Experimental application of sum rules for electron energy loss magnetic chiral dichroism

We present a derivation of the orbital and spin sum rules for magnetic circular dichroic spectra measured by electron energy loss spectroscopy in a transmission electron microscope. These sum rules are obtained from the differential cross section calculated for symmetric positions in the diffraction pattern. Orbital and spin magnetic moments are expressed explicitly in terms of experimental spectra and dynamical diffraction coefficients. We estimate the ratio of spin to orbital magnetic moments and discuss first experimental results for the Fe L_{2,3} edge.Comment: 11 pages, 2 figure

Energy-loss magnetic chiral dichroism (EMCD): Magnetic chiral dichroism in the electron microscope

A new technique called energy-loss magnetic chiral dichroism (EMCD) has recently been developed [P. Schattschneider, et al. Nature 441, 486 (2006)] to measure magnetic circular dichroism in the transmission electron microscope (TEM) with a spatial resolution of 10 nm. This novel technique is the TEM counterpart of x-ray magnetic circular dichroism, which is widely used for the characterization of magnetic materials with synchrotron radiation. In this paper we describe several experimental methods that can be used to measure the EMCD signal [P. Schattschneider, et al. Nature 441, 486 (2006); C. Hébert, et al. Ultramicroscopy 108(3), 277 (2008); B. Warot-Fonrose, et al. Ultramicroscopy 108(5), 393 (2008); L. Calmels, et al. Phys. Rev. B 76, 060409 (2007); P. van Aken, et al. Microsc. Microanal. 13(3), 426 (2007)] and give a review of the recent improvements of this new investigation tool. The dependence of the EMCD on several experimental conditions (such as thickness, relative orientation of beam and sample, collection and convergence angle) is investigated in the transition metals iron, cobalt, and nickel. Different scattering geometries are illustrated; their advantages and disadvantages are detailed, together with current limitations. The next realistic perspectives of this technique consist of measuring atomic specific magnetic moments, using suitable spin and orbital sum rules, [L. Calmels, et al. Phys. Rev. B 76, 060409 (2007); J. Rusz, et al. Phys. Rev. B 76, 060408 (2007)] with a resolution down to 2 to 3 n

Experimental study of solubility of elemental sulphur in methane

International audienceThe chemical engineering department of LaTEP has been working for many years on theproblem of sulphur deposition especially in natural gas network [1, 2]. The solid sulphurappears immediately downstream of a pressure reduction facility. One of the hypothesesproposed to explain the solid formation, based on a thermodynamic approach, is thedesublimation of sulphur. During gas expansion, both pressure and temperature decrease.Consequently the gas may become over saturated in sulphur. Because we are below thetemperature of sulphur triple point, part of the gaseous sulphur can be transformed into solidparticles. Thus, it is important to obtain solubility data of sulphur in natural gases. Methane isthe major natural gas component. So, it is of importance to measure solubility of elementalsulphur in CH4. In this paper experimental measurements up to a pressure and temperature of30 MPA and 363.15 K are presented.The principle of the experimental pilot can be resumed following three steps: saturationof the gas with sulphur, trap of all the dissolved gaseous sulphur and finally quantification.Although the principle is simple, experimental difficulties occur at the three steps. A variablevolume equilibrium cell is used to saturate the gas with sulphur. Since sulphur solubility valueis weak in gas transport conditions, the volume of the cell is necessarily big (0.5 Litre). Thepressure of the equilibrium cell is held constant thanks to a piston during the trapping step. Anoriginal gaseous sulphur trapping method was developed. It is based on the reactiveabsorption of the gaseous sulphur with solvent. Indeed, the gas bubbles into a liquid solutionwhich traps gaseous sulphur. Finally, the solution which contains a standard is analysed bygas chromatography and sulphur is quantified. The total volume of the gas withdrawn isdetermined by a position transducer placed on the autoclave. Then, the sulphur solubilityvalue is calculated

Measurement of Neutrino-Electron Scattering Cross-Section with a CsI(Tl) Scintillating Crystal Array at the Kuo-Sheng Nuclear Power Reactor

