Monte Carlo simulations of hard QCD radiation

Monte Carlo event generators, such as Herwig++, provide a full simulation of events at collider experiments. They give a fully exclusive description of hadronic final states and are therefore crucial tools for the planning of future experiments and analysing of data from existing experiments. The key component that allows this description of high-multiplicity final states is the parton shower. There has been much recent progress improving the parton shower description of hard radiation using exact matrix elements. This thesis describes research into implementing and improving such methods within the Herwig++ event generator. In Chapter 1, the parton-shower formalism is reviewed and the structure of event generators described. Chapter 2 details the specifics of the \textsf{Herwig++} parton shower. In Chapters 3 and 4, the POWHEG next-to-leading-order matching procedure is described, and work implementing the scheme within Herwig++ is presented. The method is implemented for the processes e+e- to hadrons and Drell-Yan vector boson production and the results are compared to experimental data from LEP and the Tevatron. This work includes the first full implementation of the truncated shower. A description of the development and implementation of a modified matrix-element merging scheme is presented in Chapter 5. This scheme is based on CKKW merging but uses an extension of the POWHEG idea to improve the method using truncated showers. The method is implemented first for final-state radiation in e+e- to hadrons and then, in Chapter 6, extended to include initial-state radiation in Drell-Yan vector boson production

Becoming-Other: Foucault, Deleuze, and the Political Nature of Thought

In this paper I employ the notion of the ‘thought of the outside’ as developed by Michel Foucault, in order to defend the philosophy of Gilles Deleuze against the criticisms of ‘elitism,’ ‘aristocratism,’ and ‘political indifference’—famously leveled by Alain Badiou and Peter Hallward. First, I argue that their charges of a theophanic conception of Being, which ground the broader political claims, derive from a misunderstanding of Deleuze’s notion of univocity, as well as a failure to recognize the significance of the concept of multiplicity in Deleuze’s thinking. From here, I go on to discuss Deleuze’s articulation of the ‘dogmatic image of thought,’ which, insofar as it takes ‘recognition’ as its model, can only ever think what is already solidified and sedimented as true, in light of existing structures and institutions of power. Then, I examine Deleuze’s reading of Foucault and the notion of the ‘thought of the outside,’ showing the ‘outside’ as the unthought that lies at the heart of thinking itself, as both its condition and its impossibility. Insofar as it is essential to thinking itself, finally, I argue that the passage of thought to the outside is not an absolute flight out of this world, as Hallward claims, but rather, a return of the different that constitutes the Self for Deleuze. Thinking is an ongoing movement of deterritorialization and reterritorialization, or as Foucault says, death and life. Thinking, as Deleuze understands it, is essentially creative; it reconfigures the virtual, thereby literally changing the world. Thinking is therefore, according to Deleuze, thoroughly political

What is the Avatar? Fiction and Embodiment in Avatar-Based Singleplayer Computer Games: Revised and Commented Edition

What are the characteristic features of avatar-based singleplayer videogames, from Super Mario Bros. to Grand Theft Auto? The author examines this question with a particular focus on issues of fictionality and realism, and their relation to cinema and Virtual Reality. Through close-up analysis and philosophical discussion, the author argues that avatar-based gaming is a distinctive and dominant form of virtual self-embodiment in digital culture. This book is a revised edition of Rune Klevjer's pioneering work from 2007, featuring a new introduction by the author and afterword by Stephan Günzel, Jörg Sternagel, and Dieter Mersch

Beyond the Standard Model Phenomenology at Next-to-Leading Order at the LHC

The methods by which modern event generators incorporate matrix elements accurate to next-to-leading order in the strong coupling for inclusive observables, as well as how such amplitudes are combined with the parton shower algorithms are overviewed and a novel implementation of both to Beyond-the-Standard-Model constructions for processes with non-coloured final states is presented. This implementation is applied to Z' models inspired on E_6 grand unified theories as well as to supersymmetric scenarios involving pair production of the supersymmetric partners to the Standard Model leptons and gauge bosons/Higgs. Total cross sections are verified to be in agreement with results from pre-existing software packages and observables inclusive in jets are presented at novel NLO accuracy with local increases in cross section properly accounted for and scale variation reduced. The modest increases in cross section and reduction in theoretical uncertainty make the use of the present implementation for searches at the Large Hadron Collider highly desirable

What is the Avatar?

What are the characteristic features of avatar-based singleplayer videogames, from Super Mario Bros. to Grand Theft Auto? Rune Klevjer examines this question with a particular focus on issues of fictionality and realism, and their relation to cinema and Virtual Reality. Through close-up analysis and philosophical discussion, Klevjer argues that avatar-based gaming is a distinctive and dominant form of virtual self-embodiment in digital culture. This book is a revised edition of Rune Klevjer's pioneering work from 2007, featuring a new introduction by the author and afterword by Stephan Günzel, Jörg Sternagel, and Dieter Mersch

Multi-jet Phenomenology for Hadron Colliders in the High Energy Limit

We have incorporated next-to-leading logarithmic corrections into the High Energy Jets (HEJ) formalism and parton-level Monte Carlo generator for $W$ plus inclusive dijet production. This has involved an analytic demonstration of factorisation for the relevant configurations, an extraction of the effective current and proof of its gauge invariance. We have thoroughly validated our numerical implementation and matching of the cross section to leading order accuracy. We have studied the impact of these corrections upon transverse momentum distributions and found a significant improvement in the description of data. We also present a new merging algorithm, inspired by the CKKW-L method, for combining high energy and soft-collinear logarithms. This has been implemented for HEJ+\textsc{Pythia}. Multiple parton interactions and hadronisation effects are also accounted for, allowing for an accurate description of jets shapes. We find good agreement with data for observables such as the average number of jets and gap fractions which are relevant for understanding the impact of jet vetoes

Hadronic vacuum polarization: comparing lattice QCD and data-driven results in systematically improvable ways

The precision with which hadronic vacuum polarization (HVP) is obtained determines how accurately important observables, such as the muon anomalous magnetic moment, a_\mu, or the low-energy running of the electromagnetic coupling, \alpha, are predicted. The two most precise approaches for determining HVP are: dispersive relations combined with e+e- to hadrons cross-section data, and lattice QCD. However, the results obtained in these two approaches display significant tensions, whose origins are not understood. Here we present a framework that sheds light on this issue and, if the two approaches can be reconciled, allows them to be combined. Via this framework, we test the hypothesis that the tensions can be explained by modifying the R-ratio in different intervals of center-of-mass energy sqrt(s). As ingredients, we consider observables that have been precisely determined in both approaches. These are the leading hadronic contributions to a_\mu, to the so-called intermediate window observable and to the running of \alpha between spacelike virtualities 1GeV^2 and 10GeV^2 (for which only a preliminary lattice result exists). Our tests take into account all uncertainties and correlations, as well as uncertainties on uncertainties in the lattice results. Among our findings, the most striking is that results obtained in the two approaches can be made to agree for all three observables by modifying the \rho peak in the experimental spectrum. In particular, we find that this requires a common ~5\% increase in the contributions of the peak to each of the three observables. This finding is robust against the presence or absence of one of the constraining observables. However, such an increase is much larger than the uncertainties on the measured R-ratio. We also discuss a variety of generalizations of the methods used here, as well as the limits in the information that can be extracted...Comment: 38 pages, 8 figure