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- Aad, G., et al.
(författare)
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Readiness of the ATLAS Tile Calorimeter for LHC collisions
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:4, s. 1193-1236
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Tidskriftsartikel (refereegranskat)abstract
- The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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- Aad, G, et al.
(författare)
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Search for Higgs Boson Pair Production in the γγbb[over ¯] Final State Using pp Collision Data at sqrt[s]=8 TeV from the ATLAS Detector.
- 2015
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Ingår i: Physical Review Letters. - 1079-7114. ; 114:8
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Tidskriftsartikel (refereegranskat)abstract
- Searches are performed for resonant and nonresonant Higgs boson pair production in the γγbb[over ¯] final state using 20 fb^{-1} of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X→hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.
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| 41. |
- Aad, G., et al.
(författare)
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Studies of the performance of the ATLAS detector using cosmic-ray muons
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:3
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Tidskriftsartikel (refereegranskat)abstract
- Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
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| 42. |
- Aad, G., et al.
(författare)
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The ATLAS Inner Detector commissioning and calibration
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 787-821
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 mu m and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.
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| 43. |
- Aad, G., et al.
(författare)
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The ATLAS Simulation Infrastructure
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 823-874
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Tidskriftsartikel (refereegranskat)abstract
- The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.
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| 45. |
- Elmquist, Marie
(författare)
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Measurement and source apportionment of ubiquitous soot black carbon in sediments
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The pyrogenic particles formed from incomplete combustion of organic matter are often termed black carbon (BC) and they partake in many important biogeochemical processes. For instance, BC in water and sediment affects the solid-water partitioning of hydrophobic organic pollutants reducing their bioavailability.The key objective of this thesis was to test the chemothermal oxidation method (CTO) to quantify soot-BC in sediments. In the CTO method, sedimentary BC is isolated by removing non-pyrogenic organic matter through thermal combustion at 375°C under active airflow and subsequent removal of inorganic carbonates by adding hydrochloric acid. The CTO method was here shown to work well for quantifying the thermally more stable soot-BC phase.Another objective was to study sediment samples to measure the historical and spatial distribution of combustion products. First, historical fluxes of BC and polycyclic aromatic hydrocarbons (PAH) were investigated in a Swedish lake sediment. Increasing fluxes of BC and PAH were seen in sediment dated to the industrial revolution in the 1850s, the high coal usage in the early 1900s lead to a 5 time increase in BC flux relative to the pre-industrial flux, and the switch from coal to oil usage in the 1950s lead to a 46 time increase in PAH flux relative to the pre-industrial flux. Further, lower fluxes came from stricter emission controls in the 1960s, improvements in combustion technology and the usage of catalytic filters from mid-1980s. Modern sediment measured 20% lower BC flux and 5 times higher PAH flux relative to the pre-industrial fluxes.Secondly, the spatial distribution and sources of sedimentary soot-BC were studied in rivers in the Arctic region. The estimated BC flux was highest in the McKenzie (99 kton yr-1) whereas it was lowest in Yukon (1.1 kton yr-1). Contemporary biomass-derived BC was detected for the Yenisey, whereas fossil fuel derived BC was found for the Lena, Yukon and McKenzie.
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| 46. |
- Gottselig, N., et al.
(författare)
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Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers
- 2017
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 31:10, s. 1592-1607
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Tidskriftsartikel (refereegranskat)abstract
- Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (~1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 ± 5% (Si) and 53 ± 21% (Fe; mean ± SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe- to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.
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| 47. |
- Kruse, Jens, et al.
(författare)
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Innovative methods in soil phosphorus research: A review
- 2015
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Ingår i: Journal of Plant Nutrition And Soil Science/Zeitschrift für Pflanzenernahrung und Bodenkunde. - : Wiley-VCH Verlagsgesellschaft. - 1436-8730 .- 1522-2624. ; 178:1, s. 43-88
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade,concerns about the future of its global supply have stimulated much research on soil P and meth-od development. This review provides an overview of advanced state-of-the-art methods cur-rently used in soil P research. These involve bulk and spatially resolved spectroscopic and spec-trometric P speciation methods (1 and 2D NMR, IR, Raman, Q-TOF MS/MS, high resolution-MS,NanoSIMS, XRF, XPS, (m)XAS) as well as methods for assessing soil P reactions (sorption iso-therms, quantum-chemical modeling, microbial biomass P, enzymes activity, DGT,33P isotopicexchange,18O isotope ratios). Required experimental set-ups and the potentials and limitationsof individual methods present a guide for the selection of most suitable methods or combina-tions
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| 48. |
- Ladd, Brenton, et al.