The $\bar{\nu}_{e}-e^{-}$ elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal array having a total mass of 187kg. The detector was exposed to an average reactor $\bar{\nu}_{e}$ flux of $\rm{6.4\times 10^{12} ~ cm^{-2}s^{-1}}$ at the Kuo-Sheng Nuclear Power Station. The experimental design, conceptual merits, detector hardware, data analysis and background understanding of the experiment are presented. Using 29882/7369 kg-days of Reactor ON/OFF data, the Standard Model(SM) electroweak interaction was probed at the squared 4-momentum transfer range of $\rm{Q^2 \sim 3 \times 10^{-6} ~ GeV^2}$. The ratio of experimental to SM cross-sections of $\xi =[ 1.08 \pm 0.21(stat)\pm 0.16(sys)]$ was measured. Constraints on the electroweak parameters $(g_V , g_A)$ were placed, corresponding to a weak mixing angle measurement of \s2tw = 0.251 \pm 0.031({\it stat}) \pm 0.024({\it sys}) . Destructive interference in the SM \nuebar -e process was verified. Bounds on anomalous neutrino electromagnetic properties were placed: neutrino magnetic moment at \mu_{\nuebar}< 2.2 \times 10^{-10} \mu_{\rm B} and the neutrino charge radius at -2.1 \times 10^{-32} ~{\rm cm^{2}} < \nuchrad < 3.3 \times 10^{-32} ~{\rm cm^{2}}, both at 90% confidence level.Comment: 18 Figures, 7 Tables; published version as V2 with minor revision from V

The Minimal Supersymmetric Standard Model: Group Summary Report

CONTENTS: 1. Synopsis, 2. The MSSM Spectrum, 3. The Physical Parameters, 4. Higgs Boson Production and Decays, 5. SUSY Particle Production and Decays, 6. Experimental Bounds on SUSY Particle Masses, 7. References.Comment: 121 pages, latex + epsfig, graphicx, axodraw, Report of the MSSM working group for the Workshop "GDR-Supersym\'etrie",France. Rep. PM/98-4

In situ commissioning of the ATLAS electromagnetic calorimeter with cosmic muons

In 2006, ATLAS entered the {\it in situ} commissioning phase. The primary goal of this phase is to verify the detector operation and performance with cosmic muons. Using a dedicated cosmic muon trigger from the hadronic Tile calorimeter, a sample of approximately $120\,000$ events was collected in several modules of the barrel electromagnetic (EM) calorimeter between August 2006 and March 2007. As cosmic events are generally non-projective and arrive asynchronously with respect to the trigger clock, methods to improve the standard signal reconstruction for this situation are presented. Various selection criteria for projective muons and clustering algorithms have been tested, leading to preliminary results on calorimeter uniformity in $\eta$ and timing performance

Determination of the branching ratios Γ(KL→3π0)/Γ(KL→π+π−π0)\Gamma (K_L \to 3 \pi^0) / \Gamma (K_L \to \pi^+ \pi^- \pi^0) and Γ(KL→3π0)/Γ(KL→πeν)\Gamma (K_L \to 3 \pi^0) / \Gamma (K_L \to \pi e \nu )

Improved branching ratios were measured for the $K_L \to 3 \pi^0$ decay in a neutral beam at the CERN SPS with the NA31 detector: $\Gamma (K_L \to 3 \pi^0) / \Gamma (K_L \to \pi^+ \pi^- \pi^0) = 1.611 \pm 0.037$ and $\Gamma (K_L \to 3 \pi^0) / \Gamma (K_L \to \pi e \nu ) = 0.545 \pm 0.010$. From the first number an upper limit for $\Delta I =5/2$ and $\Delta I = 7/2$ transitions in neutral kaon decay is derived. Using older results for the Ke3/K$\mu$3 fraction, the 3$\pi^0$ branching ratio is found to be $\Gamma (K_L \to 3 \pi^0 )/ \Gamma_{tot} = (0.211 \pm 0.003)$, about a factor three more precise than from previous experiments

Position resolution and particle identification with the ATLAS EM calorimeter

In the years between 2000 and 2002 several pre-series and series modules of the ATLAS EM barrel and end-cap calorimeter were exposed to electron, photon and pion beams. The performance of the calorimeter with respect to its finely segmented first sampling has been studied. The polar angle resolution has been found to be in the range 50-60 mrad/sqrt(E (GeV)). The neutral pion rejection has been measured to be about 3.5 for 90% photon selection efficiency at pT=50 GeV/c. Electron-pion separation studies have indicated that a pion fake rate of (0.07-0.5)% can be achieved while maintaining 90% electron identification efficiency for energies up to 40 GeV.Comment: 32 pages, 22 figures, to be published in NIM

Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method

This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1$ of the true values and the fractional energy resolution is $[(58\pm3)/\sqrt{E}+(2.5\pm0.3)$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM