Alignment procedure of the LHCb Vertex Detector

LHCb is one of the four main experiments of the Large Hadron Collider (LHC) project, which will start at CERN in 2008. The experiment is primarily dedicated to B-Physics and hence requires precise vertex reconstruction. The silicon vertex locator (VELO) has a single hit precision of better than 10 micron and is used both off-line and in the trigger. These requirements place strict constraints on its alignment. Additional challenges for the alignment arise from the detector being retracted between each fill of the LHC and from its unique circular disc r/phi strip geometry. This paper describes the track based software alignment procedure developed for the VELO. The procedure is primarily based on a non-iterative method using a matrix inversion technique. The procedure is demonstrated with simulated events to be fast, robust and to achieve a suitable alignment precision.Comment: accepted for publication in NIM

LHCb VELO software alignment, Part III: the alignment of the relative sensor positions

The LHCb Vertex Locator contains 42 silicon sensor modules. Each module has two silicon sensors. A method for determining the relative alignment of the silicon sensors within each module from data is presented. The software implementation details are discussed. Monte-Carlo simulation studies are described that demonstrate an alignment precision of 1.3 micron is obtained in the sensor plane

Laser monitoring system for the ATLAS tile calorimeter

International audienc

LHCb VELO software alignment - PART II: the alignment of the VELO detector-halves

The software alignment of the Vertex Locator (VELO) is a critical component of the LHCb alignment strategy. This note demonstrates a potential algorithm to perform the alignment of the VELO detector-halves. The approach described in this document, and the tools developed, are also applicable to the alignment of the other LHCb sub-systems and the global relative alignment of the sub-detectors

Photovoltaic response around a unique180° ferroelectric domain wall in single crystalline BiFeO3

Using an experimental setup designed to scan a submicron sized light spot and collect the photogenerated current through larger electrodes, we map the photovoltaic response in ferroelectric BiFeO3 single crystals. We study the effect produced by a unique 180° ferroelectric domain wall (DW) and show that the photocurrent maps are significantly affected by its presence and shape. The effect is large in its vicinity and in the Schottky barriers at the interface with the Au electrodes, but no extra photocurrent is observed when the illuminating spot touches the DW, indicating that this particular entity is not the heart of specific photo-electric properties. Using 3D modelling, we argue that the measured effect is due to the spatial distribution of internal fields which are significantly affected by the charge of the DW due to its distortion

Negative Domain Wall Contribution to the Resistivity of Microfabricated Fe Wires

The effect of domain walls on electron transport has been investigated in microfabricated Fe wires (0.65 to 20 $\mu m$ linewidths) with controlled stripe domains. Magnetoresistance (MR) measurements as a function of domain wall density, temperature and the angle of the applied field are used to determine the low field MR contributions due to conventional sources in ferromagnetic materials and that due to the erasure of domain walls. A negative domain wall contribution to the resistivity is found. This result is discussed in light of a recent theoretical study of the effect of domain walls on quantum transport.Comment: 7 pages, 4 postscript figures and 1 jpg image (Fig. 1

Electronic control of the spin-wave damping in a magnetic insulator

It is demonstrated that the decay time of spin-wave modes existing in a magnetic insulator can be reduced or enhanced by injecting an in-plane dc current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit interaction. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of $I_\text{dc}$ in a 5~$\mu$m diameter YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope (MRFM). Complete compensation of the damping of the fundamental mode is obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.Comment: 6 pages 4 figure

Control of the spin to charge conversion using the inverse Rashba-Edelstein effect

Under the terms of the Creative Commons Attribution 3.0 Unported License to their work.We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of the spin to charge conversion in a spin pumping experiment. Using the intrinsic symmetry of the “Inverse Rashba Edelstein Effect” (IREE) in a Bi/Ag interface, the charge current changes sign when reversing the order of the Ag and Bi stacking. This confirms the IREE nature of the conversion of spin into charge in these interfaces and opens the way to tailoring the spin sensing voltage by an appropriate trilayer sequence.We would like to acknowledge financial support from the European Commission through the Marie Curie Intra European Fellowship Project No. 301656: AtomicFMR, funded by the 7th Framework Programme. This work was supported by Spanish Ministry of Economy and Competitivity through Project No. MAT2011-27553-C02, including FEDER funds, and by the Aragon Regional Government.Peer reviewe

Carbohydrate reserves in grapevine (Vitis vinifera L. 'Chasselas'): the influence of the leaf to fruit ratio

Seasonal dynamics of total non-structural carbohydrates (TNC) in relation to the leaf-fruit ratio were measured over five years at different grapevine phenological stages in one- and two-year-old canes, trunks and roots of the cultivar 'Chasselas' (Vitis vinifera L.). Carbohydrates were mainly stored as starch in different parts of the grapevine during the growing season. Soluble carbohydrates represented only a small part (< 7 % of dry weight, DW) of the TNC. In the roots and trunks, the starch content fluctuated during the growing season, reaching the lowest values between budbreak and flowering depending on the year, and the highest values between harvest and leaf fall. The soluble sugar content increased in the trunks and the two-year-old canes during the winter period with the decrease in temperatures. A negative correlation was established between the average air temperature recorded during the seven days before sample collection for carbohydrate analysis, and soluble carbohydrate content in the trunks and two-year-old canes. The leaffruit ratio (source-sink), expressed by the “light-exposed leaf area∙kg-1 fruit”, not only substantially influenced the soluble sugar content in berries but also the starch and TNC concentrations in the trunks and roots at harvest. Higher leaf-fruit ratios resulted in increased starch and TNC concentrations in the trunks and roots, which attained the maximum values when the leaf-fruit ratio neared 2.0 m2 of light-exposed leaf area∙kg-1 fruit. Canopy height and leaf area had no predominant influence on the soluble sugars, starch contents, or TNC in the permanent vine parts. 

Two New Primers Highly Specific for the Detection of Botrytis cinerea Pers. Fr.

Of thirty-nine Botrytis cinerea isolates originating in different host-plants and grown in pure cultures, twenty-six produced abundant grey aerial mycelium and sporulated intensely, whilst thirteen produced a thin mycelial layer, abundant sclerotia and secreted an unidentified yellow pigment in PDA culture media. The commonly used C729 +/– primers (5’-AGCTCGAGAGAGATCTCTGA-3’; 5’-CTGCAATGTTCTGCGTGGAA-3’) designed to detect B. cinerea did not amplify the DNA fragment of 0.73 kb in this smaller group of strains under standard conditions, whereas a shorter DNA fragment (0.60 kb) was amplified at a lower annealing temperature (50°C). This fragment was sequenced and two new internal primers were designed, BC108 + (5’-ACCCGCACCTAATTCGTCAAC-3’) and BC563 – (5’-GGGTCTTCGATACGGGAGAA-3’). These new primers were used to amplify a DNA fragment of 0.48 kb for the main group of 26 B. cinerea strains and a shorter fragment (0.36 kb) for the smaller group of 13 strains due to a deletion of 0.12 kb, which was not detected with the primers C729 +/–. All the strains were amplified to detect the presence or absence of Boty and Flipper transposable elements. No correlation was found between strains possessing the deletion and those belonging to either the vacuma or the transposa sibling species. Other closely related Botrytis species such as B. allii and B. fabae were not amplified with these primers, confirming their specificity for B. cinerea and enhancing the sensitivity of the molecular tools available to detect this fungus in host-plants