Search

The observed scaling violations of the nucleon structure functionF 2 and $$\bar q$$ have been analysed in the framework of perturbative QCD to determine the shape and magnitude of the gluon distribution. The data are in good agreement with leading order QCD, and the simultaneous use ofF 2 and $$\bar q$$ structure functions permits, for the first time, a reliable determination of the gluon structure function.

A study of prompt neutrino events from 400 GeV protons on a beam-dump is presented. The ratio of electron- to muon-neutrino rates is 0.86±0.14, in agreement withe−μ universality. The anti-neutrino to neutrino flux ratio is $$\bar v_\mu /v_\mu = 0.81 \pm 0.19$$ . The absolute rates and distributions observed are shown to be in quantitative agreement with the known properties of charmedquark production in hadron collisions.

A large sample of opposite-sign dimuons, produced by the interaction of neutrinos and antineutrinos in iron, is analysed. The data agree very well with the hypothesis that the extra muon is the product of charm decay. They yield information on the strength and space-time structure of the charmproducing weak current. The strange-sea structure functionxs(x) is determined. The difference between neutrino and antineutrino dimuon production is analysed to provide a value of the Kobayashi-Maskawa weak mixing angleθ2.

The CDHS neutrino detector has been used to measure events originating in a tank of liquid hydrogen and in the iron of the detector. Total cross-sections, differential cross-sections, and structure functions are given for hydrogen and compared with those in iron. The measurements are in agreement with the expectations of the quark parton model. No significant differences indicative of nuclear binding effects in corresponding structure functions of protons and iron are observed. This may be of special interest in the case of the sea structure functions, since large differences are expected in some models.

Experimental evidence for the diffractive production ofΨmesons in weak neutral current reactions is reported. The spectrum-averaged cross section for this process isσdiff = (4.2±1.5) × 10−41cm2/nucleon, in agreement with gluonfusion models, but at variance with vector dominance calculations.

We have searched for ν μ oscillations by comparing the rates of ν gm charged-current interactions in two detectors located 130 and 885 m from the target, which was struck by a 9.2 GeV/ c proton beam from the CERN Proton Synchroton. No evidence for ν μ oscillations was found. At the 90% confidence level, Δm 2 values between 0.26 and 90 eV 2 are excluded for maximal mixing. The most restrictive limit on the neutrino mixing-angle parameter sin 2 2 θ is 0.053 at Δm 2 =2.5 eV 2 .

In an investigation of self-diffusion in bcc $\ensuremath{\beta}$-Ti single crystals by means of both quasielastic and inelastic neutron scattering, the elementary diffusion jump has been determined directly, and the lattice vibrations which trigger the jump have been elucidated. The elementary jump for self-diffusion is a simple \textonehalf{} [111] jump into a nearest-neighbor vacancy. The reason for the anomalously fast self-diffusion is a fluctuation of $\ensuremath{\omega}$-phase type which facilitates jumps into neighboring vacancies.

The scaling violations of the structure functionsF 2,xF 3, and $$\bar q$$ , as measured in deep-inelastic neutrino-nucleon scattering at high hadron massW, have been compared with the predictions of QCD and other candidate field theories of strong interactions. Non-asymptotically free theories with scalar and vector gluons are incompatible with the data. This leaves QCD as the only field theory that gives a consistent description of all the observed scaling violations. The data do not, however, permit a sensitive test of the existence of the gluon self-coupling.

From exposures of the CDHS detector at the CERN SPS we have obtained 367μ + μ − events in neutrino beams and 73μ + μ + events in an antineutrino beam. The magnitude of a prompt like-sign signal has been controversial in the past and moreover could not be explained by known production mechanisms. A critical discussion of the experimental situation is given. We have tried to reduce the systematic uncertainties of previous experiments and to get more information on the dependence of the signal with energy and the muon momentum cut-off. This experiment yields a signal of 2.8σ (2.4σ) of prompt like-sign dimuon events in the case of neutrinos (antineutrinos). The rate to charged current events is of the order of 10−4 forp μ 100 GeV. The prompt signal has all the properties expected from the production and decay of charm-anticharm events. The magnitude, however, is substantially higher then the prediction of perturbative QCD but lower than some other experiments.

A furnace for growing single crystals of metals and metal alloys by the floating zone technique has been constructed. This makes it possible to grow single crystals of materials with a phase transition in their high temperature phase in situ on a neutron scattering instrument. Without the crystals being cooled below their transition temperature they can be oriented and a neutron scattering experiment can be performed. The typical crystal size is about 5 cm 3 . The furnace is designed for continuous operation up to 2000 K under ultrahigh vacuum or high purity gas atmospheres. It gives access to a 360° neutron scattering plane with a maximum angle of inclination of ±20°.

The energy resolution and response of a segmented iron-scintillator total absorption calorimeter has been measured for pion energies from 10 to 140 GeV and for electron energies up to 50 GeV. A procedure has been found to weight individual counter responses for hadron showers which results in improved energy resolution at high energies and a nearly linear dependence of response on hadron energy above 30 GeV. There is evidence in the data that this weighting procedure compensates for fluctuations in energy deposition due to the electromagnetic component of the hadronic shower. For an iron sampling thickness of 2.5 cm the hadron energy resolution follows a 0.58 E law, while the resolution for electromagnetic showers is 0.23 E .

