Effects of Longitudinal Short-Distance Constraints on the Hadronic Light-by-Light Contribution to the Muon g−2g-2

We present a model-independent method to estimate the effects of short-distance constraints (SDCs) on the hadronic light-by-light contribution to the muon anomalous magnetic moment $a_\mu^\text{HLbL}$. The relevant loop integral is evaluated using multi-parameter families of interpolation functions, which satisfy by construction all constraints derived from general principles and smoothly connect the low-energy region with those where either two or all three independent photon virtualities become large. In agreement with other recent model-based analyses, we find that the SDCs and thus the infinite towers of heavy intermediate states that are responsible for saturating them have a rather small effect on $a_\mu^\text{HLbL}$. Taking as input the known ground-state pseudoscalar pole contributions, we obtain that the longitudinal SDCs increase $a_\mu^\text{HLbL}$ by $(9.1\pm 5.0) \times 10^{-11}$, where the isovector channel is responsible for $(2.6\pm 1.5) \times 10^{-11}$. More precise estimates can be obtained with our method as soon as further accurate, model-independent information about important low-energy contributions from hadronic states with masses up to 1-2 GeV become available.Comment: 19 pages, 5 figures, 1 table. Improved discussion, version accepted for publication in EPJ

Who disciples the CFO? An assessment of stakeholder power in corporate governance

We analyze the respective influence of employee and shareholder interests on the dismissal of 89 Chief Financial Officers (CFOs) of major German companies between 1999 and 2006. Drawing on stakeholder-agency theory, we argue that employees wield sufficient power to affect executive replacements. We show that the provision of job security as a proxy for employee interests has a significant effect on the likelihood of CFO dismissal. This effect is independent of the fulfillment of shareholders’ objectives. We conclude that stakeholder groups beyond shareholders exert influence on corporate governance. We argue that executives need to respond to several stakeholder groups simultaneously.Corporate Governance; Stakeholder influence; Management dismissal

Dispersion relations for hadronic light-by-light scattering in triangle kinematics

We present a new strategy for the dispersive evaluation of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon a$_{μ}$. The new approach directly applies in the kinematic limit relevant for a$_{μ}$: one of the photons is treated as an external electromagnetic field with vanishing momentum, so that the kinematics corresponds to a triangle. We derive expressions for the relevant single-particle intermediate states, as well as the tensor decompositions of the two-pion sub-processes that appear in addition to those needed in the established dispersive approach. The existing approach is based on a set of dispersion relations for the hadronic light-by-light tensor in four-point kinematics. At present it is not known how to consistently include in this framework resonant intermediate states of spin 2 or larger, due to the appearance of kinematic singularities that can be traced back to the redundancy of the tensor decomposition. We show that our new approach circumvents this problem and enables dispersion relations in the limit of triangle kinematics that are manifestly free from kinematic singularities, paving the way towards a data-driven evaluation of all relevant exclusive hadronic intermediate states

Improved Standard-Model Prediction for π^{0}→e^{+}e^{-}.

We present an improved standard-model (SM) prediction for the dilepton decay of the neutral pion. The loop amplitude is determined by the pion transition form factor for π^{0}→γ^{*}γ^{*}, for which we employ a dispersive representation that incorporates both spacelike and timelike data as well as short-distance constraints. The resulting SM branching fraction, Br[π^{0}→e^{+}e^{-}]=6.25(3)×10^{-8}, sharpens constraints on physics beyond the SM, including pseudoscalar and axial-vector mediators

Who disciples the CFO? An assessment of stakeholder power in corporate governance

We analyze the respective influence of employee and shareholder interests on the dismissal of 89 Chief Financial Officers (CFOs) of major German companies between 1999 and 2006. Drawing on stakeholder-agency theory, we argue that employees wield sufficient power to affect executive replacements. We show that the provision of job security as a proxy for employee interests has a significant effect on the likelihood of CFO dismissal. This effect is independent of the fulfillment of shareholders’ objectives. We conclude that stakeholder groups beyond shareholders exert influence on corporate governance. We argue that executives need to respond to several stakeholder groups simultaneously

Who disciples the CFO? An assessment of stakeholder power in corporate governance

We analyze the respective influence of employee and shareholder interests on the dismissal of 89 Chief Financial Officers (CFOs) of major German companies between 1999 and 2006. Drawing on stakeholder-agency theory, we argue that employees wield sufficient power to affect executive replacements. We show that the provision of job security as a proxy for employee interests has a significant effect on the likelihood of CFO dismissal. This effect is independent of the fulfillment of shareholders’ objectives. We conclude that stakeholder groups beyond shareholders exert influence on corporate governance. We argue that executives need to respond to several stakeholder groups simultaneously

