Double real radiation corrections to gluon scattering at NNLO

We use the antenna subtraction method to isolate the double real radiation infrared singularities present in the six-gluon tree-level process at next-to-next-to-leading order. We show numerically that the subtraction term correctly approximates the matrix elements in the various single and double unresolved configurations.Comment: six pages, talk given at 10th DESY Workshop on Elementary Particle Theory, Worlitz, 25-30 April 201

Measuring the Photon Fragmentation Function at HERA

The production of final state photons in deep inelastic scattering originates from photon radiation off leptons or quarks involved in the scattering process. Photon radiation off quarks involves a contribution from the quark-to-photon fragmentation function, corresponding to the non-perturbative transition of a hadronic jet into a single, highly energetic photon accompanied by some limited hadronic activity. Up to now, this fragmentation function was measured only in electron-positron annihilation at LEP. We demonstrate by a dedicated parton-level calculation that a competitive measurement of the quark-to-photon fragmentation function can be obtained in deep inelastic scattering at HERA. Such a measurement can be obtained by studying the photon energy spectra in $\gamma + (0+1)$-jet events, where $\gamma$ denotes a hadronic jet containing a highly energetic photon (the photon jet). Isolated photons are then defined from the photon jet by imposing a minimal photon energy fraction. For this so-called democratic clustering approach, we study the cross sections for isolated $\gamma + (0+1)$-jet and $\gamma + (1+1)$-jet production as well as for the inclusive isolated photon production in deep inelastic scattering.Comment: 23 pages, LaTe

Infrared structure of e+e−→3e^+e^- \to 3 jets at NNLO: QED-type contributions

The NNLO QCD corrections to the $e^+e^- \to 3$ jets can be decomposed according to their colour factors. Out of the seven colour factors, three are of QED-type: $1/N^2$, $N_F/N$ and $N_F^2$. We use the antenna subtraction method to compute these contributions, providing complete expressions for the subtraction terms in $N_F/N$ and $N_F^2$.Comment: Talk presented at Loops and Legs 2006, Eisenac

Mechanistic artefact explanation

One thing about technical artefacts that needs to be explained is how their physical make-up, or structure, enables them to fulfil the behaviour associated with their function, or, more colloquially, how they work. In this paper I develop an account of such explanations based on the familiar notion of mechanistic explanation. To accomplish this, I outline two explanatory strategies that provide two different types of insight into an artefact’s functioning, and show how human action inevitably plays a role in artefact explanation. I then use my own account to criticize other recent work on mechanistic explanation and conclude with some general implications for the philosophy of explanation.Keywords: Artefact; Technical function; Explanation; Levels of explanation; Mechanisms

Religious exclusivism unlimited: JEROEN DE RIDDER

Like David Silver before them, Erik Baldwin and Michael Thune argue that the facts of religious pluralism present an insurmountable challenge to the rationality of basic exclusive religious belief as construed by Reformed Epistemology. I will show that their argument is unsuccessful. First, their claim that the facts of religious pluralism make it necessary for the religious exclusivist to support her exclusive beliefs with significant reasons is one that the reformed epistemologist has the resources to reject. Secondly, they fail to demonstrate that it is impossible for basic religious beliefs to return to their properly basic state after defeaters against them have been defeated. Finally, I consider whether there is perhaps a similar but better argument in the neighbourhood and conclude in the negative. Reformed Epistemology's defence of exclusivism thus remains undefeated

Towards e+e- --> 3 jets at NNLO by sector decomposition

A method based on sector decomposition has been developed to calculate the double real radiation part of the process e+e- to 3 jets at next-to-next-to-leading order. It is shown in an example that the numerical cancellation of soft and collinear poles works well. The method is flexible to include an arbitrary measurement function in the final Monte Carlo program, such that it allows to obtain differential distributions for different kinds of observables. This is demonstrated by showing 3-, 4- and 5-jet rates at order alpha_s^3 for a subpart of the process.Comment: 14 pages, 4 figure