464 research outputs found

    Double real radiation corrections to gluon scattering at NNLO

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    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

    Infrared structure of e+e3e^+e^- \to 3 jets at NNLO: QED-type contributions

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    The NNLO QCD corrections to the e+e3e^+e^- \to 3 jets can be decomposed according to their colour factors. Out of the seven colour factors, three are of QED-type: 1/N21/N^2, NF/NN_F/N and NF2N_F^2. We use the antenna subtraction method to compute these contributions, providing complete expressions for the subtraction terms in NF/NN_F/N and NF2N_F^2.Comment: Talk presented at Loops and Legs 2006, Eisenac

    Two-Loop Quark and Gluon Form Factors in Dimensional Regularisation

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    We compute the two-loop corrections to the massless quark form factor γqqˉ\gamma^* \to q\bar q and gluon form factor HggH\to gg to all orders in the dimensional regularisation parameter ϵ=(4d)/2\epsilon=(4-d)/2. The two-loop contributions to the form factors are reduced to linear combinations of master integrals, which are computed in a closed form, expressed as Γ\Gamma-functions and generalised hypergeometric functions of unit argument. Using the newly developed HypExp-package, these can be expanded to any desired order, yielding Laurent expansions in ϵ\epsilon. We provide expansions of the form factors to order ϵ2\epsilon^2, as required for ultraviolet renormalisation and infrared factorisation of the three-loop form factors.Comment: 9 pages, latex, references update

    The sector decomposition approach to real radiation at NNLO

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    A method based on sector decomposition is briefly described which is suitable for the calculation of the double real radiation part of e^+e^- to 3 jets at next-to-next-to-leading order in a fully differential way.Comment: 5 pages, 2 figures, to appear in the proceedings of the 7th International Symposium on Radiative Corrections (RADCOR05), Shonan Village, Japan, 200

    Light fermionic NNLO QCD corrections to top-antitop production in the quark-antiquark channel

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    We present the NNLO corrections to top pair production in the quark-antiquark channel proportional to the number of light quark flavors NlN_l. While the double real corrections were derived previously, here we compute the real-virtual and virtual-virtual contributions in this partonic channel. Using the antenna subtraction formalism, we show that the subtraction terms correctly approximate the real-virtual contributions in all their infrared limits. Combined with the integrated forms of the double real and real-virtual subtraction terms, we show analytically that the explicit infrared poles cancel at the real-virtual and virtual-virtual levels respectively, thereby demonstrating the validity of the massive extension of the NNLO antenna formalism. These NNLO corrections are implemented in a Monte Carlo parton level generator providing full kinematical information on an event-by event basis. With this program, NNLO differential distributions in the form of binned histograms are obtained and presented here.Comment: 42 pages, 8 figure

    NNLO Antenna Subtraction with One Hadronic Initial State

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    In this talk we present the extension of the antenna subtraction method to include initial states containing one hadron at NNLO. We sketch the requirements for the different necessary subtraction terms, and we explain how the antenna functions are integrated over the appropriate phase space by reducing the integrals to a small set of master integrals. Where applicable, our results for the integrated antennae were cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.Comment: 6 pages, 1 figure. Talk given at RADCOR 2009 - 9th International Symposium on Radiative Corrections (Applications of Quantum Field Theory to Phenomenology) October 25 - 30 200

    Isolated Photons in Deep Inelastic Scattering

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    Photon radiation at large transverse momenta at colliders is a detailed probe of hard interaction dynamics. The isolated photon production cross section in deep inelastic scattering was measured recently by the ZEUS experiment, and found to be considerably larger than theoretical predictions obtained with widely used event generators. To investigate this discrepancy, we perform a dedicated parton-level calculation of this observable, including contributions from fragmentation and large-angle radiation. Our results are in good agreement with all aspects of the experimental measurement.Comment: 4 pages, 3 figure
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