(Re)fashioning Biafra: identity, authorship and the politics of dress in half of a yellow sun and other narratives of the Nigeria-Biafra war

Chimamanda Ngozi Adichie’s second novel, Half of a Yellow (2006), is one in a long line of works by Nigerian authors to portray the Nigeria-Biafra War (1967-1970). While Adichie has stated that she wanted to make modern Nigeria aware of its history by writing the novel, the writer has also revealed that she drew from past literary portrayals to construct her narrative. In order to untangle the complex construction of Half of a Yellow Sun, this article explores the way the novel negotiates the literary legacy of Biafra through material fashion, which I argue elucidates this complex intertextuality. Furthermore, I contend that the novel draws attention to and critiques the way that understanding of Biafra has been dominated by novels written by male authors, and weaves threads of material fashion in order to offer a new way of negotiating Nigerian history

Using gamma+jets Production to Calibrate the Standard Model Z(nunu)+jets Background to New Physics Processes at the LHC

The irreducible background from Z(nunu)+jets, to beyond the Standard Model searches at the LHC, can be calibrated using gamma+jets data. The method utilises the fact that at high vector boson pT, the event kinematics are the same for the two processes and the cross sections differ mainly due to the boson-quark couplings. The method relies on a precise prediction from theory of the Z/gamma cross section ratio at high pT, which should be insensitive to effects from full event simulation. We study the Z/gamma ratio for final states involving 1, 2 and 3 hadronic jets, using both the leading-order parton shower Monte Carlo program Pythia8 and a leading-order matrix element program Gambos. This enables us both to understand the underlying parton dynamics in both processes, and to quantify the theoretical systematic uncertainties in the ratio predictions. Using a typical set of experimental cuts, we estimate the net theoretical uncertainty in the ratio to be of order 7%, when obtained from a Monte Carlo program using multiparton matrix-elements for the hard process. Uncertainties associated with full event simulation are found to be small. The results indicate that an overall accuracy of the method, excluding statistical errors, of order 10% should be possible.Comment: 22 pages, 14 figures; Accepted for publication by JHE

NLO QCD corrections to WZ+jet production with leptonic decays

We compute the next-to-leading order QCD corrections to WZ+jet production at the Tevatron and the LHC, including decays of the electroweak bosons to light leptons with all off-shell effects taken into account. The corrections are sizable and have significant impact on the differential distributions.Comment: 14 pages, 7 figure

Efficiency improvements for the numerical computation of NLO corrections

In this paper we discuss techniques, which lead to a significant improvement of the efficiency of the Monte Carlo integration, when one-loop QCD amplitudes are calculated numerically with the help of the subtraction method and contour deformation. The techniques discussed are: holomorphic and non-holomorphic division into sub-channels, optimisation of the integration contour, improvement of the ultraviolet subtraction terms, importance sampling and antithetic variates in loop momentum space, recurrence relations.Comment: 34 pages, version to be publishe

Scaling Patterns for QCD Jets

Jet emission at hadron colliders follows simple scaling patterns. Based on perturbative QCD we derive Poisson and staircase scaling for final state as well as initial state radiation. Parton density effects enhance staircase scaling at low multiplicities. We propose experimental tests of our theoretical findings in Z+jets and QCD gap jets production based on minor additions to current LHC analyses.Comment: 36 pages, 16 figure

Single Cut Integration

We present an analytic technique for evaluating single cuts for one-loop integrands, where exactly one propagator is taken to be on shell. Our method extends the double-cut integration formalism of one-loop amplitudes to the single-cut case. We argue that single cuts give meaningful information about amplitudes when taken at the integrand level. We discuss applications to the computation of tadpole coefficients.Comment: v2: corrected typo in abstrac

Supersymmetric Higgs Yukawa Couplings to Bottom Quarks at next-to-next-to-leading Order

The effective bottom Yukawa couplings are analyzed for the minimal supersymmetric extension of the Standard Model at two-loop accuracy within SUSY-QCD. They include the resummation of the dominant corrections for large values of tg(beta). In particular the two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-induced SUSY-electroweak contributions are addressed. The residual theoretical uncertainties range at the per-cent level.Comment: 25 pages, 9 figures, added comments and references, typos corrected, results unchanged, published versio

NLO QCD corrections to off-shell top-antitop production with leptonic decays at hadron colliders

We present details of a calculation of the cross section for hadronic top-antitop production in next-to-leading order (NLO) QCD, including the decays of the top and antitop into bottom quarks and leptons. This calculation is based on matrix elements for \nu e e+ \mu- \bar{\nu}_{\mu}b\bar{b} production and includes all non-resonant diagrams, interferences, and off-shell effects of the top quarks. Such contributions are formally suppressed by the top-quark width and turn out to be small in the inclusive cross section. However, they can be strongly enhanced in exclusive observables that play an important role in Higgs and new-physics searches. Also non-resonant and off-shell effects due to the finite W-boson width are investigated in detail, but their impact is much smaller than naively expected. We also introduce a matching approach to improve NLO calculations involving intermediate unstable particles. Using a fixed QCD scale leads to perturbative instabilities in the high-energy tails of distributions, but an appropriate dynamical scale stabilises NLO predictions. Numerical results for the total cross section, several distributions, and asymmetries are presented for Tevatron and the LHC at 7 TeV, 8 TeV, and 14 TeV.Comment: 61 pp. Matches version published in JHEP; one more reference adde

A next-to-next-to-leading order calculation of soft-virtual cross sections

We compute the next-to-next-to-leading order (NNLO) soft and virtual QCD corrections for the partonic cross section of colourless-final state processes in hadronic collisions. The results are valid to all orders in the dimensional regularization parameter \ep. The dependence of the results on a particular process is given through finite contributions to the one and two-loop amplitudes. To evaluate the accuracy of the soft-virtual approximation we compare it with the full NNLO result for Drell-Yan and Higgs boson production via gluon fusion. We also provide a universal expression for the hard coefficient needed to perform threshold resummation up to next-to-next-to-leading logarithmic (NNLL) accuracy.Comment: 25 pages, 4 figure

Diffuse Gamma Rays: Galactic and Extragalactic Diffuse Emission

"Diffuse" gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived "average" spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.Comment: 32 pages, 28 figures, kapproc.cls. Chapter to the book "Cosmic Gamma-Ray Sources," to be published by Kluwer ASSL Series, Edited by K. S. Cheng and G. E. Romero. More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm