Technical University of Dortmund

About: Technical University of Dortmund is a education organization based out in Dortmund, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Large Hadron Collider & Neutrino. The organization has 13028 authors who have published 27666 publications receiving 615557 citations. The organization is also known as: Dortmund University & University of Dortmund.

Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube

Abstract: We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi-TeV region in the Southern sky using data from the IceCube detector. Between 2007 June and 2008 March, the partially deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 m inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic-ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the southern sky. The data include 4.3 billion muons produced by downward-going cosmic-ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of similar to 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first-harmonic amplitude of (6.4 +/- 0.2 stat. +/- 0.8 syst.) x 10(-4).

General analysis of B ¯ → K ¯ ( * ) ℓ + ℓ − decays at low recoil

Abstract: We analyze the angular distributions of $\overline{B}\ensuremath{\rightarrow}{\overline{K}}^{*}(\ensuremath{\rightarrow}\overline{K}\ensuremath{\pi}){\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ and $\overline{B}\ensuremath{\rightarrow}\overline{K}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decays in the region of low hadronic recoil in a model-independent way by taking into account the complete set of dimension-six operators $[\overline{s}\ensuremath{\Gamma}b][\overline{\ensuremath{\ell}}{\ensuremath{\Gamma}}^{\ensuremath{'}}\ensuremath{\ell}]$. We obtain several novel low-recoil observables with high sensitivity to nonstandard-model Dirac structures, including $CP$ asymmetries, which do not require flavor tagging. The transversity observables ${H}_{T}^{(1,3,4,5)}$ are found to be insensitive to hadronic matrix elements and their uncertainties even when considering the complete set of operators. In the most general scenario we show that the low recoil operator product expansion can be probed at the few-percent level using the angular observable ${J}_{7}$. Higher sensitivities are possible assuming no tensor contributions, specifically by testing the low-recoil relation $|{H}_{T}^{(1)}|=1$. We explicitly demonstrate the gain in reach of the low-recoil observables in accessing the ratio $|{\mathcal{C}}_{9}/{\mathcal{C}}_{10}|$ compared to the forward-backward asymmetry, and probing $CP$-violating right-handed currents $\mathrm{Im}{\mathcal{C}}_{{10}^{\ensuremath{'}}}$. We give updated Standard Model predictions for key observables in $\overline{B}\ensuremath{\rightarrow}{\overline{K}}^{(*)}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decays.

Predicting player churn in the wild

Abstract: Free-to-Play or “freemium” games represent a fundamental shift in the business models of the game industry, facilitated by the increasing use of online distribution platforms and the introduction of increasingly powerful mobile platforms. The ability of a game development company to analyze and derive insights from behavioral telemetry is crucial to the success of these games which rely on in-game purchases and in-game advertising to generate revenue, and for the company to remain competitive in a global marketplace. The ability to model, understand and predict future player behavior has a crucial value, allowing developers to obtain data-driven insights to inform design, development and marketing strategies. One of the key challenges is modeling and predicting player churn. This paper presents the first cross-game study of churn prediction in Free-to-Play games. Churn in games is discussed and thoroughly defined as a formal problem, aligning with industry standards. Furthermore, a range of features which are generic to games are defined and evaluated for their usefulness in predicting player churn, e.g. playtime, session length and session intervals. Using these behavioral features, combined with the individual retention model for each game in the dataset used, we develop a broadly applicable churn prediction model, which does not rely on game-design specific features. The presented classifiers are applied on a dataset covering five free-to-play games resulting in high accuracy churn prediction.

On the dynamics of electrons in an impure metal

Abstract: The inelastic scattering of the electrons of an impure metal by a screened Coulomb interaction is investigated. It is found that the rate of such an inelastic scattering is increased which can be explained by a loss of momentum conservation which in turn results from loss of translational symmetry introduced by the defects of an impure metal. Eventually, a linearised Boltzmann equation is derived for time and space dependent perturbances of the electronic distribution function. The collision integral takes into account impurity scattering as well as electron-electron and electron-phonon scattering. In an impure metal the terms corresponding to the last two processes are modified as discussed above and in a previous paper on the electron-phonon interaction.