PaTaS: Quality Assurance for Model-driven Software Development

The quality of software products in safety critical applications, extensively found within the space domain, is a key success factor but also a major cost driver. To ensure high quality of the software product, quality assurance processes with quality models and metrics are applied. With these tools and processes, product assurance managers and software developers are able to quantify the quality of the software under development. Within the ESA-funded study PaTaS (Product Assurance with TASTE Study), a product quality model with software and model metrics was developed and implemented in an end-to-end model-driven software development (MDSD) life cycle demonstrator. The goal of this study was to identify applicable concepts to maintain quality and dependability levels when MDSD is applied. This requires the definition of connected model and software quality indicators. These indicators were integrated into ESA’s reference software product quality model (ECSS-Q-HB-80-04A). The resulting adapted quality model got incorporated in a model-driven software development life cycle demonstrator. To evaluate this demonstrator and the integrated quality indicators in a realistic development scenario, mission-critical parts of the command and data handling subsystem of a satellite mission were modelled and subsequently coded. The aim of the activity was to demonstrate the effect of the end-to-end life cycle in combination with the developed quality model on the final onboard software product. In this paper we present the result of the study. The focus is on the quality model for MDSD and new quality metrics for models, which can be embedded in an end-to-end model-driven product development life cycle

PaTaS - Quality Assurance in Model-Driven Software Engineering for Spacecraft

Within PATAS (Product Assurance with TASTE Study), a product quality model with software and model metrics is developed and implemented in an end-to-end model-driven software engineering (MDSE) lifecycle demonstrator, based on TASTE. The goal of this study is to find applicable concepts to maintain quality and dependability levels, when MDSE is applied. This requires the definition of connected model and software quality indicators. These indicators are identified and integrated with ESA's reference software product quality model (ECSS-Q-HB-80-04A). The resulting quality model is integrated in a model-based software development lifecycle demonstrator, based on TASTE. To evaluate this demonstrator and the integrated quality indicators, mission-critical parts of the command and data handling subsystem of a satellite mission are modelled and subsequently coded, simulating a realistic development scenario as use case. The aim of the activity is to demonstrate the effect of the end-to-end lifecycle in combination with the developed quality model on the final onboard software product. The final results will set the baseline for recommendations to improve Quality Assurance in MDSE at ESA. In this talk, we present the on-going study and its latest results

The BECCAL Experiment Design and Control Software

This paper presents the software responsible for the design and execution of the experiments in the Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL) mission, an experiment with ultra-cold and condensed atoms on the International Space Station. The software consists of two parts: the experiment control software and the experiment design tools. The first corresponds to the software running on the payload and is in charge of controlling and executing the experiments, while the latter are the tools used by the scientists to create the experiment definition that will be later uploaded to the instrument to be executed. To overcome the challenge of developing software with such complexity, it was decided to follow a model-driven development approach. Several domain-specific languages (DSLs) have been created to allow scientists to describe their experiments in a domain-specific way. These descriptions are then uploaded and executed by different interpreters onboard. The paper details the architecture of the experiment control software and the different modules that compose it, as well as the developed languages and tools used to describe new experiments. The paper also discusses and evaluates some important aspects of the software, such as how resilient it is to failures, as well as the advantages and disadvantages of the selected approach compared to other approaches used in similar missions. The developed software will also be used for the MAIUS-2/3 missions

A Dual-Species Atom Interferometer Payload for Operation on Sounding Rockets

We report on the design and the construction of a sounding rocket payload capable of performing atom interferometry with Bose-Einstein condensates of 41 K and 87 Rb. The apparatus is designed to be launched in two consecutive missions with a VSB-30 sounding rocket and is qualified to withstand the expected vibrational loads of 1.8 g root-mean-square in a frequency range between 20–2000 Hz and the expected static loads during ascent and re-entry of 25 g. We present a modular design of the scientific payload comprising a physics package, a laser system, an electronics system and a battery module. A dedicated on-board software provides a largely automated process of predefined experiments. To operate the payload safely in laboratory and flight mode, a thermal control system and ground support equipment has been implemented and will be presented. The payload presented here represents a cornerstone for future applications of matter wave interferometry with ultracold atoms on satellites