Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.     

Measurement of the ratio of inclusive cross sections sigma(pp --> Z + b jet)/sigma(pp --> Z + jet) at square root(s) = 1.96 TeV

Using the data collected with the D0 detector at square root(s) = 1.96 TeV, for integrated luminosities of about 180 pb(-1), we have measured the ratio of inclusive cross sections for pp --> Z + b jet to pp --> Z + jet production. The inclusive Z + b-jet reaction is an important background to searches for the Higgs boson in associated ZH production at the Fermilab Tevatron collider. Our measurement is the first of its kind, and relies on the Z --> e+ e- and Z --> mu+ mu- modes. The combined measurement of the ratio yields 0.021+/-0.005 for hadronic jets with transverse momenta pT > 20 GeV/c and pseudorapidities absolute value(eta) < 2.5, consistent with next-to-leading-order predictions of the standard model.     

Measurement of the WW production cross section in pp collisions at square root[s]=1.96 TeV

We present a measurement of the W boson pair-production cross section in pp collisions at a center-of-mass energy of sqrt[s]=1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224-252 pb(-1) depending on the final state (ee, emu, or mumu). We observe 25 candidates with a background expectation of 8.1+/-0.6(stat)+/-0.6(syst)+/-0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3x10(-7), equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8(+4.3)(-3.8)(stat)+1.2-0.9(syst)+/-0.9(lum) pb, in agreement with predictions from the standard model.     

Enantioselective analysis of methadone in saliva by liquid chromatography-mass spectrometry

Saliva was tested and evaluated as a biological matrix for methadone (Mtd) monitoring. Conventional method using a narrow bore C18 column, and an enantioselective method using a narrow bore alpha1-acid glycoprotein column, were developed using liquid chromatography coupled with a mass spectromeric (MS) detector. After optimisation of MS conditions by flow injection analysis, selected ion monitoring detection was used to enhance sensitivity. The total Mtd concentration and the enantiomeric ratio in saliva were validated using an experimental design. The methods were applied to samples provided by heroin addicts undergoing a Mtd treatment. Results on total Mtd determination showed a very poor correlation between saliva and serum, whereas the enantiomeric ratios of Mtd gave a very good one.     

Spectrophotometric determination of ethanol in blood using a flow-injection system with an immobilized enzyme (alcohol dehydrogenase) reactor coupled to an on-line dialyser

The determination of ethanol in whole blood without pretreatment using spectrotometric detection with an immobilized enzyme reactor coupled to an on-line dialyser is described. Optimum working conditions are given. The effects of the injection volume and the flow-rate on the peak height using the dialyser were investigated. A good linear calibration graph over the ethanol concentration range 3–40 μg ml^?1 was observed; these concentrations correspond to 0.3?4.0 g of ethanol per 1000 g of whole blood prior to dilution. For comparison, whole blood samples were analysed by gas chromatography with direct injection. The effect of temperature on the peak height was also studied in a system without the dialyser.     

High resolution photoabsorption and photofragment fluorescence spectroscopy of water between 10.9 and 12 eV

This work presents absorption and photofragment fluorescence spectra of water (H2O and D2O) simultaneously recorded at rotational resolution and at room temperature, by means of a synchrotron radiation source in the range 10.9-12 eV, covering the nd intense series from n=3 to 8. The Rydberg states observed are assigned in the light of the most advanced theoretical work available [M. S. Child, Philos. Trans. R. Soc. London, Ser. A 355, 1623 (1997)], and by reference to the stretching and bending mode progressions. Comparison between absorption and fluorescence spectra is shown to reveal a fast predissociation mechanism involving the linear 3pb2 1B2 state, and permits the identification of its (0,14,0) vibrational level observed in the absorption spectra.     

Search for doubly charged higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in pp collisions at sqrt[s]=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.     

Parametric study of horizontally vibrated grain packings: comparison between Discrete Element Method and experimental results

Numerical and experimental studies have been undertaken to analyze three parameters controlling the compaction of granular media submitted to sinusoidal horizontal vibrations. We have characterized the influence of the dimensionless acceleration Γ, the geometry of the container and the friction coefficients on the grain velocities and on the packing densities. Above a critical acceleration Γ, the velocities increases with Γ. For low values of Γ, the surface layers are compacted, whereas the bottom layers remain at their initial density. For high values of Γ, the bottom layers get compacted, the surface layers are fluidized so that the bulk dynamic and relaxed densities decreased. In the same way, the effect of the dimensions of the container and of the friction coefficients on the packing properties has been studied for given heights of sand, acceleration and frequency. It has been shown that the influence of the two last parameters is similar to that of acceleration. The numerical results given by the Discrete Element Method appear to be in good agreement with experimental results.     

Evaluation of a sheathless nanospray interface based on a porous tip sprayer for CE-ESI-MS coupling

The hyphenation of capillary electrophoresis (CE) with mass spectrometry (MS) is a powerful method to obtain high efficient, sensitive, and selective analyses. The successful coupling with electrospray ionization (ESI) source requires closed electric circuits for both the CE separation and the ESI processes. A wide range of interfaces has been proposed to satisfy this requirement. Among them, the new high sensitivity porous sprayer based on a porous tip achieves the electric connection by inserting the capillary outlet made of a porous material into an ESI needle filled with a conductive liquid and independently grounded. This device is compatible with the minute flow rates exhibited in CE and therefore makes possible the use of a nano-electrospray behavior. In this work, this interface was evaluated for hyphenating a CE with a single quadrupole MS instrument for low molecular weight analytes. Investigations aimed at highlighting the most influent parameters thanks to a design of experiments, reaching the best performance in terms of sensitivity and stability. MS signal intensities of various pharmaceutical compounds (e.g. amphetamines, β-blockers) emphasized high sensitivity and efficiency, while repeatability, expressed as relative standard deviation of corrected heights and areas, was suitable for quantitative purposes (<5%).     

Spectroscopic characterization of microscopic hydrogen-bonding disparities in supercritical water

The local hydrogen-bonding environment in supercritical water (380 degrees C, 300 bars, density 0.54 gcm3) was studied by x-ray Raman scattering at the oxygen K edge. The spectra are compared to those of the gas phase, liquid surface, bulk liquid, and bulk ice, as well as to calculated spectra. The experimental model systems are used to assign spectral features and to quantify specific local hydrogen-bonding situations in supercritical water. The first coordination shell of the molecules is characterized in more detail with the aid of the calculations. Our analysis suggests that approximately 65% of the molecules in supercritical water are hydrogen bonded in configurations that are distinctly different from those in liquid water and ice. In contrast to liquid water the bonded molecules in supercritical water have four intact hydrogen bonds and in contrast to ice large variations of bond angles and distances are observed. The remaining approximately 35% of the molecules exhibit two free O-H bonds and are thus either not involved in hydrogen bonding at all or have one or two hydrogen bonds on the oxygen side. We determine an average O-O distance of 3.1+/-0.1 A in supercritical water for the H bonded molecules at the conditions studied here. This and the corresponding hydrogen bond lengths are shown to agree with neutron- and x-ray-diffraction data at similar conditions. Our results on the local hydrogen-bonding environment with mainly two disparate hydrogen-bonding configurations are consistent with an extended structural model of supercritical water as a heterogeneous system with small patches of bonded molecules in various tetrahedral configurations and surrounding nonbonded gas-phase-like molecules.