Anomalous decay and scattering processes of the eta meson

We amend a recent dispersive analysis of the anomalous $\eta$ decay process $\eta\to\pi^+\pi^-\gamma$ by the effects of the $a_2$ tensor meson, the lowest-lying resonance that can contribute in the $\pi\eta$ system. While the net effects on the measured decay spectrum are small, they may be more pronounced for the analogous $\eta'$ decay. There are nonnegligible consequences for the $\eta$ transition form factor, which is an important quantity for the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment. We predict total and differential cross sections, as well as a marked forward-backward asymmetry, for the crossed process $\gamma\pi^-\to\pi^-\eta$ that could be measured in Primakoff reactions in the future.Comment: 12 pages, 11 figures; v2 matches version published in EPJ

Sharing Economy or Skimming Economy? A Review on the Sharing Economy\u27s Impact

During the last years, the Sharing Economy with its prominent trailblazers like Airbnb and Uber has become ubiquitous in our daily lives, enabling us to enjoy new and less expensive means of transportation, accommodation, and other goods and services. With the increasing success comes an increasing headwind from the media, unions, and legislators, claiming negative impacts like precarious employment situations or the promotion of tax evasion. These circumstances provide an uncertain environment for researchers or practitioners developing new sharing services. Conducting a systematic literature review, a comprehensive overview of claimed positive and negative impacts of the Sharing Economy is given. Based on this overview, guidelines are derived that are supposed to help address these issues during the development of the new sharing services and underlying information systems

"Letztes Halbjahr stand ich zwei" : Zur Akkuratheit selbst berichteter Noten

Pädagogisch-psychologische Studien verwenden oft die von Schülern selbst berichteten Noten als Leistungsindikatoren. In der vorliegenden Studie wurde die Akkuratheit dieser Selbstangaben überprüft, indem selbst berichtete Mathematiknoten der letzten Klassenarbeit und des letzten Zeugnisses mit den Lehrerangaben verglichen wurden. Es zeigen sich hohe Korrelationen, allerdings wurden die Noten im Mittel überschätzt. Die Akkuratheit der Selbsteinschätzung ist praktisch unabhängig von Geschlecht, mathematischem Fähigkeitsselbstkonzept und mathematischer Leistung (erfasst über Items aus dem TIMSS-Instrumentarium)

Asymptotic expansions through the loop-tree duality

First results towards a general method for asymptotic expansions of Feynman amplitudes in the loop-tree duality (LTD) formalism are presented. The asymptotic expansion takes place at integrand-level in the Euclidean space of the loop three-momentum, where the hierarchies among internal and external scales are well-defined. Additionally, the UV behaviour of the individual contributions to the asymptotic expansion emerges only in the first terms of the expansion and is renormalized locally in four space-time dimensions. These two properties represent an advantage over the method of Expansion by Regions (EbR). We explore different approaches in different kinematical limits, and derive general guidelines with several benchmark examples.Comment: 23 pages, 7 figure

Vorhersage von Fähigkeitsselbstkonzepten : Zur Bedeutung von Einzel- und Klassenleistung

In der vorliegenden Arbeit wird der Big-Fish-Little-Pond Effect (BFLPE) untersucht, welcher das Phänomen beschreibt, dass sich bei Schülern die mittlere Klassenleistung bei Konstanthaltung der individuellen Leistung negativ auf das Fähigkeitsselbstkonzept auf Individualebene auswirkt. Es wird weiterhin angenommen, dass die soziale Bezugsnormorientierung der Lehrkraft als Moderatorvariable den BFLPE verstärkt. Lehrer mit einer hohen sozialen Bezugsnormorientierung sollen demnach bei Leistungsbewertungen stärker die Leistung der Klassenkameraden berücksichtigen, was ungünstige soziale Vergleiche akzentuiert und den BFLPE letztendlich erhöht. Diese Annahmen wurden anhand von Daten überprüft, die an 866 Siebt- und Achtklässler aus 36 unterschiedlichen Klassen sechs verschiedener Schulen erhoben wurden. Mittels Mehrebenenanalysen wurde der Einfluss der Prädiktoren Mathematikleistung auf Individual- und Klassenebene, die aus Aufgaben der dritten internationalen Mathematik- und Naturwissenschaftsstudie (TIMSS) erfasst wurde, sowie perzipierte soziale Bezugsnormorientierung des Lehrers auf die differenziert erhobenen mathematischen Fähigkeitsselbstkonzepte (absolut, kriterial, sozial, individuell), berechnet. Dabei zeigte sich, dass die Leistung auf Individualebene einen positiven Effekt auf die Fähigkeitsselbstkonzepte hat. Demgegenüber war die auf Klassenebene aggregierte Leistung ein negativer Prädiktor für die akademischen Selbstkonzepte, was eine Replikation des BFLPE darstellt. Entgegen der Annahmen verringerte die soziale Bezugsnormorientierung des Lehrers den BFLPE jedoch nicht. Implikationen für die Praxis und weitere Forschungen werden diskutiert

