[en] The Large Hadron Collider (LHC) at CERN is the world largest particle accelerator. It will collide two proton beams at an unprecedented center of mass energy of 14 TeV. ATLAS is equipped with a charge particle tracking system built on two technologies: silicon and drift tube based detectors, composing the ATLAS Inner Detector (ID). The alignment of the tracking system poses a challenge as one should solve a linear equation with almost 36000 degrees of freedom. The required precision for the alignment of the most sensitive coordinates of the silicon sensors is just a few microns. This limit comes from the requirement that the misalignment should not worsen the resolution of the track parameter measurements by more than 20%. So far the proposed alignment algorithms are exercised on several applications. We will present the outline of the alignment approach and results using real data from cosmic rays and large scale computing simulation of physics samples mimicking the ATLAS operation during real data taking. The full alignment chain is tested using that stream and alignment constants are produced and validated within 24 hours. Cosmic ray data serves to produce an early alignment of the real ATLAS Inner Detector even before the LHC start up. The impact of the alignment on physics measurements will be discussed. (author)

[en] Self-induced GaN nanowires are grown by plasma-assisted molecular beam epitaxy, with In_xGa_1-xN quantum wells inserted to form an axial superlattice. From the ω-2θ scans of a laboratory x-ray diffraction experiment, we obtain the superlattice period, the thickness of the quantum wells, and the In content in this layer. The axial growth rate of the In_xGa_1-xN quantum wells is significantly enhanced, which we attribute to increased Ga diffusion along the nanowire sidewalls in the presence of In.

[en] This paper reports on the development of a fully optoelectronic optical sensor that has been used for investigations concerning quality control of the high velocity oxygen fuel (HVOF) flame spraying process. The authors focused on the following parameters: WoC with Co, CoCr, Ni at T < 500 C, and Cr₃C₂ with Ni-Cr, Ni at T < 900 C. Until recently, there was no non-destructive testing (NDT) approach for flame spraying available, which is a major drawback for many critical applications, like in the aerospace industry. For instance, while cooling down after spraying, cracks in the coatings may occur caused by strain. Furthermore, edges may cause similar damage to the coating. The idea was to provide the flame spraying industry with a measurement technology that is applicable in the workshop, has a contactless principle of operation and is fast compared to the commonly used metallography or scanning electron microscopy. The approach is designed for use close to the process, i.e. coating morphology was not the focus of the investigations. On the contrary, they tried to extract quality related information from surface microtopography which can be obtained in a non-destructive and affordable manner. Main points covered in this paper are theoretical considerations, the operational principles and construction of the sensor head, and quantitative metrology of surface damage such as variations in rms-roughness and cracks

[en] Ground- and excited-state proton transfers have been investigated with 8-hydroxy-1,3,6-pyrenetrisulfonate, POH, in sodium bis(2-ethylhexyl) sulfosuccinate, AOT, reversed micelle solubilized water pools in isooctane. Since POH is a much stronger acid in the singlet excited state, (POH)*, than in the ground state (pK/sub a/ = 7.2, pK/sub a/* = 0.5), excitation of POH by 1-5-mJ, 8-ns, 353-nm laser pulses, at pH values such that pK/sub a/* < pH < pK/sub a/, results in the dissociation of POH, governed by k/sub off/*. PO^- reprotonation rate, K/sub on/ values, have been determined by laser flash photolysis. In reversed micelles k/sub on/ values were found to depend on the water-to-AOT ratio(w values). Deuterium solvent isotope effects of 1.3 and 2.2 have been determined for k/sub on//k/sub on/(D₂O) in w = 33 and 12 AOT solubilized reversed micelles in isooctane. Combining these values with pK/sub a/ of POH led to isotope effects of 7.8 and 8.4 on k/sub off/ in the corresponding solutions. Steady-state and subnanosecond time-resolved fluorescence measurements have been utilized for assessing POH excited-state deprotonation, governed by k/sub off/*(D₂O), and reprotonation, governed by k/sub on/*(D₂O), in pure D₂O and in AOT entrapped water and AOT-d entrapped D₂O pools in isooctane. 51 references, 10 figures, 6 tables

