino time of flight at the single interaction level.

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.

We present the results of a search for ν µ → ν e oscillations in the NOMAD experiment at CERN. The experiment looked for the appearance of ν e in a predominantly ν µ wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are m 2 < 0.4 eV 2 for maximal mixing and sin 2 (2θ) < 1.4 × 10 −3 for large m 2. This result excludes the LSND allowed region of oscillation parameters with m 2 10 eV 2 .

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.

We report upon the realization of a novel fast nondeterministic random number generator whose randomness relies on the intrinsic randomness of the quantum physical processes of photonic emission in semiconductors and subsequent detection by the photoelectric effect. Timing information of detected photons is used to generate binary random digits-bits. The bit extraction method based on the restartable clock method theoretically eliminates both bias and autocorrelation while reaching efficiency of almost 0.5 bits per random event. A prototype has been built and statistically tested.

We report on a search for heavy neutrinos (ν 4 ) produced in the decay D s → τ ν 4 at the SPS proton target followed by the decay ν 4 → ν τ e + e − in the NOMAD detector. Both decays are expected to occur if ν 4 is a component of ν τ . From the analysis of the data collected during the 1996-1998 runs with 4.1 × 10 19 protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the ν 4 mass range from 10 to 190 MeV. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.Key words: neutrino mixing, neutrino decay IntroductionIn the Standard Model all fundamental fermions have a right-handed component that transforms as an isosinglet under the SU(2) L gauge group except neutrinos, which are observed only in left-handed form. However, heavy neutrinos which are decoupled from W and Z bosons and hence are mostly isosinglet (sterile) arise in many models that attempt to unify the presently known interactions into a single gauge scheme, such as Grand Unified Theories or Superstrings inspired models [1]. They are also predicted in models trying to solve the problem of baryo-or leptogenesis in the Universe, in many extended electroweak models, such as left-right symmetric and see-saw models [1]. Their masses are predicted to be within the GeV − TeV range. The existence of a light ( eV or ≪ eV) sterile neutrino is expected in schemes that attempt to solve the presently observed indication from atmospheric, solar and LSND experiments that neutrinos are massive, see e.g. [2] and references therein. More generally one can also look for an isosinglet neutrino with intermediate mass such as in the keV − MeV range. For instance, such neutrinos with masses in the range 1 -40 keV were recently considered as a candidate for warm dark matter [3].If heavy neutrinos exist, many crucial questions arise. For example, for massive neutrinos the flavour eigenstates (ν e , ν µ , ν τ , ...) need not coincide with the mass eigenstates (ν 1 , ν 2 , ν 3 , ν 4 ...), but would, in general, be related through a unitary transformation. Such a generalised mixing:could result in neutrino oscillations when the mass differences are small, and in decays of heavy neutrinos when the mass differences are large. The motivation and purpose of this work is to search for a neutral heavy lepton ν 4 which is dominantly associated with the third generation of light neutrinos, ν τ , via the mixing term |U τ 4 | 2 . If such a particle exists it might be produced in the decay D s → τ ν 4 at the SPS proton target followed by the decay ν 4 → ν τ e + e − in the NOMAD detector as is illustrated in Figure 1 (see also Section 3). The experimental signature of these events is clean and they can be selected with small background due t...

We present our new measurement of the cross-section for charm dimuon production in neutrino-iron interactions based upon the full statistics collected by the NO-MAD experiment. After background subtraction we observe 15,344 charm dimuon events, providing the largest sample currently available. The analysis exploits the large inclusive charged current sample -about 9 × 10 6 events after all analysis cuts -and the high resolution NOMAD detector to constrain the total systematic uncertainty on the ratio of charm dimuon to inclusive Charged Current (CC) crosssections to ∼ 2%. We also perform a fit to the NOMAD data to extract the charm production parameters and the strange quark sea content of the nucleon within the NLO QCD approximation. We obtain a value of m c (m c ) = 1.159 ± 0.075 GeV/c 2 for the running mass of the charm quark in the MS scheme and a strange quark sea suppression factor of κ s = 0.591 ± 0.019 at Q 2 = 20 GeV 2 /c 2 .