We present the total cross sections at next-to-next-to-leading order in the strong coupling for Higgs boson production via weak-boson fusion. Our results are obtained via the structure function approach, which builds upon the approximate, though very accurate, factorization of the QCD corrections between the two quark lines. The theoretical uncertainty on the total cross sections at the LHC from higher order corrections and the parton distribution uncertainties are estimated at the 2% level each for a wide range of Higgs boson masses.
Weak vector boson fusion provides a unique channel to directly probe the mechanism of electroweak symmetry breaking at hadron colliders. We present a method that allows to calculate total cross sections to next-to-next-to-leading order (NNLO) in QCD for an arbitrary V * V * → X process, the so-called structure function approach. By discussing the case of Higgs production in detail, we estimate several classes of previously neglected contributions and we argue that such method is accurate at a precision level well above the typical residual scale and PDF uncertainties at NNLO. Predictions for cross sections at the Tevatron and the LHC are presented for a variety of cases: the Standard Model Higgs (including anomalous couplings), neutral and charged scalars in extended Higgs sectors and (fermiophobic) vector resonance production. Further results can be easily obtained through the public use of the VBF@NNLO code.
Abstract:We perform the integration of all iterated singly-unresolved subtraction terms, as defined in ref. [1], over the two-particle factorized phase space. We also sum over the unresolved parton flavours. The final result can be written as a convolution (in colour space) of the Born cross section and an insertion operator. We spell out the insertion operator in terms of 24 basic integrals that are defined explicitly. We compute the coefficients of the Laurent expansion of these integrals in two different ways, with the method of Mellin-Barnes representations and sector decomposition. Finally, we present the Laurent-expansion of the full insertion operator for the specific examples of electron-positron annihilation into two and three jets.
We develop a new formalism for computing and including both the perturbative
and nonperturbative QCD contributions to the scale evolution of average gluon
and quark jet multiplicities. The new method is motivated by recent progress in
timelike small-x resummation obtained in the MS-bar factorization scheme. We
obtain next-to-next-to-leading-logarithmic (NNLL) resummed expressions, which
represent generalizations of previous analytic results. Our expressions depend
on two nonperturbative parameters with clear and simple physical
interpretations. A global fit of these two quantities to all available
experimental data sets that are compatible with regard to the jet algorithms
demonstrates by its goodness how our results solve a longstandig problem of
QCD. We show that the statistical and theoretical uncertainties both do not
exceed 5% for scales above 10 GeV. We finally propose to use the jet
multiplicity data as a new way to extract the strong-coupling constant.
Including all the available theoretical input within our approach, we obtain
alpha_s^(5)(M_Z)=0.1199 +- 0.0026 in the MS-bar scheme in an approximation
equivalent to next-to-next-to-leading order enhanced by the resummations of
ln(x) terms through the NNLL level and of ln(Q^2) terms by the renormalization
group, in excellent agreement with the present world average.Comment: 33 pages, 11 figures; two more experimental data sets included;
accepted for publication in Nucl. Phys.
We present a derivation of the threshold resummation formula for the Drell-Yan rapidity distribution. Our argument is valid for all values of rapidity and to all orders in perturbative QCD and can be applied to all Drell-Yan processes in a universal way, i.e. both for the production of a virtual photon γ * and the production of a vector boson W ± , Z 0 . We show that for the fixedtarget experiment E866/NuSea used in current parton fits, the NLL resummation corrections are comparable to NLO fixed-order corrections and are crucial to obtain agreement with the data.
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