Backward particle production in neutrino neon interactions

Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model.     

Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

Phase-field modeling of void evolution and swelling in materials under irradiation

Void swelling is an important phenomenon observed in both nuclear fuels and cladding materials in operating nuclear reactors. In this work we develop a phase-field model to simulate void evolution and void volume change in irradiated materials. Important material processes, including the generation of defects such as vacancies and self-interstitials, their diffusion and annihilation, and void nucleation and evolution, have been taken into account in this model. The thermodynamic and kinetic properties, such...     

A search for the exotic Ξ<Superscript>−−</Superscript> (1860) in the hyperon beam experiment WA89(1860) in the hyperon beam experiment WA89

We report on a high statistics search for the Ξ^??(1860) resonance in Σ^?-nucleus collisions at 340 GeV/c. No evidence for this resonance is found in our data sample which contains 676000 Ξ^? candidates above bakground. For the decay channel Ξ^??(1860)→Ξ^? π ^? and the kinematic range 0.15<xF<0.9 we find a 3σ upper limit for the production cross section of 3.1 and 3.5 μb per nucleon, for reactions with carbon and copper, respectively.     

Double prompt photon production at high transverse momentum byπ − on protons at 280 GeV/c

A search for pairs of highp _T prompt photons produced in hydrogen by a 280 GeV/c incidentπ ^- beam has been carried out using a fine-grained electromagnetic calorimeter and the Omega spectrometer at the CERN SPS. Clear evidence for the existence of such events is found with a six standard deviation signal forp _T >3.0 GeV/c. The cross-sections are consistent with beyond leading order QCD calculations. A discussion on the determination of α _s is also presented.     

The structure of events triggered by direct photons in π− p, π+ p andpp collisions at 280 GeV/c

The structure of events associated with the production of direct photons in π^? p, π⁺ p andpp reactions of 280 GeV/c has been studied using data from the WA 70 experiment at the CERN SPS. Results are presented on the distributions of the fractional momenta of the colliding partons and on the fragmentation of the recoil jet and a comparison is made with predictions using the structure functions of Duke and Owens in the Lund Monte Carlo with string fragmentation.     

Micromegas prototypes with thermo-bond film separators

In this paper we report the results of Micromegas prototypes constructed by attaching micromesh to an anode using thermo-bond films. The excellent metal attaching ability and good dielectical property of this kind of film make it a promising material to be used as avalanche gap spacers. Several prototypes are successfully made. The electron transmission properties are first studied and then the gas gain is measured in argon-isobutane mixtures. The maximum gain of more than 10⁴ is easily obtained. The energy resolutions for ⁵⁵Fe 5.9 keV K_α ray can be better than 20% over one magnitude in gain for different operational gas mixtures and the best energy resolution of 13.7% (FWHM) can be achieved with the gas mixture of 94% argon concentration. The preliminary test results of the prototypes with sensitive area of 45 mm×45 mm without internal support show good uniformity across the sensitive area.     

Unraveling the roles of the acid medium, experimental probes, and terminal oxidant, (NH4)2[Ce(NO3)6], in the study of a homogeneous water oxidation catalyst

The oxidation of water catalyzed by [Ru(tpy)(bpy)(OH(2))](ClO(4))(2) (1; tpy = 2,2';6',2'-terpyridine; bpy = 2,2'-bipyridine) is evaluated in different acidic media at variable oxidant concentrations. The observed rate of dioxygen evolution catalyzed by 1 is found to be highly dependent on pH and the identity of the acid; e.g., d[O(2)]/dt is progressively faster in H(2)SO(4), CF(3)SO(3)H (HOTf), HClO(4), and HNO(3), respectively. This trend does not track with thermodynamic driving force of the electron-transfer reactions between the terminal oxidant, (NH(4))(2)[Ce(NO(3))(6)] (CAN), and Ru catalyst in each of the acids. The particularly high reactivity in HNO(3) is attributed to the NO(3)(-) anion: (i) enabling relatively fast electron-transfer steps; (ii) participating in a base-assisted concerted atom-proton transfer process that circumvents the formation of high energy intermediates during the O-O bond formation process; and (iii) accelerating the liberation of dioxygen from the catalyst. Consequently, the position of the rate-determining step within the catalytic cycle can be affected by the acid medium. These factors collectively contribute to the position of the rate-determining step within the catalytic cycle being affected by the acid medium. This offering also outlines how other experimental issues (e.g., spontaneous decay of the Ce(IV) species in acidic media; CAN/catalyst molar ratio; types of catalytic probes) can affect the Ce(IV)-driven oxidation of water catalyzed by homogeneous molecular complexes.