Subtraction method for NLO corrections in Monte-Carlo event generators for Z boson production

We use a subtraction method to construct NLO corrections in a Monte-Carlo event generator for the case of vector boson production in Drell-Yan processes. Our calculations are carried out both for the Bengtsson-Sjostrand-van Zijl (BSZ) algorithm and for a modified algorithm proposed by Collins. In the case of the modified algorithm, we compute the relation between the parton distribution functions and the ones in the MSbar scheme; this relation is the same as the corresponding relation for DIS. For the BSZ algorithm, we show that there is no simple relation.Comment: 16 pages, 4 figures, JHEP class. Misprints correcte

Renormalization-group anatomy of transverse-momentum dependent parton distribution functions in QCD

The ultraviolet and rapidity divergences of transverse-momentum dependent parton distribution functions with lightlike and transverse gauge links is studied, also incorporating a soft eikonal factor. We find that in the light-cone gauge with $q^-$-independent pole prescriptions extra divergences appear which amount, at one-loop, to a cusp-like anomalous dimension. We show that such contributions are absent when the Mandelstam-Leibbrandt prescription is used. In the first case, the soft factor cancels the anomalous-dimension defect, while in the second case its ultraviolet-divergent part reduces to unity.Comment: 10 pages, 3 figures; needs ws-mpla-hep.cls (supplied). Talk presented by the first author at Workshop on "Recent Advances in Perturbative QCD and Hadronic Physics", 20--25 July 2009, ECT*, Trento, Italy, in Honor of Prof. Anatoly Efremov's 75th birthda

Systematic Visuo-Textual Analysis: A Framework for Analysing Visual and Textual Data

As qualitative research has evolved, researchers now often combine interviews with the production of photographs, artefacts, collages, maps or drawings and the like. However, in practice, the artefacts produced are used to eliciting experiences and stimulating conversations rather than as data, per se, which is often due to the lack of guidelines for how to deal with the artefacts as data in a systematic analytical process. In this article, we present the Systematic Visuo-Textual Analysis, a framework developed to provide much-needed support for qualitative researchers in analysing artefacts in combination with interviews. Drawing on existing frameworks for visual and textual analysis the focus of this framework is to analyse visual and textual datasets separately and in conjunction with one another through several levels of interpretation from noticing descriptive elements and focussing on specific linguistic and artistic elements through to developing conceptual themes. Drawing on examples from our own research, we will demonstrate the practical application of the Systematic Visuo-Textual Analysis

Where’s the validation? Role of emotion work and validation for doctoral students

This article presents an original engagement with research into emotions in the PhD to ask ‘Where’s the validation?’ by using emotion work as a theoretical foundation. We develop a focus on emotional dissonance in the PhD journey to explore challenges around managing emotion. We explore how PhD students manage emotions around their projects and their PhD communities. Our focus in this paper is on the lived experiences of six PhD students, using reflective methods and interviews. In our analysis of the challenges PhD students face, we find that validation is a key part of the doctoral learning journey, and the emotion work that takes place. By aligning analysis of PhD emotion work with the theme of ‘validation theory’, we pinpoint how instances of validation are key to identity formation for PhD students. We argue that validation is crucial for PhD students’ wellbeing and conclude that unless identity formation as a PhD student coincides with processes of external validation, then emotional dissonance occurs

Relative distributions of W's and Z's at low transverse momenta

Despite large uncertainties in the $W^\pm$ and $Z^0$ transverse momentum ($q_T$) distributions for q_T\lsim 10 GeV, the ratio of the distributions varys little. The uncertainty in the ratio of $W$ to $Z$ $q_T$ distributions is on the order of a few percent, independent of the details of the nonperturbative parameterization.Comment: 13 pages in revtex, 5 postscript figures available upon request, UIOWA-94-0

