Abstract: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 (α s α, α 2 ) and weak loop corrections of O (α 2 s α). 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 ∼ 3 TeV at the 14 TeV LHC and k T ∼ 800 GeV 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 invariantmass distributions are not dominated by the Sudakov regime at high energy scales.

We present a framework for performing a comprehensive analysis of a large class of supersymmetric models, including spectrum calculation, dark matter studies and collider phenomenology. To this end, the respective model is defined in an easy and straightforward way using the \Mathematica package SARAH. SARAH then generates model files for CalcHep which can be used with MicrOmegas as well as model files for WHIZARD and OMEGA. In addition, Fortran source code for SPheno is created which facilitates the determination of the particle spectrum using two-loop renormalization group equations and one-loop corrections to the masses. As an additional feature, the generated SPheno code can write out input files suitable for use with HiggsBounds to apply bounds coming from the Higgs searches to the model. Combining all program provides a closed chain from model building to phenomenology.Comment: 68 pages, 7 figure

Abstract:We present the calculation of next-to-leading-order electroweak corrections to W-boson pair production at the LHC, taking off-shell effects of the W bosons and their leptonic decays into account in the framework of the so-called double-pole approximation. In detail, the lowest-order cross section and the photonic bremsstrahlung are based on full matrix elements with four-fermion final states, but the virtual one-loop corrections are approximated by the leading contributions of a systematic expansion about the resonance poles of the two W bosons. This expansion classifies the virtual corrections into factorizable and non-factorizable corrections, the calculation of which is described in detail. Corrections induced by photons in the initial state, i.e. photon-photon and quark-photon collision channels, are included and based on complete matrix elements as well. Our numerical results, which are presented for realistic acceptance cuts applied to the W-boson decay products, qualitatively confirm recent results obtained for on-shell W bosons and reveal electroweak corrections of the size of tens of percent in the TeV range of transverse momenta and invariant masses. In general, photon-photon and quark-photon induced contributions amount to 5−10% of the full differential result. Compared to previous predictions based on stable W bosons electroweak corrections, however, can change by several percent because of realistic cuts on the W-boson decay products and corrections to the decays.

While Monte Carlo event generators like WHIZ-ARD have become indispensable tools in studying the impact of new physics on collider observables over the last decades, the implementation of new models in such packages has remained a rather awkward and error-prone process. Recently, the FEYNRULES package was introduced which greatly simplifies this process by providing a single unified model format from which model implementations for many different Monte Carlo codes can be derived automatically. In this note, we present an interface which extends FEYNRULES to provide this functionality also for the WHIZARD package, thus making WHIZARD's strengths and performance easily available to model builders.

For many practical purposes, it is convenient to formulate unbroken nonabelian gauge theories like QCD in a color-flow basis. We present a new derivation of SU(N ) interactions in the color-flow basis by extending the gauge group to U(N ) × U(1) ′ in such a way that the two U(1) factors cancel each other. We use the quantum action principles to show the equivalence to the usual basis to all orders in perturbation theory. We extend the known Feynman rules to exotic color representations (e.g. sextets) and discuss practical applications as they occur in automatic computation programs.