On the Applicability of the Weak Coupling Expansion for Time-Moments of Heavy Quark Correlators

Die Simulation von diskretisier QCD hat sich zu einem sehr erfolgreichen Verfahren entwickelt, um nicht-perturbativen Berechnungen durchzuführen. In dieser Arbeit untersuchen wir im Detail die Zeit-Momente schwerer Quark-Korrelatoren mit hoher Präzision. Diese werden verwendet, um die QCD-Kopplung durch den Vergleich von Gitter- und Störungsberechnungen zu extrahieren. Dabei müssen diese Observablen von Energien dominiert werden, bei denen beide Methoden angewendbar sind. Genaue Abschätzungen der systematischen Unsicherheiten ist notewendig, da dies Auswirkungen auf Berechnungen von, z.B., Higgs-Zerfällen zu b-Quarks oder Gluonen und Z-Bosonen-Partialbreiten haben. Wir führen eine quenched Untersuchung der Zeitmomente durch, um im großen Volumen mit L=2fm und T=6fm mit offenen Randbedingungen, Gitterabständen von bis ca. 0.01 fm zu erreichen. Wir berechnen Momente und dabei die Kopplung und den Trunkierungsfehler für wechselnde Energie von 0.8 bis 3.5 Mal die charm Masse. Um die großen Diskretisierungseffekte zu kontrollieren, verwenden wir ein nicht-perturbativ verbessertes Wilson-Clover-Fermionen-Dublett mit einem twisted mass Term. Neben der Kopplung untersuchen wir auch ihren Verlauf bis zur unendlichen Energie, kodiert im Lambda-Parameter, und die darin enthaltenen Trunkierungsfehler. Der extrahierte Lambda-Parameter bei Energieskalen von 2 Mal die Charmmasse weist, in Bezug auf step-scaling Ergebnisse, Abweichungen in der Größenordnung von 5% bis 10% auf. Eine Extrapolation bis zum Nullwert der Kopplung ist möglich, allerdings mit einer beträchtlichen Steigung. Weitverbreitete Variationen der perturbativen Renormierungsskala zur Abschätzung des Trunkierungsfehlers scheinen hier die tatsächliche Größe der Fehler zu unterschätzen. Bei der Verwendung der Störungstheorie hoher Ordnung auf den Skalen der Flavor-Physik für die Momente der Korrelatoren schwerer Quarks ist Vorsicht geboten, da große Trunkierungsfehler auftreten können.The simulation of discretized QCD has become a very successful method to perform non-perturbative calculations. In this work we study in detail the time-moments of heavy quark correlators with high precision. These are used to extract the QCD coupling by comparing lattice and perturbative calculations. These observables must be dominated by energies at which both methods are applicable. Accurate estimates of the systematic uncertainties are needed as this has implications for calculations of, e.g., Higgs decays to b-quarks or gluons and Z-boson partial widths. We carry out a quenched investigation of the time-moments in order to achieve lattice spacings of down to approx. 0.01 fm in large volume, L=2fm and T=6fm, with open boundary conditions. We calculate moments and thereby the coupling and the truncation error for varying energy from 0.8 to 3.5 times the charm mass. To control the large discretization effects, we use a non-perturbatively enhanced Wilson-Clover fermion doublet with a twisted mass term. In addition to the coupling, we also study its evolution to infinite energy, encoded in the lambda parameter, and the truncation errors therein. The extracted lambda parameter at energy scales of 2 times the charm mass shows deviations in the order of 5% to 10% with respect to step-scaling results. Extrapolation to the zero value of the coupling is possible, but with a considerable slope. Widespread variations of the perturbative renormalization scale to estimate the truncation error seem to underestimate the actual size of the errors here. Care should be taken when using high-order perturbation theory on the scales of flavor physics for the moments of heavy quark correlators, as large truncation errors can occur

Designing Psychological Co-research of Emancipatory-Technical Relevance Across Age Thresholds

The requirement that theoretical and empirical research is to sustainably benefit not only the nominal researcher, but also the other research participants, is deeply embedded in the conceptual-analytical framework of Psychology from the Standpoint of the Subject (PSS) and its co-researcher principle. PSS research is thus to be of emancipatory relevance to those others the researcher comes to collaborate with. Meanwhile, the question of how this requirement can be prospectively integrated into the design of a research project remains subject to debate. This question emerges as particularly difficult to tackle in research projects that engage in co-research with young children: How can a researcher ensure that the young children s-he works togethe with benefit from the research project? Based on the critical analysis of an earlier research project implemented by the author, the contribution at hand suggests that PSS’ foundational notion of emancipatory relevance needs to be revisited. It argues that if a research project is to sustainably benefit young co-researchers, the technical relevance of the expected mutual emancipation should as well be explicitly considered in the project design. A discussion of recent methodological developments in child-targeted Participatory Design (PD) and Human-Computer Interaction (HCI) serve as inspiration for this conceptual specification. The contribution thereby invites co-research to further investigate how emancipatory relevance cannot only to be methodologically attained via dissemination of research results and conceptual developments, but also via the actual research process it attempts to engage the co-researchers in irrespective of their age

Designing psychological co-research of emancipatory-technical relevance across age thresholds

The requirement that theoretical and empirical research is to sustainably benefit not only the nominal researcher, but also the other research participants, is deeply embedded in the conceptual-analytical framework of Psychology from the Standpoint of the Subject (PSS) and its co-researcher principle. PSS research is thus to be of emancipatory relevance to those others the researcher comes to collaborate with. Meanwhile, the question of how this requirement can be prospectively integrated into the design of a research project remains subject to debate. This question emerges as particularly difficult to tackle in research projects that engage in co-research with young children: How can a researcher ensure that the young children s-he works togethe with benefit from the research project? Based on the critical analysis of an earlier research project implemented by the author, the contribution at hand suggests that PSS’ foundational notion of emancipatory relevance needs to be revisited. It argues that if a research project is to sustainably benefit young co-researchers, the technical relevance of the expected mutual emancipation should as well be explicitly considered in the project design. A discussion of recent methodological developments in child-targeted Participatory Design (PD) and Human-Computer Interaction (HCI) serve as inspiration for this conceptual specification. The contribution thereby invites co-research to further investigate how emancipatory relevance cannot only to be methodologically attained via dissemination of research results and conceptual developments, but also via the actual research process it attempts to engage the co-researchers in irrespective of their age