Inclusive charged-current interactions of high-energy neutrinos and antineutrinos have been studied with high statistics in a counter experiment at the CERN Super Proton Synchrotron. The energy dependence of the total cross-sections, the longitudinal structure function, and the nucleon structure functionsF2,xF3, and\(\bar q^{\bar v} \) are determined from these data. The analysis of theQ2-dependence of the structure functions is used to test quantum chromodynamics, to determine the scale parameter Λ and the gluon distribution in the nucleon.

The cross section ratios of neutral and charged current interactions induced by neutrinos and antineutrinos in iron have been measured in the 200 GeV narrow-band beam at the CERN SPS. We findRv=0.301±0.007 andRv=0.363±0.015 for a hadron energy cut of 10 GeV. The results are in agreement with the standard model of electroweak interactions. In the\(\overline {MS} \) renormalization scheme at the scale of theW boson mass\(\sin ^2 \hat \theta _W \left( {m_W } \right) = 0.226 \pm 0.012\) is obtained, where the error represents the experimental uncertainty. The theoretical uncertainty is estimated to beΔsin2θW=±0.006.

As a common feature,group IVb elements — Zr, Ti, Hf — exhibit a martensitic phase transition from the closed packed hcp structure (stable at low temperature) to the more open bcc structure. Diffusion properties in these metals are dominated by this phase transition. For instance the Zr self-diffusion increases by five orders of magnitude at the phase transition at about 840°C. A similar behaviour is known for most of the metal impurities in Zr of which the diffusivities are in the same order of magnitude as for Zr self-diffusion.

Decomposition of a palladium compound by ion irradiation has been used to catalyze electroless plating on polyimide. First, palladium-acetylacetonate or -acetate is spin-coated on a polyimide substrate. The thin resist film is then irradiated through a mask with He or Ar ions of 100 keV energy. After washing off the film parts which were not exposed to the ion beam, copper is deposited on the catalyzed polyimide substrate in an alkaline electroless plating bath. When using alkaline resistant polyimide, copper lines several microns thick can be plated. The chemical surface composition of the Pd-compounds after ion beam exposure has been investigated with ESCA. It has been found that the Pd is partially reduced. Pd-acetate is more effective to form catalytic sites than Pd-acetylacetonate.

A new measurement of the ratio R = σ L / σ T of longitudinal and transverse structure functions in neutrino interactions on iron between 30 and 190 GeV neutrino energy is reported. The result is given as a function of the scale parameter x and the inelasticity ν of the interaction. The average value is R = 0.10 ± 0.07 around ν ≈ 50 GeV and is in accordance with a prediction from the QCD theory.

In the interactions of 400 GeV/c protons with copper nuclei, a flux of prompt neutrinos is observed. The reactions produced by these neutrinos in our apparatus appear consistent with those of electron- and muon-neutrinos. The prompt neutrino fluxes are interpreted as being due to associated production and subsequent semileptonic decay of charmed hadrons. The prompt flux ratio $$\bar v_\mu /v_\mu = 0.46_{ - 0.16}^{ + 0.21} $$ suggests a sizeable production of charmed baryons near the forward direction. The ratio of prompte −+e + toµ −+µ + event rates is 0.64 −0.15 +0.22 , where unity is expected frome-μ universality.

We have calibrated a magnetized iron-scintillator sandwhich calorimeter in a hadron beam, finding an energy resolution equal to 16% fwhm at 140 GeV with 5 cm sampling. The hadron energy resolution (fwhm/mean) improves as E − 1 2 between 15 and 140 GeV. No effect due to the magnetic field was observed. Longitudinal and lateral shower containment were also investigated.

With quasielastic neutron scattering the elementary diffusion jump (length and direction) and the jump frequency in bcc \ensuremath{\beta}-Ti single crystals have been determined at temperatures between 1460 and 1580 \ifmmode^\circ\else\textdegree\fi{}C. Supplementary measurements on polycrystalline samples extended the temperature region down to 1100 \ifmmode^\circ\else\textdegree\fi{}C. The elementary diffusion jump is a jump into a nearest-neighbor vacancy. An admixture of 10--15 % jumps into next-nearest-neighbor vacancies is compatible with the experiments. Comparison of derived diffusivities with results from tracer measurements shows satisfactory agreement.

Right handed weak quark currents coupled to the usual left handed weak lepton current would be seen in inclusive antineutrino scattering on nuclei as a contribution at largey with the quark (not antiquark) structure function. We do not see such a term, and can therefore put an upper limit on the relative strengths of such right handed currents:\(\varrho ^2 = \frac{{\sigma _R }}{{\sigma _L }}< 0.009\), 90% confidence. This measurement puts limits on the mixing angle of left-right symmetric models. In distinction to similar limits derived from muon decay or β decay, our limits are also valid if the right handed neutrino is heavy.