We compute the massive gauge and scalar corrections to form factors in both the Sudakov and threshold regimes up to and including two-loop orders. The corrections are calculated for processes involving two external fermions and scalars in the spontaneously broken SU(N)-Higgs model, examining a range of composite operators. Our results are general, so we discuss how our form factors are mappable from our model to the Standard Model and beyond. The effective theory formalism deployed in our work extends previous studies based on infrared evolution equations, which either neglect scalar contributions or are restricted to the Sudakov regime.
We study electroweak Sudakov effects in single W, Z and gamma production at large transverse momentum using Soft Collinear Effective Theory. We present a factorized form of the cross section near the partonic threshold with both QCD and electroweak effects included and compute the electroweak corrections arising at different scales. We analyze their size relative to the QCD corrections as well as the impact of strong-electroweak mixing terms. Numerical results for the vector-boson cross sections at the Large Hadron Collider are presented.
Resonance-aware electroweak Sudakov reweighting for multijet-merged predictions
Jožef Stefan Institute（约瑟夫·斯特凡研究所）；University of Ljubljana（卢布尔雅那大学）；Lund University（隆德大学）；INFN（意大利国家核物理研究所）；Uppsala University（乌普萨拉大学）；ELTE Eötvös Loránd University（厄特沃什·罗兰大学）；Università degli Studi di Milano（米兰大学）
Electroweak radiative corrections give rise to large negative, double-logarithmically enhanced corrections in the TeV region. These are partly compensated by real radiation and, moreover, affected by selecting isospin-noninvariant external states. We investigate the impact of real gauge boson radiation more quantitatively by considering different restricted final state configurations. We consider successively a massive abelian gauge theory, a spontaneously broken SU(2) theory and the electroweak Standard Model. We find that details of the choice of the phase space cuts, in particular whether a…
As experimental particle physics becomes more and more precise, it is becoming increasingly important for Monte Carlo simulations to improve the precision of their predictions. In terms of the hard matrix element, this means calculating to a higher order in perturbation theory. To be consistent this requires both NNLO QCD corrections and NLO EW corrections to be included. There are also interference effects between these processes that are not simple to handle consistently. For a broad description of the behaviour of NLO EW corrections at high energies, the Sudakov logarithmic approach provide…
We present an automated implementation for the calculation of one-loop double and single Sudakov logarithms stemming from electroweak radiative corrections within the Sherpa event generation framework, based on the derivation in[1]. At high energies, these logarithms constitute the leading contributions to the full NLO electroweak corrections. As examples, we show applications for relevant processes at both the LHC and future hadron colliders, namely on-shell W boson pair production, EW-induced dijet production and electron-positron production in association with four jets, providing the first…
In this addendum to Phys. Rev. D 88, no. 1, 013009 (2013), we give results for the electroweak Sudakov corrections in gauge-boson production at large transverse momentum p_T at proton colliders. In order for the results to be easily usable, we provide a simple and accurate parameterization of the corrections as a function of p_T and the center-of-mass energy \sqrt{s}. Additionally, we also discuss the dependence of the electroweak corrections on the rapidity of the produced boson, and comment on the complications that arise in the photon-production case due to isolation requirements
The Standard Model (SM) prediction of the top quark forward backward asymmetry is shown to be slightly enhanced by a correction factor of 1.05 due to electroweak Sudakov (EWS) logarithms of the form (α/sin^2 θ_W)^n log^{m< 2n} (s/M_{W,Z}^2). The EWS effect on the dijet and t \bar{t} invariant mass spectra is significant, reducing the SM prediction by ~20, 10 % respectively for the highest invariant masses measured at the LHC, and changing the shape of the high-mass tail of the spectrum. These corrections significantly affect measurements of the top quark invariant mass spectrum and the search …
Resummation of double logarithms in electroweak high energy processes
在未来TeV范围内的线性$e^+e^-$对撞机实验中，源于大质量玻色子交换的Sudakov双粒子可以导致对可观察过程的截面的显著修正。这些效应对于Next Linear Collider的高精度目标非常重要。我们利用基于规范不变色散方法的红外演化方程，得到了散射振幅的双对数渐近性，并讨论了在规范对称性破缺的情况下，如何将其应用于电弱过程的标准模型。讨论了双对数效应对无辐射过程和伴随软规范玻色子辐射过程的影响。在所有的情况下，Sudakov双矩阵被发现指数。我们还讨论了Regge类过程中出现的非Sudakov型双对数效应。
We compute the one-loop electroweak Sudakov corrections to the production process Z (nu bar{nu}) + n jets, with n = 1,2,3, in p p collisions at the LHC. It represents the main irreducible background to new physics searches at the energy frontier. The results are obtained at the leading and next-to-leading logarithmic accuracy by implementing the general algorithm of Denner-Pozzorini in the event generator for multiparton processes ALPGEN. For the standard selection cuts used by ATLAS and CMS collaborations, we show that the Sudakov corrections to the relevant observables can grow up to - 40% a…
We present a short comment on resummation of double-logarithmic (DL) contributions to decays of W and Z -bosons into charged fermion pairs. We show that resummation of DL corrections to the Z -boson decay leads to standard Sudakov form factor with the negative exponent independently of the boson is on-shell or off-shell. In contrast, the Sudakov exponent for the W - decay is negative (positive) when the W-boson is on-shell (off-shell). In this connection we consider applicability of the Dispersion Relations to the case when the imaginary parts contain infrared-divergent contributions.
