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Register a new userQCD parton showers and NLO EW corrections to Drell-Yan
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Authors
P. Richardson
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We report on the implementation of an interface between the SANC generator framework for Drell-Yan hard processes, which includes next-to-leading order electroweak (NLO EW) corrections, and the Herwig++ and Pythia8 QCD parton shower Monte Carlos. A special aspect of this implementation is that the initial-state shower evolution in both shower generators has been augmented to handle the case of an incoming photon-in-a-proton, diagrams for which appear at the NLO EW level. The difference between shower algorithms leads to residual differences in the relative corrections of 2-3% in the p_T(mu) distributions at p_T(mu)>~50 GeV (where the NLO EW correction itself is of order 10%).
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The relevance of single-W and single-Z production processes at hadron colliders is well known: in the present paper the status of theoretical calculations of Drell-Yan processes is summarized and some results on the combination of electroweak and QCD corrections to a sample of observables of the process $p p to W^pm to mu^pm + X$ at the LHC are discussed. The phenomenological analysis shows that a high-precision knowledge of QCD and a careful combination of electroweak and strong contributions is mandatory in view of the anticipated LHC experimental accuracy. One of the authors (O.N.) dedicates these notes to Prof. S. Jadach, in honour of his 60th birthday and grateful for all that Prof. Jadach taught him during their fruitful collaboration.
We present the first calculation of the full next-to-leading-order electroweak and QCD corrections for vector-boson scattering (VBS) into a pair of Z bosons at the LHC. We consider specifically the process ${rm ppto e^{+}e^{-}mu^{+}mu^{-}jj}+X$ at orders $mathcal{O}(alpha^7)$ and $mathcal{O}(alpha_salpha^6)$ and take all off-shell and interference contributions into account. Owing to the presence of enhanced Sudakov logarithms, the electroweak corrections amount to $-16%$ of the leading-order electroweak fiducial cross section and induce significant shape distortions of differential distributions. The QCD corrections on the other hand are larger ($+24%$) than typical QCD corrections in VBS. This originates from considering the full computation including tri-boson contributions in a rather inclusive phase space. We also provide a leading-order analysis of all contributions to the cross section for ${rm pp to e^{+}e^{-}mu^{+}mu^{-}jj}+X$ in a realistic setup.
We present the full next-to-next-to-leading order (NNLO) corrections to the coefficient function for the polarized cross section $d Deltasigma/d Q$ of the Drell-Yan process. We study the effect of these corrections on the process $p+pto l^+l^-+`X$ at an C.M. energy $sqrt{S}=200 GeV$. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for a lepton pair invariant mass $Q<50 GeV$. For this reaction the dominant subprocess is given by $q+bar qto gamma^*+`X$ and its higher order corrections so that it provides us with an excellent tool to measure the polarized sea-quark densities.
Drell Yan production is a sensitive probe of new physics and as such has been calculated to high order in both the electroweak and QCD sectors of the Standard Model, allowing for precision comparisons between theory and data. Here we extend these calculations to the Standard Model Effective field theory (SMEFT) and present the NLO QCD and electroweak contributions to the neutral Drell Yan process that are linear in the Wilson coefficients of the SMEFT theory.
Measuring the polarization of electroweak bosons at the LHC allows for important tests of the electroweak-symmetry-breaking mechanism that is realized in nature. Therefore, precise Standard Model predictions are needed for the production of polarized bosons in the presence of realistic kinematic selections. We formulate a method for the calculation of polarized cross-sections at NLO that relies on the pole approximation and the separation of polarized matrix elements at the amplitude level. In this framework, we compute NLO-accurate cross-sections for the production of two polarized Z bosons at the LHC, including for the first time NLO EW corrections and combining them with NLO QCD corrections and contributions from the gluon-induced process.
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