Der Einfluss von Diversifikationsstrategien auf den Aktienkurs deutscher Unternehmen

Sowohl die Diversifikation als auch die Fokussierung von Unternehmensaktivitäten werden häufig mit der Maximierung des Unternehmenswertes begründet. Wir untersuchen die Auswirkungen auf den Aktienkurs für 184 Akquisitionen sowie 139 Desinvestitionen deutscher Konzerne im Zeitraum von 1996-2005. Unternehmensdiversifikationen üben, entgegen der oft geäußerten Kritik, keinen signifikant negativen Einfluss auf den Marktwert aus. Fokussierende Unternehmensakquisitionen hingegen sind mit einem signifikanten Wertaufschlag verbunden. Der Verkauf von Unternehmensteilen führt generell zu einer Marktwertsteigerung. Dabei führen Abspaltungen außerhalb des Kerngeschäfts zu einer – allerdings insignifikant – höheren Wertsteigerung als Desinvestitionen von Kerngeschäftsaktivitäten. Statt eines systematischen Diversifikationsabschlags finden wir somit einen „Fokussierungsaufschlag“ für den deutschen Markt

First evidence of standard model pp → tttt production and performance studies of the ATLAS tile calorimeter for HL-LHC

In diesem Dokument werden zwei Analysen auf dem Gebiet der Teilchenphysik vorgestellt. Erstens, Studien über die Performanz der Rekonstruktion von Myonen unter Verwendung von Kalorimeterinformationen während der HL-LHC Phase des ATLAS Detektors. Zweitens, die Suche nach der simultanen Produktion von vier Top-Quarks, wie vom Standard Modell (SM) prognostiziert, unter Verwendung des vollständigen Run-II-Datensatzes, der von ATLAS aufgenommen wurde. Dieser Datensatz entspricht einer integrierten Luminosität von L = 139 fb-1 von Proton–Proton Kollisionen bei einer Schwerpunktsenergie von √s = 13 TeV. Für diese Arbeit wird die Performanz der Rekonstruktion von Myonen für verschiedene pile-up Szenarien untersucht, wie sie für die HL-LHC-Phase erwartet werden, und im Hinblick auf verschiedene Rauschszenarien, die den Verlust der Energieauflösung und die Verschlechterung der Detektorakzeptanz aufgrund von Alterung und Bestrahlung der Detektorkomponenten nachbilden. Diese Studie wird durchgeführt, um vorgeschlagene Szenarien für die Aufrüstung des Detektors vor ihrer Implementierung zu testen. Die Suche nach der vom SM prognostizierten Produktion von vier Top-Quarks, konzentriert sich auf die Zerfallsmoden mit zwei Leptonen gleicher Ladung oder mehr Leptonen im Endzustand. Die Suche nach diesem Prozess ist unter anderem durch die sehr hohen involvierten Energien motiviert und durch die Tatsache, dass derzeit verfügbare Datensätze möglicherweise für eine Entdeckung ausreichen. Die finalen Messergebnisse werden mit einem Profile-Likelihood-Fit erzielt, der das Ergebnis eines Boosted-Decision-Trees beinhaltet, welcher darauf trainiert ist zwischen Signal und Untergrund zu unterscheiden. Der Fit führt zu einem Wirkungsquerschnitt von σ(p→tt ¯tt ¯ )=24(+7-6)fb, was einer beobachteten (erwarteten) Signifikanz von Z = 4,3 (Z = 2,4) entspricht. Dies repräsentiert den ersten Nachweis (Evidence) für diesen Prozess. Das erhaltene Ergebnis ist mit der SM Vorhersage innerhalb von 1,7 Standardabweichungen kompatibel. Auf diesen ersten Nachweis aufbauend, wird die Möglichkeit der Rekonstruktion des vier Top-Quark Systems unter Verwendung eines kinematischen Likelihood Fits entwickelt und getestet. Die Entwicklungen und Tests werden mit dem KLFitter Software Paket durchgeführt und erzielen eine Effizienz der korrekten Zuordnung aller vier Top-Quarks von ε = 33 ± 4 % unter optimalen Bedingungen für den Endzustand mit einem Lepton.Two analyses in the field of particle physics are presented in this document. First,studies on the performance of the reconstruction of muons using calorimeter inform-ation under the conditions of the High-Luminosity Large-Hadron-Collider (HL-LHC)phase of theATLASdetector. Second, the search for the Standard Model (SM) sim-ultaneous production of four top quarks using the full Run-II data set recorded byATLAS. This data set corresponds to an integrated luminosity ofL= 139 fb−1ofproton–proton collisions at a centre of mass energy of√s= 13 TeV.Here, the performance of the reconstruction of muons is probed for different pile-upscenarios, as those expected for the HL-LHC phase, and in light of different noise scen-arios that emulate the loss of energy resolution and deterioration of detector acceptancedue to ageing and irradiation of detector components. This study is conducted to testproposed detector upgrade scenarios before their implementation.The search for SM like four top quark production presented here, focuses on the de-cay modes with two same sign or more leptons in the final state. The search for thisprocess is, among other factors, motivated by the very large energies involved and bythe fact that it is likely on the verge of being discovered with currently available datasets. The final results are obtained in a profile likelihood fit involving the outcome of aboosted decision tree trained to discriminate between signal and background. The fitresults in a production cross section ofσ(pp→tt tt) = 24+7−6fb, which correspondsto an observed (expected) significance ofZ= 4.3(Z= 2.4). This represents the firstevidence for this process. The obtained result is compatible with the SM prediction within 1.7 standard deviations.Following first evidence, the possibility of reconstructing the four top quark systemusing a kinematic likelihood approach is developed and tested. These developmentsare performed with theKLFitter tool set and yield an efficiency of correctlymatching all four top quarks of ε = 33±4 %under optimal conditions in the singlelepton final state

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Reperfusion therapy for ST elevation acute myocardial infarction 2010/2011: current status in 37 ESC countries

Aims Primary percutaneous coronary intervention (PPCI) is the preferred reperfusion therapy in ST-elevation myocardial infarction (STEMI). We conducted this study to evaluate the contemporary status on the use and type of reperfusion therapy in patients admitted with STEMI in the European Society of Cardiology (ESC) member countries. Methods and results A cross-sectional descriptive study based on aggregated country-level data on the use of reperfusion therapy in patients admitted with STEMI during 2010 or 2011. Thirty-seven ESC countries were able to provide data from existing national or regional registries. In countries where no such registries exist, data were based on best expert estimates. Data were collected on the use of STEMI reperfusion treatment and mortality, the numbers of cardiologists, and the availability of PPCI facilities in each country. Our survey provides a brief data summary of the degree of variation in reperfusion therapy across Europe. The number of PPCI procedures varied between countries, ranging from 23 to 884 per million inhabitants. Primary percutaneous coronary intervention and thrombolysis were the dominant reperfusion strategy in 33 and 4 countries, respectively. The mean population served by a single PPCI centre with a 24-h service 7 days a week ranged from 31 300 inhabitants per centre to 6 533 000 inhabitants per centre. Twenty-seven of the total 37 countries participated in a former survey from 2007, and major increases in PPCI utilization were observed in 13 of these countries. Conclusion Large variations in reperfusion treatment are still present across Europe. Countries in Eastern and Southern Europe reported that a substantial number of STEMI patients are not receiving any reperfusion therapy. Implementation of the best reperfusion therapy as recommended in the guidelines should be encourage