We study electroweak Sudakov corrections in high energy scattering, and the cancellation between real and virtual Sudakov corrections. Numerical results are given for the case of heavy quark production by gluon collisions involving the rates $gg \to t \bar t, b \bar b, t \bar b W, t \bar t Z, b \bar b Z, t \bar t H, b \bar b H$. Gauge boson virtual corrections are related to real transverse gauge boson emission, and Higgs virtual corrections to Higgs and longitudinal gauge boson emission. At the LHC, electroweak corrections become important in the TeV regime. At the proposed 100 TeV collider, …
In this work we revisit the algorithm of Denner and Pozzorini for the calculation of one-loop electroweak Sudakov logarithms and we automate it in the MadGraph5_aMC@NLO framework. We adapt the formulas for modern calculations, keeping light-quarks and photons strictly massless and dealing with infrared divergences via dimensional regularisation. We improve the approximation by taking into account additional logarithms that are angular dependent. We prove that an imaginary term has been previously omitted and we show that it cannot be in general neglected for $2\rightarrow n$ processes with $n>…
Using the known resummation of virtual corrections together with knowledge of the leading-log structure of real radiation in a parton shower, we derive analytic expressions for the resummed real radiation after they have been integrated over all of phase space. Performing a numerical analysis for both the 13 TeV LHC and a 100 TeV $pp$ collider, we show that resummation of the real corrections is at least as important as resummation of the virtual corrections, and that this resummation has a sizable effect for partonic center of mass energies exceeding $\sqrt{s} = {\cal O}$(few TeV). For parton…
Electroweak (EW) corrections at the LHC can be enhanced at high energies due to soft/collinear radiation of W and Z bosons, being dominated by Sudakov-like corrections in the form of $α_W^l\log^n(Q^2/M_W^2)$ $(n \le 2l, α_W = α/(4π\sinθ_W^2))$ when the energy scale $Q$ enters the TeV regime. Thus, the inclusion of EW corrections in LHC predictions is important for the search of possible signals of new physics in tails of kinematic distributions. EW corrections should also be taken into account in virtue of their comparable size ($\mathcal{O}(α)$) to that of higher order QCD corrections ($\math…
We extend an effective theory framework developped in Refs. [1,2] to sum electroweak Sudakov logarithms in high energy processes to also include massive gauge bosons in the final state. The calculations require an additional regulator on top of dimensional regularization to tame the collinear singularities. We propose to use the Delta regulator, which respects soft-collinear factorization.
We consider the higher-order resummation of Sudakov double logarithms in the presence of multiple coupled gauge interactions. The associated evolution equations depend on the coupled $β$ functions of two (or more) coupling constants $α_a$ and $α_b$, as well as anomalous dimensions that have joint perturbative series in $α_a$ and $α_b$. We discuss possible strategies for solving the system of evolution equations that arises. As an example, we obtain the complete three-loop (NNLL) QCD$\otimes$QED Sudakov evolution factor. Our results also readily apply to the joint higher-order resummation of el…
Electroweak corrections to longitudinal gauge and Higgs boson scattering amplitudes are calculated. Due to Sudakov double logarithms, the effect is a suppression of amplitude that grows rapidly with increasing center of mass energy leading to significant reduction of cross sections compared to tree level results. For example, the suppression factor for the cross section of $W^+_{\text{L}}W^-_{\text{L}}$ scattering due to these corrections varies from 0.3 at the center of mass energy of $100\text{TeV}$ to a factor of $10^{-12}$ at the center of mass energy of $10^{13}\text{TeV}$. The modificati…
We present the next-to-leading order (NLO) electroweak (EW) corrections to the top quark pair production associated with a hard photon at the current and future hadron colliders. The dependence of the leading order (LO) and NLO EW corrected cross sections on the photon transverse momentum cut are investigated. We also provide the LO and NLO EW corrected distributions of the transverse momentum of final top quark and photon and the invariant mass of top quark pair and top-antitop-photon system. The results show that the NLO EW corrections are significant in high energy regions due to the EW Sud…
We consider the effect of next-to-leading order (NLO) electroweak corrections to Standard Model 2-to-2 processes, taking into account the potentially large double logarithms originating from both real and virtual corrections. A study of the leading Sudakov logarithms is presented and Bloch-Nordsieck (BN) violations are discussed for processes at the CERN Large Hadron Collider. In particular, we focus on the processes Z/photon+jet and also the ratio of Z to photon production. This ratio is known to be insensitive to NLO QCD corrections but this is not expected to be the case for the electroweak…
While radiative corrections of infrared origin normally depress high energy amplitudes (Sudakov form factors), we find that in some cases resummation of leading effects produces exponentials with positive exponents, giving rise to amplitudes that grow indefinitely with energy. The effect happens in broken gauge theories like the electroweak sector of the Standard Model, and is related to the existence of amplitudes that do not respect the gauge symmetry, and that contrary to expectations do not vanish in the very high energy limit, but rather become dominant. As a working example we consider a…
