694 research outputs found

    Antenna subtraction with massive fermions at NNLO: Double real initial-final configurations

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    We derive the integrated forms of specific initial-final tree-level four-parton antenna functions involving a massless initial-state parton and a massive final-state fermion as hard radiators. These antennae are needed in the subtraction terms required to evaluate the double real corrections to ttˉt\bar{t} hadronic production at the NNLO level stemming from the partonic processes qqˉttˉqqˉq\bar{q}\to t\bar{t}q'\bar{q}' and ggttˉqqˉgg\to t\bar{t}q\bar{q}.Comment: 24 pages, 1 figure, 1 Mathematica file attache

    NNLO phase space master integrals for two-to-one inclusive cross sections in dimensional regularization

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    We evaluate all phase space master integrals which are required for the total cross section of generic 2 -> 1 processes at NNLO as a series expansion in the dimensional regulator epsilon. Away from the limit of threshold production, our expansion includes one order higher than what has been available in the literature. At threshold, we provide expressions which are valid to all orders in terms of Gamma functions and hypergeometric functions. These results are a necessary ingredient for the renormalization and mass factorization of singularities in 2 -> 1 inclusive cross sections at NNNLO in QCD.Comment: 37 pages, plus 3 ancillary files containing analytic expressions in Maple forma

    New calibration procedures for airborne turbulence measurements and accuracy of the methane fluxes during the AirMeth campaigns

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    Low-level flights over tundra wetlands in Alaska and Canada have been conducted during the Airborne Measurements of Methane Emissions (AirMeth) campaigns to measure turbulent methane fluxes in the atmosphere. In this paper we describe the instrumentation and new calibration procedures for the essential pressure parameters required for turbulence sensing by aircraft that exploit suitable regular measurement flight legs without the need for dedicated calibration patterns. We estimate the accuracy of the mean wind and the turbulence measurements. We show that airborne measurements of turbulent fluxes of methane and carbon dioxide using cavity ring-down spectroscopy trace gas analysers together with established turbulence equipment achieve a relative accuracy similar to that of measurements of sensible heat flux if applied during low-level flights over natural area sources. The inertial subrange of the trace gas fluctuations cannot be resolved due to insufficient high-frequency precision of the analyser, but, since this scatter is uncorrelated with the vertical wind velocity, the covariance and thus the flux are reproduced correctly. In the covariance spectra the −7∕3 drop-off in the inertial subrange can be reproduced if sufficient data are available for averaging. For convective conditions and flight legs of several tens of kilometres we estimate the flux detection limit to be about 4mgm−2d−1 for w′CH4′, 1.4gm−2d−1 for w′CO2′ and 4.2Wm−2 for the sensible heat flux

    Two-Loop Soft Corrections and Resummation of the Thrust Distribution in the Dijet Region

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    The thrust distribution in electron-positron annihilation is a classical precision QCD observable. Using renormalization group (RG) evolution in Laplace space, we perform the resummation of logarithmically enhanced corrections in the dijet limit, T1T\to 1 to next-to-next-to-leading logarithmic (NNLL) accuracy. We independently derive the two-loop soft function for the thrust distribution and extract an analytical expression for the NNLL resummation coefficient g3g_3. To combine the resummed expressions with the fixed-order results, we derive the log(R)\log(R)-matching and RR-matching of the NNLL approximation to the fixed-order NNLO distribution.Comment: 50 pages, 12 figures, 1 table. Few minor changes. Version accepted for publication in JHE

    The fully differential hadronic production of a Higgs boson via bottom quark fusion at NNLO

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    The fully differential computation of the hadronic production cross section of a Higgs boson via bottom quarks is presented at NNLO in QCD. Several differential distributions with their corresponding scale uncertainties are presented for the 8 TeV LHC. This is the first application of the method of non-linear mappings for NNLO differential calculations at hadron colliders.Comment: 27 pages, 13 figures, 1 lego plo

    Calculations for deep inelastic scattering using fast interpolation grid techniques at NNLO in QCD and the extraction of αs from HERA data

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    The extension of interpolation-grid frameworks for perturbative QCD calculations at next-to-next-to-leading order (NNLO) is presented for deep inelastic scattering (DIS) processes. A fast and flexible evaluation of higher-order predictions for any a posteriori choice of parton distribution functions (PDFs) or value of the strong coupling constant is essential in iterative fitting procedures to extract PDFs and Standard Model parameters as well as for a detailed study of the scale dependence. The APPLfast project, described here, provides a generic interface between the parton-level Monte Carlo program NNLOjet and both the APPLgrid and fastNLO libraries for the production of interpolation grids at NNLO accuracy. Details of the interface for DIS processes are presented together with the required interpolation grids at NNLO, which are made available. They cover numerous inclusive jet measurements by the H1 and ZEUS experiments at HERA. An extraction of the strong coupling constant is performed as an application of the use of such grids and a best-fit value of αs(MZ)=0.1170(15)exp(25)th is obtained using the HERA inclusive jet cross section data

    Antenna subtraction for gluon scattering at NNLO

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    We use the antenna subtraction method to isolate the double real radiation infrared singularities present in gluonic scattering amplitudes at next-to-next-to-leading order. The antenna subtraction framework has been successfully applied to the calculation of NNLO corrections to the 3-jet cross section and related event shape distributions in electron-positron annihilation. Here we consider processes with two coloured particles in the initial state, and in particular two-jet production at hadron colliders such as the Large Hadron Collider (LHC). We construct a subtraction term that describes the single and double unresolved contributions from the six-gluon tree-level process using antenna functions with initial state partons and show numerically that the subtraction term correctly approximates the matrix elements in the various single and double unresolved configurations.Comment: 71 pages, JHEP3 class; corrected typos, equivalent but more compact version of eq. (5.12), results unchange

    Erratum to: Calculations for deep inelastic scattering using fast interpolation grid techniques at NNLO in QCD and the extraction of αs\alpha _{\mathrm {s}} from HERA data

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    The implementation of interpolation grid techniques at NNLO and their subsequent application to the extraction of the strong coupling constant α s αs presented in Ref. [1] are based on the calculation in the framework [2,3,4]. An implementation error was found in this calculation [4] that altered the predicted cross sections for the DIS process at NNLO. While technical aspects and equations remain unchanged, reported numerical values and the extracted value of α s αs are affected. Updated figures, tables, and numbers quoted in the main text that have changed are provided. Numbering of sections and figures is as in Ref. [1]
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