The ATLAS b-Jet Trigger

The online event selection is crucial to reject most of the events containing uninteresting background collisions while preserving as much as possible the interesting physical signals. The b-jet selection is part of the trigger strategy of the ATLAS experiment and a set of dedicated triggers was contributing to the event selection for the 2011 running. The b-jets acceptance is increased and the background reduced by lowering jet transverse energy thresholds at the first trigger level and applying b-tagging techniques at the subsequent levels. Different physics channels, especially topologies containing more than one b-jet where higher rejection factors are achieved, benefit from using the b-jet trigger. An overview of the b-jet trigger menu and performance on data is presented.Comment: 4 pages, 6 figures, conference proceedings for PIC201

The Heavy Photon Search Experiment

Interest in new physics models including so-called hidden sectors has increased in recent years as a result of anomalies from astrophysical observations. The Heavy Photon Search (HPS) experiment proposed at Jefferson Lab will look for a mediator of a new force, a GeV-scale massive U(1) vector boson, the Heavy Photon, which acquires a weak coupling to electrically charged matter through kinetic mixing. The HPS detector, a large acceptance forward spectrometer based on a dipole magnet, consists of a silicon tracker-vertexer, a lead-tungstate electromagnetic calorimeter, and a muon detector. HPS will search for the e+e- or mu+mu- decay of the Heavy Photon produced in the interaction of high energy electrons with a high Z target, possibly with a displaced decay vertex. In this article, the description of the detector and its sensitivity are presented.Comment: 4 pages, 4 figures, contributed to the 8th Patras Workshop on Axions, WIMPs and WISPs, Chicago, July 18-22, 201

The Ghost in the Courtroom: When Opinions Are Adopted Verbatim from Prosecutors

Judicial opinions captivate the legal community, serving as a hub for teaching new lawyers and developing the law. These opinions also provide a method for the justice system to communicate with the people it serves—both the parties to the cases and the public. This communication should be well-reasoned and developed from a neutral standpoint. However, this ideal is being seriously threatened by ghostwriting, the practice of allowing a party to write the opinion. This is particularly troubling in criminal cases, where the very lawyers charged with prosecuting defendants are writing the opinions against them. This Note proposes that opinions written by prosecutors should be subject to de novo appellate review. Additionally, states should pass legislation and revise ethics rules to require that judges critically review a proposed opinion, refrain from adopting it verbatim, give the opposing party an opportunity to reply, and write an original legal analysis section. Change is necessary to ensure that opinions are not just a recitation of a prosecutor’s argument, but a thoughtful product of an impartial judge. Left unchecked, ghostwriting will destroy the value of opinions and undermine the integrity of adjudication

First determination of the electric charge of the top quark

In this thesis, the first determination of the electric charge of the top quark is presented using 370pb-1 of data recorded by the D0 detector at the Fermilab Tevatron accelerator. ttbar events are selected with one isolated electron or muon and at least four jets out of which two are b-tagged by reconstruction of a secondary decay vertex (SVT). The method is based on the discrimination between b- and bbar-quark jets using a jet charge algorithm applied to SVT-tagged jets. A method to calibrate the jet charge algorithm with data is developed. A constrained kinematic fit is performed to associate the W bosons to the correct b-quark jets in the event and extract the top quark electric charge. The data is in good agreement with the Standard Model top quark electric charge of 2e/3. The scenario where the selected sample is solely composed of an exotic quark Q with charge 4e/3 is excluded at 92% confidence level. Using a Bayesian approach, an upper limit on the fraction of exotic quarks rho < 0.80 at 90% confidence level is obtained.Comment: Lic. thesis, Royal Institute of Technology, KTH, November 200

Business Survey Data: Do They Help in Forecasting the Macro Economy?

In this paper we examine whether data from business tendency surveys are useful for forecasting the macro economy in the short run. Our analyses primarily concern the growth rates of real GDP but we also evaluate forecasts of other variables such as unemployment, price and wage inflation, interest rates, and exchange-rate changes. The starting point is a so-called dynamic factor model (DFM), which is used both as a framework for dimension reduction in forecasting and as a procedure for filtering out unimportant idiosyncratic noise in the underlying survey data. In this way, it is possible to model a rather large number of noise-reduced survey variables in a parsimoniously parameterised vector autoregression (VAR). To assess the forecasting performance of the procedure, comparisons are made with VARs that either use the survey variables directly, are based on macro variables only, or use other popular summary indices of economic activity. As concerns forecasts of GDP growth, the procedure turns out to outperform the competing alternatives in most cases. For the other macro variables, the evidence is more mixed, suggesting in particular that there often is little difference between the DFM-based indicators and the popular summary indices of economic activity.Business survey data; Dynamic factor models; Macroeconomic forecasting

Business Survey Data: Do They Help in Forecasting the Macro Economy?