(författare)
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Carbon isotopic signatures of soil organic matter correlate with leaf area index across woody biomes
- 2014
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 102:6, s. 1606-1611
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Tidskriftsartikel (refereegranskat)abstract
- Leaf area index (LAI), a measure of canopy density, is a key variable for modelling and understanding primary productivity, and also water use and energy exchange in forest ecosystems. However, LAI varies considerably with phenology and disturbance patterns, so alternative approaches to quantifying stand-level processes should be considered. The carbon isotope composition of soil organic matter (C-13(SOM)) provides a time-integrated, productivity-weighted measure of physiological and stand-level processes, reflecting biomass deposition from seasonal to decadal time scales.Our primary aim was to explore how well LAI correlates with C-13(SOM) across biomes.Using a global data set spanning large environmental gradients in tropical, temperate and boreal forest and woodland, we assess the strength of the correlation between LAI and C-13(SOM); we also assess climatic variables derived from the WorldClim database.We found that LAI was strongly correlated with C-13(SOM), but was also correlated with Mean Temperature of the Wettest Quarter, Mean Precipitation of Warmest Quarter and Annual Solar Radiation across and within biomes.Synthesis. Our results demonstrate that C-13(SOM) values can provide spatially explicit estimates of leaf area index (LAI) and could therefore serve as a surrogate for productivity and water use. While C-13(SOM) has traditionally been used to reconstruct the relative abundance of C-3 versus C-4 species, the results of this study demonstrate that within stable C-3- or C-4-dominated biomes, C-13(SOM) can provide additional insights. The fact that LAI is strongly correlated to C-13(SOM) may allow for a more nuanced interpretation of ecosystem properties of palaeoecosystems based on palaeosol C-13 values.
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| 49. |
- Roth, Philipp J., et al.
(författare)
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Differentiation of charcoal, soot and diagenetic carbon in soil : method comparison and perspectives
- 2012
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Ingår i: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 46, s. 66-75
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Tidskriftsartikel (refereegranskat)abstract
- The various sources of pyrogenic and coalified carbon (black carbon, BC) in soil have considerable structural heterogeneity, making the quantification of BC a challenge. This study was aimed at evaluating the capability of different detection procedures to recover different types of BC from soil. We added defined quantities of urban dust (UD, NIST SRM1649a), diesel particulate matter (DPM, NIST SRM2975), charcoal, lignite, bituminous coal and wood to four topsoil samples. Mixtures were analyzed by way of chemothermal oxidation (CTO), thermal gradient oxidation (ThG), the benzene polycarboxylic acid method (BPCA) and mid-infrared spectroscopy (MIRS). CTO returned good quantification of soot BC in the pure DPM, yet the recovery of soot BC from soil was unsatisfactory (18-270%). ThG gave good precision but lower values for pure soot BC. It severely overestimated the BC content for all soil-standard mixtures. The BPCA method gave a low return for soot BC, but for the spiked soil it reliably detected charcoal and coalified C (69-107% avg. recovery) but underestimated soot BC (52-90% recovery of DPM). Linear coherence in specific MIR vibrations was found in one component soil-BC mixtures for each BC type. Applying these standard calibrations to multi-component mixtures allowed detecting charcoal and a quantification of soot BC (88% avg. recovery) via MIRS, but ignored the presence of diagenetic C. We see the greatest potential in differentiating soot from charcoal in soil by employing a combination of chemical and thermal oxidation and MIRS, while the differentiation from diagenetic C is not possible yet.
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| 50. |
- Wang, Fang, et al.
(författare)
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Emerging contaminants: A One Health perspective
- 2024
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Ingår i: Innovation. - 2666-6758. ; 5
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Forskningsöversikt (refereegranskat)abstract
- Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.
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