Mixed QCD-electroweak O(\alpha_s\alpha) corrections to Drell-Yan processes in the resonance region: pole approximation and non-factorizable corrections

Drell-Yan-like W-boson and Z-boson production in the resonance region allows for high-precision measurements that are crucial to carry experimental tests of the Standard Model to the extremes, such as the determination of the W-boson mass and the effective weak mixing angle. In this article, we establish a framework for the calculation of the mixed QCD-electroweak O(\alpha_s\alpha) corrections to Drell-Yan processes in the resonance region, which are one of the main remaining theoretical uncertainties. We describe how the Standard Model prediction can be successfully performed in terms of a consistent expansion about the resonance poles, which classifies the corrections in terms of factorizable and non-factorizable contributions. The former can be attributed to the W/Z production and decay subprocesses individually, while the latter link production and decay by soft-photon exchange. At next-to-leading order we compare the full electroweak corrections with the pole-expanded approximations, confirming the validity of the approximation. At O(\alpha_s\alpha), we describe the concept of the expansion and explicitly give results on the non-factorizable contributions, which turn out to be phenomenologically negligible. Our results, thus, demonstrate that for phenomenological purposes the O(\alpha_s\alpha) corrections can be factorized into terms associated with initial-state and/or final-state corrections. Moreover, we argue that the factorization properties of the non-factorizable corrections at O(\alpha_s\alpha) from lower-order O(\alpha_s) graphs generalize to any order in O(\alpha_s^n\alpha).Comment: 56 pages, 22 figure

Next-to-leading-order QCD and electroweak corrections to WWW production at proton-proton colliders

Triple-W-boson production in proton-proton collisions allows for a direct access to the triple and quartic gauge couplings and provides a window to the mechanism of electroweak symmetry breaking. It is an important process to test the Standard Model (SM) and might be background to physics beyond the SM. We present a calculation of the next-to-leading order (NLO) electroweak corrections to the production of WWW final states at proton-proton colliders with on-shell W bosons and combine the electroweak with the NLO QCD corrections. We study the impact of the corrections to the integrated cross sections and to kinematic distributions of the W bosons. The electroweak corrections are generically of the size of 5-10% for integrated cross sections and become more pronounced in specific phase-space regions. The real corrections induced by quark-photon scattering turn out to be as important as electroweak loops and photon bremsstrahlung corrections, but can be reduced by phase-space cuts. Considering that prior determinations of the photon parton distribution function (PDF) involve rather large uncertainties, we compare the results obtained with different photon PDFs and discuss the corresponding uncertainties in the NLO predictions. Moreover, we determine the scale and total PDF uncertainties at the LHC and a possible future 100 TeV pp collider.Comment: 15 pages, 9 figures, 5 tables, revised version, published in JHE

Weak radiative corrections to dijet production at hadron colliders

We present the calculation of the most important electroweak corrections to dijet production at the LHC and the Tevatron, comprising tree-level effects of O(\alpha_s\alpha,\alpha^2) and weak loop corrections of O(\alpha_s^2\alpha). Although negligible for integrated cross sections, these corrections can reach 10-20% in the TeV range for transverse jet momenta k_T. Our detailed discussion of numerical results comprises distributions in the dijet invariant mass and in the transverse momenta of the leading and subleading jets. We find that the weak loop corrections amount to about -12% and -10% for leading jets with k_T~3TeV at the 14TeV LHC and k_T~800GeV at the Tevatron, respectively. The electroweak tree-level contributions are of the same generic size and typically positive at the LHC and negative at the Tevatron at high energy scales. Generally the corrections to the dijet invariant mass distributions are smaller by at least a factor of two as compared to the corresponding reach in the k_T distributions, because unlike the k_T spectra the invariant-mass distributions are not dominated by the Sudakov regime at high energy scales.Comment: 37 pages, latex, 22 figure

Techniques for the treatment of IR divergences in decay processes at NLO and application to the top-quark decay

We present the extension of two general algorithms for the treatment of infrared singularities arising in electroweak corrections to decay processes at next-to-leading order: the dipole subtraction formalism and the one-cutoff slicing method. The former is extended to the case of decay kinematics which has not been considered in the literature so far. The latter is generalized to production and decay processes with more than two charged particles, where new "surface" terms arise. Arbitrary patterns of massive and massless external particles are considered, including the treatment of infrared singularities in dimensional or mass regularization. As an application of the two techniques we present the calculation of the next-to-leading-order QCD and electroweak corrections to the top-quark decay width including all off-shell and decay effects of intermediate W bosons. The result, e.g., represents a building block of a future calculation of NLO electroweak effects to off-shell top-quark pair (WWbb) production. Moreover, this calculation can serve as the first step towards an event generator for top-quark decays at next-to-leading order accuracy, which can be used to attach top-quark decays to complicated many-particle top-quark processes, such as for tt+H or tt+jets.Comment: 37 pages, 8 figure

NNLO predictions for dijet production in diffractive DIS

Cross sections for inclusive dijet production in diffractive deep-inelastic scattering are calculated for the first time in next-to-next-to-leading order (NNLO) accuracy. These cross sections are compared to several HERA measurements published by the H1 and ZEUS collaborations. We computed the total cross sections, 49 single-differential and five double-differential distributions for six HERA measurements. The NNLO corrections are found to be large and positive. The normalization of the resulting predictions typically exceeds the data, while the kinematical shape of the data is described better at NNLO than at next-to-leading order (NLO). Our results use the currently available NLO diffractive parton distributions, and the discrepancy in normalization highlights the need for a consistent determination of these distributions at NNLO accuracy