In this paper we examine whether data from business tendency surveys are useful for forecasting the macro economy in the short run. Our analyses primarily concern the growth rates of real GDP but we also evaluate forecasts of other variables such as unemployment, price and wage inflation, interest rates, and exchange-rate changes. The starting point is a so-called dynamic factor model (DFM), which is used both as a framework for dimension reduction in forecasting and as a procedure for filtering out unimportant idiosyncratic noise in the underlying survey data. In this way, it is possible to model a rather large number of noise-reduced survey variables in a parsimoniously parameterised vector autoregression (VAR). To assess the forecasting performance of the procedure, comparisons are made with VARs that either use the survey variables directly, are based on macro variables only, or use other popular summary indices of economic activity. As concerns forecasts of GDP growth, the procedure turns out to outperform the competing alternatives in most cases. For the other macro variables, the evidence is more mixed, suggesting in particular that there often is little difference between the DFM-based indicators and the popular summary indices of economic activity

Effects of Voids in Tensile Single-Crystal Cu Nanobeams

Molecular dynamic simulations of defect nanosized beams of single-crystal Cu, loaded in displacement controlled tension until rupture, have been performed. The defects are square-shaped, through-the-thickness voids of different sizes, placed centrally in the beams. Three different cross section sizes and two different crystallographic orientations are investigated. As expected, the sizes of the beam cross section and the void as well as the crystal orientation strongly influence both the elastic and the plastic behaviors of the beams. It was seen that the strain at plastic initiation increases with beam cross section size as well as with decreasing void size. It is further observed that the void deformed in different ways depending on cross section and void size. Sometimes void closure, leading to necking of the beam cross section followed by rupture occurred. In other cases, the void elongated leading to that the two ligaments above and below the void ruptured independently

Arbetsmaskiners bidrag till luftföroreningar i tätorter

The Swedish government has decided an action plan against particulate matter (PM10) within the county of Stockholm. Among other thing, the action plan stipulate that measures shall be taken in order to increase the knowledge about emissions of PM10 from non-road mobile machinery and their contribution to the air quality within densely populated areas. Non-road mobile machinery are characterised as mobile machinery not intended for the use of passenger- or goods-transport on the road, and equipped with an internal combustion engine as specified in directive 97/68/EC and directive 2000/25/EC, i.e. agricultural and forestry tractors and construction equipment such as wheel loaders, excavators, articulated haulers and mobile cranes. The purpose of this project, which was financed by the Swedish national road administration, was to update and summarise the current knowledge concerning fuel consumption and emissions from non-road mobile machinery and their contribution to the air quality in densely populated areas. A more specific aim of the project was to estimate the occurrence and age distribution and annual work hours of non-road mobile machinery within densely populated areas. Furthermore, annual fuel consumption and emissions amounts were also derived. Usually a single emission factor for each pollutant has been used when estimating emissions from the entire non-road mobile machinery sector, which has resulted in fairly uncertain results. Previous research has shown that it is not possible to develop one single set of emission factors that gives representative results for all types of non-road mobile machinery and operations (Hansson et al., 2001; Starr et al., 1999; Ullman et al., 1999). The latest research within the EMMA-projects in Sweden about the presence, use and emissions from non-road mobile machinery has resulted in better knowledge and data concerning emissions from non-road mobile machinery. Within the present project, emissions from non-road mobile machinery in two densely populated areas or population centres with different sizes have been studied. One large population centre represented by the city of Stockholm and one small represented by the town of Ljungby. The calculation of fuel consumption and emissions from non-road mobile machinery within the city of Stockholm has been conducted in accordance with the advanced approach presented by the emission inventory guidebook from the European Environement Agency (EEA, 2005). However, the methodology has been modified in order to thoroughly represent the actual assembly of non-road mobile machinery including the work performed by those machines annually. The same model that was used to derive fuel consumption has been employed for emissions as well. Compared with using average information, more reliable data were obtained through describing the number of machines, annual hour, engine power, load factor, specific fuel consumption and emissions amounts for each type of non-road mobile machinery and model year. All data were stored and used in different matrices, one for each variable. In total 31 different types of machines were defined for which data were collected for all model years from 1982 to 2006. Extensive inventories of non-road mobile machinery were carried out for both the city of Stockholm and Ljungby. For Stockholm the inventory contained both number of units and annual work hour as function of the age of the machinery. Reliable data could be obtained through the Swedish Machinery Testing Institute’s accredited inspection database in combination with statistics over both annual sale returns and registered machinery from the national vehicle database. The results from the inventory showed that about 2 800 non-road mobile machinery with both varying age and annual work hours operated within the city of Stockholm. In the city of Ljungby, less than 100 non-road mobile machinery were estimated to operate, thus called for an alternative method for the inventory. Based on data from local contractors that operated in the city of Ljungby, annual work hour for different types of non-road mobile machinery were collected. The result showed that about 48 000 hours of work with non-road mobile machinery were carried out within the city of Ljungby annually. Moreover, the majority of the work were performed with wheel loaders and different types of excavators. In table S1 annual emission- and fuel consumption amounts from the non-road mobile machinery sector in the cities of Stockholm and Ljungby year 2006 are shown

Time-dependent climate impact of beef production - can carbon sequestration in soil offset enteric methane emissions?

The time-dependent climate impact of beef production, including changes in soil organic carbon, was examined in this study. A hypothetical suckler cow system located in south-east Sweden was analysed using a time dependent life cycle assessment method in which yearly fluxes of greenhouse gases were considered and the climate impact in terms of temperature response over time was calculated. The climate impact expressed as carbon dioxide equivalents, i.e. global warming potential in a 100-year time perspective, was also calculated. The Introductory Carbon Balance Model was used for modelling yearly soil organic carbon changes from land use. The results showed an average carbon sequestration rate of 0.2 Mg C ha(-1) and yr(-1), so carbon sequestration could potentially counteract 15-22% of emissions arising from beef production (enteric fermentation, feed production and manure management), depending on system boundaries and production intensity. The temperature response, which showed a high initial increase due to methane emissions from enteric fermentation, started to level off after around 50 years due to the short atmospheric lifetime of methane. However, sustained production and associated methane emissions would maintain the temperature response and contribute to climate damage. A forage-grain beef system resulted in a lower climate impact than a forage-only beef system (due to higher slaughter age), even though more carbon was sequestered in the forage-only system