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.

The Role of Electronic and Phononic Excitation in the Optical Response of Monolayer WS2 after Ultrafast Excitation

Abstract: Transient changes of the optical response of WS2 monolayers are studied by femtosecond broadband pump–probe spectroscopy. Time-dependent absorption spectra are analyzed by tracking the line width broadening, bleaching, and energy shift of the main exciton resonance as a function of time delay after the excitation. Two main sources for the pump-induced changes of the optical response are identified. Specifically, we find an interplay between modifications induced by many-body interactions from photoexcited carriers and by the subsequent transfer of the excitation to the phonon system followed by cooling of the material through the heat transfer to the substrate.

The benefits of \bar{B} \to {\bar{K}^*}{l^{+} }{l^{-} } decays at low recoil

Abstract: Using the heavy quark effective theory framework put forward by Grinstein and Pirjol we work out predictions for $ \bar{B} \to {\bar{K}^*}{l^{+} }{l^{-} } $ , l = e, μ, decays for a softly recoiling $ {\bar{K}^*} $ , i.e., for large dilepton masses $ \sqrt {{{q^2}}} $ of the order of the b-quark mass m b . We work to lowest order in Λ/Q, where $ Q = \left( {{m_b}\sqrt {{{q^2}}} } \right) $ and include the next-to-leading order corrections from the charm quark mass m c and the strong coupling at $ \mathcal{O}\left( {{{{m_c^2}} \left/ {{{Q^2},{\alpha_s}}} \right.}} \right) $ . The leading Λ/m b corrections are parametrically suppressed. The improved Isgur-Wise form factor relations correlate the $ \bar{B} \to {\bar{K}^*}{l^{+} }{l^{-} } $ transversity amplitudes, which simplifies the description of the various decay observables and provides opportunities for the extraction of the electroweak short distance couplings. We propose new angular observables which have very small hadronic uncertainties. We exploit existing data on $ \bar{B} \to {\bar{K}^*}{l^{+} }{l^{-} } $ distributions and show that the low recoil region provides powerful additional information to the large recoil one. We find disjoint best-fit solutions, which include the Standard Model, but also beyond-the-Standard Model ones. This ambiguity can be accessed with future precision measurements.

Attribute coupled grammars

Abstract: In this paper, attribute grammars are viewed as specifying translations from source language terms into target language terms. The terms are constructed over a hierarchical signature consisting of a semantic and a syntactic part. Attribute grammars are redefined to become morphisms in the category of such signatures, called attribute coupled grammars, such that they come with an associative composition operation. The composition allows for a new kind of modularity in compiler specifications. The paper also discusses properties of the concept with respect to attribute evaluation and application as a tree transformation device.