571 research outputs found
Antenna subtraction with massive fermions at NNLO: Double real initial-final configurations
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
hadronic production at the NNLO level stemming from the partonic
processes and .Comment: 24 pages, 1 figure, 1 Mathematica file attache
NNLO phase space master integrals for two-to-one inclusive cross sections in dimensional regularization
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
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
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, 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 . To combine the resummed expressions with the fixed-order
results, we derive the -matching and -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
Two-loop Sudakov form factor in ABJM
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited
Erratum to: Calculations for deep inelastic scattering using fast interpolation grid techniques at NNLO in QCD and the extraction of from HERA data
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]
Differential equations and massive two-loop Bhabha scattering: the B5l2m3 case
The two-loop box contributions to massive Bhabha scattering may be reduced to
two-loop box master integrals (MIs) with five, six, and seven internal lines,
plus vertices and self energies. The self-energy and vertex MIs may be solved
analytically by the differential equations (DE) method. This is true for only
few of the box masters. Here we describe some details of the analytical
determination, including constant terms in ep=(4-d)/2, of the complicated
topology B5l2m3 (with 5 lines, 2 of them being massive). With the DE approach,
three of the four coupled masters have been solved in terms of (generalized)
standard Harmonic Polylogarithms.Comment: 5 pages, 2 figures, contribution to RADCOR 2005, Oct 2-7, 2005,
Shonan Village, Japan, to appear in Nucl. B (Proc. Suppl.
Double-Spin Asymmetry of J/psi Production in Polarized pp Collisions at HERA-
We calculated the color-octet contribution to the double spin asymmetry of
hadroproduction with nonzero transverse momenta at fixed target
energies GeV. It is shown that the color-octet contribution
is dominant in the asymmetries. The expected asymmetries and statistical errors
in a future option of HERA with longitudinally polarized protons at HERA- should allow one to distinguish between different parametrizations for the
polarized gluon distribution in the proton.Comment: 14 pages with 6 figures (epsfig), LaTeX; Some figures are changed and
misprint is correcte
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