[en] The mass of the top quark is a free parameter of the Standard Model. Its precise measurement is highly relevant, as it may reveal valuable insights into the nature of electroweak symmetry breaking due to a Yukawa coupling of almost unity. We review the final steps towards the world's most precise single measurement of m_top, which we aim to perform in lepton+jets final states using 9.7 fb^-1 of data recorded by the DOe detector in p anti p collisions at √(s)=1.96 TeV. To extract m_top, we apply the so-called matrix element technique, which offers superior statistical sensitivity. We review the cutting-edge methods of numerical integration we employ to meet the computational challenges of this measurement. Furthermore, we summarise our studies which lead to an improved understanding of systematic uncertainties from higher-order contributions, hadronisation and underlying event, initial and final state radiation, the dependency of the jet energy scale on the jet flavour, and others, resulting in a combined systematic uncertainty of below 1 GeV.

[en] To achieve the smallest systematic uncertainty possible for the final, most precise single measurement of m_top with the DOe detector, we capitalise on the advantage of the initial state at the Fermilab's Tevatron collider over that provided by the CERN's LHC, which features notably higher initial state radiation rates. Moreover, due to the dominance of quark-antiquark annihilation in production of t anti t pairs at the Tevatron, the rate of initial state radiation can be extrapolated to final state radiation. We use unfolded distributions in φ^* at different Q², extracted from 7.3 fb^-1 of Z→ll events recorded by DOe, to evaluate systematic uncertainties on m_top from initial and final state radiation. φ^* is a novel topological variable, which offers superb sensitivity to the transverse momentum of the Z boson at the lower end of the spectrum compared to conventional observables. Besides the m_top measurement, our studies are relevant and beneficial for the majority of analyses in the top sector at the Tevatron, and can possibly be extended to the final state radiation at the LHC.

[en] The latest measurements of the top quark mass in various decay channels of top quark pair production are presented. A brief introduction to the measurement techniques is given. The measurements are performed on data samples of up to 4.8 fb^-1 of integrated luminosity acquired by the Cdf and D 0 experiments in Run 2. of the Tevatron p p collider at a centre-of-mass energy of √ = 1.96 TeV. The Tevatron combination using up to 5.6 f b-1 of data results in a preliminary world average top quark mass of m top 173.3 ±1.1 GeV. This corresponds to a relative precision of about 0.6%.

[en] We analyze the line shape of x-ray diffraction profiles of GaN epitaxial layers with large densities of randomly distributed threading dislocations. The peaks are Gaussian only in the central, most intense part of the peak, while the tails obey a power law. The q^-3 decay typical for random dislocations is observed in the rocking curves with open detector. The entire profile is well fitted by a restricted random dislocation distribution. The densities of both edge and screw threading dislocations and the ranges of dislocation correlations are obtained

[en] We investigate the polarization dependence of the absorption, reflectance, and photoreflectance spectra of a compressively strained, M-plane, wurtzite GaN(11(bar sign)00) film grown by molecular-beam epitaxy on a γ-LiAlO₂(100) substrate. The measurements are done with the electric-field vector (E) of the probe light being parallel ((parallel sign)) and perpendicular ((perpendicular sign)) to the c axis of GaN, which lies in the growth plane. We observe a significant increase in the effective optical band gap of the M-plane GaN film for E(parallel sign)c compared to its value for E(perpendicular sign)c. This result is explained by including the effect of the M-plane biaxial compressive strain on the electronic band structure of GaN. We also determine the extraordinary refractive index of GaN at energies below its band gap from the reflectance measurements

[en] We describe a growth procedure utilizing molecular beam epitaxy that produces a (1100)-oriented MnAs layer on GaAs(111)B despite the incompatible unit mesh symmetry. An amorphous MnAs layer is deposited at a low temperature beyond the critical thickness for coherent growth. When solid-phase epitaxy is initiated by reducing the background As₄ pressure, the layer crystalizes in the M-plane orientation with its c axis being along the (112) directions of the substrate. The magnetization components associated with the coexisting c-axis orientations are independent of each other, suggesting that the structural domains are much larger in size than the atomic scales