Using LEGO® To Understand Emotion Work In Doctoral Education

In this paper, we present a project of the University of Kent Graduate School that utilises this paradox of playfulness and creativity. LEGO® is used in workshops to explore doctoral students’ emotions around the complex and solitary experience of a PhD research. We argue LEGO® is uniquely generative for exploring emotion work. After a brief overview of the background and context to the doctoral training workshop, we provide a brief review of emotion work. We then describe the LEGO® workshop we developed for our students, before explaining our approach to data collection and analysis. We then present our results, using verbatim statements from conversations with students around their LEGO® models. We present the interconnected building elements of height, walls and positioning, which are particularly impactful in highlighting the emotion work with LEGO® models. We connect the findings to a brief discussion in relation to the literature around emotion work. We have found that LEGO®’ bricks structure, solidity, and variety ensure its openness to metaphorical investment and promote the creation of narratives. Thus, building LEGO® models enabled participants to engage creatively with routinization of practices and emotion work, as well their positive support networks. We conclude with final thoughts on the value of LEGO® and steps for further developing the existing workshop

Next-to-Leading Order Hard Scattering Using Fully Unintegrated Parton Distribution Functions

We calculate the next-to-leading order fully unintegrated hard scattering coefficient for unpolarized gluon-induced deep inelastic scattering using the logical framework of parton correlation functions developed in previous work. In our approach, exact four-momentum conservation is maintained throughout the calculation. Hence, all non-perturbative functions, like parton distribution functions, depend on all components of parton four-momentum. In contrast to the usual collinear factorization approach where the hard scattering coefficient involves generalized functions (such as Dirac $\delta$-functions), the fully unintegrated hard scattering coefficient is an ordinary function. Gluon-induced deep inelastic scattering provides a simple illustration of the application of the fully unintegrated factorization formalism with a non-trivial hard scattering coefficient, applied to a phenomenologically interesting case. Furthermore, the gluon-induced process allows for a parameterization of the fully unintegrated gluon distribution function.Comment: 22 pages, Typos Fixed, Reference Added, Minor Clarification Adde

Fully Unintegrated Parton Correlation Functions and Factorization in Lowest Order Hard Scattering

Motivated by the need to correct the potentially large kinematic errors in approximations used in the standard formulation of perturbative QCD, we reformulate deeply inelastic lepton-proton scattering in terms of gauge invariant, universal parton correlation functions which depend on all components of parton four-momentum. Currently, different hard QCD processes are described by very different perturbative formalisms, each relying on its own set of kinematical approximations. In this paper we show how to set up formalism that avoids approximations on final-state momenta, and thus has a very general domain of applicability. The use of exact kinematics introduces a number of significant conceptual shifts already at leading order, and tightly constrains the formalism. We show how to define parton correlation functions that generalize the concepts of parton density, fragmentation function, and soft factor. After setting up a general subtraction formalism, we obtain a factorization theorem. To avoid complications with Ward identities the full derivation is restricted to abelian gauge theories; even so the resulting structure is highly suggestive of a similar treatment for non-abelian gauge theories.Comment: 44 pages, 69 figures typos fixed, clarifications and second appendix adde

The space-time structure of hard scattering processes

Recent studies of exclusive electroproduction of vector mesons at JLab make it possible for the first time to play with two independent hard scales: the virtuality Q^2 of the photon, which sets the observation scale, and the momentum transfer t to the hadronic system, which sets the interaction scale. They reinforce the description of hard scattering processes in terms of few effective degrees of freedom relevant to the Jlab-Hermes energy range.Comment: 4 pages; 5 figure

Making sense of cultural bumps: Supporting international graduate teaching assistants with their teaching

This article reports on a study with over 100 Graduate Teaching Assistants (GTAs), 69 of whom were international GTAs. We explore their experiences of ‘cultural bumps’ in their transition into one UK University. Following the principles of practice-based enquiry, data collection combined interviews with data generated in workshops, including transcripts, fieldnotes, student feedback and LEGO® models. We focus on three themes of starting teaching, essay marking and classroom boundaries to explore ‘cultural bumps’ where GTAs experience adjustment stresses transitioning into UK higher education teaching. We connect ‘cultural bumps’ to challenges reconciling teaching and researcher roles for GTAs. We conclude with an agenda for research work to further develop our understanding of international GTAs’ experiences