Asymptotic expansions and causal representations through the loop-tree duality

Large-scale particle physics experiments have provided a vast amount of high-quality data during the last decades. A leading role has been played by the Large Hadron Collider where the evaluation and analysis of its second run is currently still in progress while the third run is about to start, promising ever higher precision data of particle collisions and subsequent decays. The agreement between experimental observations and theoretical predictions using the Standard Model of Particle Physics is excellent. Indeed, this is a problem since there are currently few clues for how genuine shortcomings of the model can be overcome. New physics phenomena can appear either at higher energies, which would require the construction of an even larger particle collider, or as small deviations accessible only through precision calculations. These involve higher-order quantum corrections which pose technical challenges. An alternative to the traditional method has been proposed in the form of the loop-tree duality theorem. A derivation of the theorem based on the application of the Cauchy residue theorem is presented and the application of the loop-tree duality to the two loop sunrise amplitude is demonstrated in detail. Further, the appearance of singularities in the dual integrands is analyzed. Cancellations between unphysical singularities are demonstrated. In this work a newly found purely causal representation of the dual integrands and the definitions of several classes of multiloop topologies as well as their loop-tree duality representations are presented. The main part of this work is focused on the development of a framework for using asymptotic expansions in the context of the loop-tree duality. Previously found expansions in the leading order Higgs boson decay are analyzed and their limitations pointed out. A general method is derived for defining asymptotic expansions of scattering amplitudes within the loop-tree duality framework. This method involves the expansion of the dual propagator in a general form that is easily applicable to any given kinematic limit. This expanded propagator is used in the calculation of the scalar two-point function. Upon integration a master expansion is obtained, which can be evaluated for a variety of kinematic limits. Convergence is obtained both at the level of the integrand as well as for the integrated result. The tested limits are: one large mass, a large external momentum, and the threshold limit (both below and above threshold). A separate method for expanding the dual integrand is derived by dividing the integration range into two dual regions such that the integrand can be expanded separately using a Taylor series. This method takes direct advantage of the Euclidean nature of the dual integrand. It has been successful for the scalar two-point function. In the following, the method is applied to the scalar three-point function and tested for two different limits. A multiloop expansion has been achieved for the case of the maximal-loop-topology. Finally, an application to a physical amplitude is shown: the process q q -> H g, which is one of the amplitudes contributing to highly boosted Higgs boson production. Also for this process one limit below and one above threshold were tested successfully

Advantages and pitfalls of machine translation for party research: the translation of party manifestos of European parties using DeepL

Parties are the central actors in representative democracies as they perform important democratic functions. Thus, the identification of party positions is a crucial concern. Party researchers mainly rely on party manifestos to estimate policy positions. However, the analysis of manifestos is accompanied by challenges—one of the biggest being cross-national comparisons because of different institutional settings and languages. This article discusses machine translation (MT) as a new option for party research, and reports on the author's experiences with the translation of more than 200 party manifestos using the commercial artificial intelligence (AI) translation tool DeepL. To make this approach widely applicable, the (technical) procedure, including its problems and workarounds for large-scale projects, is presented as a step-by-step guide using R. Additionally, drawing on the most recent German, Estonian, Italian and Polish parliamentary election manifestos this article evaluates the quality of the DeepL translations by applying both back translation and Wordfish analyses. The main findings indicate that DeepL offers high-quality translations as more than 90% of the checked sentences are reproduced word-for-word or at least synonymously and with stable positioning on the left-right scale of both original and English translation. The results have greater implications for political science research as they speak to the reliability of machine translation for political texts

Towards an improved understanding of eta --> gamma^* gamma^*

We argue that high-quality data on the reaction $e^+e^-\to \pi^+\pi^-\eta$ will allow one to determine the double off-shell form factor $\eta \to \gamma^*\gamma^*$ in a model-independent way with controlled accuracy. This is an important step towards a reliable evaluation of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. When analyzing the existing data for $e^+e^- \to \pi^+\pi^-\eta$ in the range of total energies $1\text{GeV}^2<Q_2^2<(4.5\text{GeV})^2$, we demonstrate that the double off-shell form factor $F_{\eta\gamma^*\gamma^*}(Q_1^2,Q_2^2)$ is consistent with the commonly employed factorization ansatz at least for $Q_1^2<1\text{GeV}^2$, if the effect of the $a_2$ meson is taken into account. However, better data are needed to draw firm conclusions.Comment: 7 pages, 3 figure

REPAINTING THE BUSINESS MODEL CANVAS FOR PEER-TO-PEER SHARING AND COLLABORATIVE CONSUMPTION

Sharing Economy businesses have become very popular recently but there is little guidance available on how to develop the respective business models. We faced this problem during a consortium research project for developing a service for electric vehicle charging that adopts the paradigm of Peer-to-Peer Sharing and Collaborative Consumption (P2P SCC)—a specific branch of the Sharing Economy. We use Action Design Research (ADR) to develop an adapted version of the Business Model Canvas that is specifically tailored to the needs of P2P SCC business model development. The adapted canvas is then applied to develop a business model for the proposed service. The learnings from the development process are formalized into a set of generally applicable guidelines for the development of P2P SCC business models. The resulting guidelines and the adapted canvas provide guidance for both researchers and practitioners who want to either develop new or analyze existing P2P SCC business models

Testing Technical Feasibility in CPS Development Projects

Cyber-physical systems (CPSs) are service systems that connect a product’s physical and computational elements through telecommunication networks. Typically, the processes in CPSs are executed on this physical and computational infrastructure. As the developing of new CPS is costly, testing and validating a CPS’s design at an early stage of development is desirable to avoid bad investments. The high development and potentially high hardware costs, however, make it difficult to create a full CPS prototype only for testing. This work uses Trkman’s critical success factors of business process management (BPM) as a theoretical lens and identifies “technical-feasibility fit” as an additional complementary success factor. Based on these factors, we develop a method for creating CPS testbeds that allow testing of CPSs at lower costs at an early stage of the development. We demonstrate the method’s application by a case in which we develop a testbed for an electric vehicle charging service