QCD Calculations by Numerical Integration

Calculations of observables in Quantum Chromodynamics are typically performed using a method that combines numerical integrations over the momenta of final state particles with analytical integrations over the momenta of virtual particles. I discuss a method for performing all of the integrations numerically.Comment: 9 pages including 2 figures. RevTe

Diffraction in DIS and Elsewhere

I review some of the results presented in the working group on diffraction at DIS97, with a particular emphasis on the theory of diffractive hard scattering.Comment: Talk at DIS97 Conference, Chicago, April 1997. Eleven pages including nine figure

Choosing integration points for QCD calculations by numerical integration

I discuss how to sample the space of parton momenta in order to best perform the numerical integrations that lead to a calculation of three jet cross sections and similar observables in electron-positron annihilation.Comment: 25 pages with 8 figure

An interactive approach to learning economics: The WinEcon package

Under the TLTP initiative, the Economics Consortium is developing an interactive computer‐based learning package called WinEcon. The package is directed at first‐year economics undergraduates, particularly those taking economics as a supplementary course. Using recent technological developments, the aim is both to facilitate a further increase in student numbers without a proportionate increase in teaching staff, and to provide a better method of student learning. Some key elements of WinEcon are set out in this paper and demonstrated by screens produced at Leicester University. Methods of presenting textual information that give the user control over accessing it are described. For learning difficult concepts, a visual active learning approach is discussed. It involves user interaction and step‐by‐step analysis. The importance of flexibility and choice is emphasized, and the capacity of the computer to assist in deepening and consolidating learning is shown

QCD and Monte Carlo event generators

Shower Monte Carlo event generators have played an important role in particle physics. Modern experiments would hardly be possible without them. In this talk I discuss how QCD physics is incorporated into the mathematical structure of these programs and I outline recent developments including matching between events with different numbers of hard jets and the inclusion of next-to-leading order effects.Comment: Plenary talk by D. Soper at XIV Workshop on Deep Inelastic Scattering (DIS2006

On the transverse momentum in Z-boson production in a virtuality ordered parton shower

Cross sections for physical processes that involve very different momentum scales in the same process will involve large logarithms of the ratio of the momentum scales when calculated in perturbation theory. One goal of calculations using parton showers is to sum these large logarithms. We ask whether this goal is achieved for the transverse momentum distribution of a Z-boson produced in hadron-hadron collisions when the shower is organized with higher virtuality parton splittings coming first, followed successively by lower virtuality parton splittings. We find that the virtuality ordered shower works well in reproducing the known QCD result.Comment: 60 pages with three figure

Structure of parton showers including quantum interference

It is useful to describe a leading order parton shower as the solution of a linear equation that specifies how the state of the partons evolves. This description involves an essential approximation of a strong ordering of virtualities as the shower progresses from a hard interaction to softer interactions. If this is to be the only approximation, then the partons should carry color and spin and quantum interference graphs should be included. We explain how the evolution equation for this kind of a shower can be formulated. We discuss briefly our efforts to implement this evolution equation numerically.Comment: Talk at 2008 Rencontre de Moriond, QCD session. Four page

Effects of subleading color in a parton shower

Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color (LC) approximation, which is the leading term in an expansion in powers of 1/N_\Lc^2, where N_\Lc = 3 is the number of colors. In the parton shower event generator \textsc{Deductor}, we have introduced a more general approximation, the LC+ approximation, that includes some of the color suppressed contributions. In this paper, we explore the differences in results between the LC approximation and the LC+ approximation. Numerical comparisons suggest that, for simple observables, the LC approximation is quite accurate. We also find evidence that for gap-between-jets cross sections neither the LC approximation nor the LC+ approximation is adequate.Comment: 23 pages, 13 figures, published versio