We present a measurement of neutrino tridents, muon pairs induced by neutrino scattering in the Coulomb field of a target nucleus, in the Columbia-Chicago-Fermilab-Rochester neutrino experiment at the Fermilab Tevatron. The observed number of tridents after geometric and kinematic corrections, 37.0 ± 12.4, supports the standard-model prediction of 45.3 ± 2.3 events. This is the first demonstration of the W-Z destructive interference from neutrino tridents, and rules out, at 99% C.L., the V -A prediction without the interference.PACS numbers: 13.10.+q, 12.15.Ji, 14.80.Er, 25.30.Pt A neutrino trident is the scattering of a neutrino in the Coulomb field of a target nucleus (TV),

We present an improved determination of the proton structure functions F2 and xF3 from the CCFR ν-Fe deep inelastic scattering (DIS) experiment. Comparisons to high-statistics chargedlepton scattering results for F2 from the NMC, E665, SLAC, and BCDMS experiments, after correcting for quark-charge and heavy-target effects, indicate good agreement for x > 0.1 but some discrepancy at lower x. The Q 2 evolution of both the F2 and xF3 structure functions yields the quantum chromodynamics (QCD) scale parameter Λ NLO,(4) M S = 337 ± 28(exp.) M eV . This corresponds to a value of the strong coupling constant at the scale of mass of the Z-boson of αS(M 2 Z ) = 0.119 ± 0.002(exp.)±0.004(theory) and is one of the most precise measurements of this quantity.PACS numbers: 13.15.+g, 12.38. Qk, 24.85.+p, 25.30.Pt High-energy neutrinos are a unique probe for testing QCD and understanding the parton properties of nucleon structure. Combinations of neutrino and antineutrino scattering data are used to determine the F 2 and xF 3 structure functions (SFs) which determine the valence, sea, and gluon parton distributions in the nucleon [1,2]. The universalities of parton distributions can also be studied by comparing neutrino and charged-lepton scattering data. Past measurements have indicated that F ν 2 differs from F e/µ 2 by 10-20% in the low-x region. These differences are larger than the quoted experimental errors of the measurements and may indicate the need for modifications of the theoretical modeling to include higher-order or new physics contributions. QCD predicts the scaling violations (Q 2 dependence) of F 2 and xF 3 and, experimentally, the observed scaling violations can be tested against those predictions to determine α S [3] or the related QCD scale parameter, Λ QCD . The α S determination from neutrino scattering has a small theoretical uncertainty since the electroweak radiative corrections, scale uncertainties, and next-to-leading order (NLO) corrections are well understood.In this paper, we present an updated analysis of the Columbia-Chicago-Fermilab-Rochester (CCFR) collaboration neutrino scattering data with improved estimates of quark model parameters [4] and systematic uncertainties. The α S measurement from this analysis is one of the most precise due to the high energy and statistics of the experiment compared to previous measurements [5,6].

A high-statistics study by the Columbia-Chicago-Fermilab-Rochester Collaboration of opposite-sign dimuon events induced by neutrino-nucleon scattering at the Fermilab Tevatron is presented. A sample of 5044 v M and 1062 vv induced /i^/i 1 events with P^ > 9 GeV/c, P^2> 5 GeV/c, 30 < E v < 600 GeV, and

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...

This Letter reports the first direct observation of muon antineutrino disappearance. The MI-NOS experiment has taken data with an accelerator beam optimized for νµ production, accumulating an exposure of 1.71 × 10 20 protons on target. In the Far Detector, 97 charged current νµ events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3σ. The best fit to oscillation yields |∆m 2 | = [3.36 +0. 46 −0.40 (stat) ± 0.06(syst)] × 10 −3 eV 2 , 2 sin 2 (2θ) = 0.86 +0.11 −0.12 (stat) ± 0.01(syst). The MINOS νµ and νµ measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.PACS numbers: 14.60. Lm, 14.60.Pq, 14.60.St Observations by many experiments provide compelling evidence for neutrino oscillation [1][2][3][4][5][6][7][8][9]. This oscillation, a consequence of the quantum mechanical mixing of the neutrino mass and weak flavor eigenstates, is governed by the elements of the Pontecorvo-Maki-Nakagawa-Sakata matrix [10], parameterized by three mixing angles and a CP phase, and by two independent neutrino masssquared differences. As the measurement precision on oscillation parameters improves, so does the potential for observing new phenomena. In particular, measured differences between the neutrino and antineutrino oscillation parameters would indicate new physics. CPT symmetry, one of the most fundamental assumptions underlying the standard model, constrains the allowed differences in the properties of a particle and its antiparticle [11] and requires that their masses be identical. This symmetry has been extensively tested in other sectors, most notably the kaon sector [12]. Additionally, neutrinos passing through matter could experience nonstandard interactions [13] that alter the ν µ and ν µ disappearance probabilities and, thus, the inferred oscillation parameters [14].The MINOS experiment has used a ν µ beam to measure the larger (atmospheric) mass-squared difference |∆m 2 | = (2.32 +0.12 −0.08 ) × 10 −3 eV 2 and the mixing angle sin 2 (2θ) > 0.90 (90% confidence limit [C.L.]) through observation of ν µ disappearance [3, 15]. The corresponding antineutrino oscillation parameters are much less precisely known.This Letter describes the first direct observation of ν µ disappearance consistent with oscillation, yielding the most precise measurement to date of the larger antineutrino mass-squared difference. The only previous measurements from ν µ -tagged samples, providing weak constraints, come from the MINOS atmospheric neutrino sample [16] and an analysis of the ν µ component of the MINOS ν µ data sample [17,18]. The strongest indirect constraints come from a global fit [19], dominated by Super-Kamiokande data which measure the sum of atmospheric ν µ and ν µ interaction rates.For this measurement the NuMI beam line [20] was configured to produce a ν µ -enhanced beam. The current in the magnetic horns was configured to focus negative pions and kaons produced by 120 GeV protons incident on a graphite target. Most mesons travel ...