We describe a calculation of the O(α 2 s ) QCD corrections to the fully differential cross section for W and Z boson production in hadronic collisions. The result is fully realistic in that it includes spin correlations, finite width effects, γ − Z interference and allows for the application of arbitrary cuts on the leptonic decay products of the W and Z. We have implemented this calculation into a numerical program. We demonstrate the use of this code by presenting phenomenological results for several future LHC analyses and recent Tevatron measurements, including the W cross section in the forward rapidity region and the central over forward cross section ratio.

The "anarchic" Randall-Sundrum model of flavor is a low energy solution to both the electroweak hierarchy and flavor problems. Such models have a warped, compact extra dimension with the standard model fermions and gauge bosons living in the bulk, and the Higgs living on or near the TeV brane. In this paper we consider bounds on these models set by lepton flavor violation constraints. We find that loop-induced decays of the form l → l ′ γ are ultraviolet sensitive and uncalculable when the Higgs field is localized on a four-dimensional brane; this drawback does not occur when the Higgs field propagates in the full five-dimensional space-time. We find constraints at the few TeV level throughout the natural range of parameters, arising from µ − e conversion in the presence of nuclei, rare µ decays, and rare τ decays. A "tension" exists between loopinduced dipole decays such as µ → eγ and tree-level processes such as µ − e conversion; they have opposite dependences on the five-dimensional Yukawa couplings, making it difficult to decouple flavor-violating effects. We emphasize the importance of the future experiments MEG and PRIME. These experiments will definitively test the Randall-Sundrum geometric origin of hierarchies in the lepton sector at the TeV-scale.

Centre d'études et d'expertise sur les risques, l'environnement, la mobilité et l'aménagement

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We propose a new method of computing real emission contributions to hard QCD processes. Our approach uses sector decomposition of the exclusive final-state phase space to enable extraction of all singularities of the real emission matrix elements before integration over any kinematic variable. The exact kinematics of the real emission process are preserved in all regions of phase space. Traditional approaches to extracting singularities from real emission matrix elements, such as phase space slicing and dipole subtraction, require both the determination of counterterms for double real emission amplitudes in singular kinematic limits and the integration of these contributions analytically to cancel the resulting singularities against virtual corrections. Our method addresses both of these issues. The implementation of constraints on the final-state phase space, including various jet algorithms, is simple using our approach. We illustrate our method using e + e − → jets at O(α 2 S ) as an example.

We compute the rapidity distribution of the virtual photon produced in the Drell-Yan process through next-to-next-to-leading order in perturbative QCD. We introduce a powerful new method for calculating differential distributions in hard scattering processes. This method is based upon a generalization of the optical theorem; it allows the integration-by-parts technology developed for multi-loop diagrams to be applied to non-inclusive phase-space integrals, and permits a high degree of automation. We apply our results to the analysis of fixed target experiments.PACS numbers: 12.38. Bx,13.85.Qk The production of lepton pairs in hadronic collisions, known as the Drell-Yan (DY) process [1], was the first application of parton model ideas beyond deep inelastic scattering. Due to its clean theoretical interpretation in terms of quark-antiquark annihilation into a vector boson, and large event rates, the DY process has been studied extensively, and will continue to be investigated at both the Tevatron and the LHC. The DY process provides valuable information about parton distribution functions (pdfs), enables measurements of the production rates and masses of W and Z bosons, and furnishes a sensitive test for many varieties of new physics, such as the additional gauge bosons that appear in many extensions of the Standard Model. It will also be used for the more prosaic purpose of monitoring partonic luminosities at the LHC.Despite the importance of the DY process and the significant amount of work devoted to its description, the calculation of higher order QCD corrections has proceeded slowly. The next-to-leading order (NLO) QCD corrections to the total cross section, and the x F and rapidity distributions, were calculated nearly 25 years ago [2]; the NNLO corrections to the total cross section were obtained eleven years later [3]. No complete calculation of the NNLO QCD corrections to any differential distribution has been performed, although partial results exist [4].Recently, the NNLO virtual corrections to several interesting hard scattering processes in QCD have been computed [5]; however, the calculation of real emission contributions, required for complete NNLO predictions, is still in progress. These contributions entail a careful analysis of perturbative multiparticle final states in generic hard scattering events. While it is certainly useful to solve this problem in complete generality, it is also useful to study specific examples, especially those most urgently needed in experimental analyses. It is possible to develop alternative methods of calculation which can be used to compute basic differential distributions.In Refs. [6,7] it was shown how to combine the optical theorem with multi-loop computational methods to compute phase space integrals. In this Letter we present a non-trivial application of these ideas; we compute the rapidity distribution of the virtual photon produced in the DY process through NNLO in perturbative QCD.We shall apply our results to the production of lepton pairs in proton-prot...

We present the complete calculation of W-boson production in association with a jet in hadronic collisions through next-to-next-to-leading order (NNLO) in perturbative QCD. To cancel infrared divergences, we discuss a new subtraction method that exploits the fact that the N-jettiness event-shape variable fully captures the singularity structure of QCD amplitudes with final-state partons. This method holds for processes with an arbitrary number of jets and is easily implemented into existing frameworks for higher-order calculations. We present initial phenomenological results for W+jet production at the LHC. The NNLO corrections are small and lead to a significantly reduced theoretical error, opening the door to precision measurements in the W+jet channel at the LHC.

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