scholarly journals A Study of QCD Radiation in VBF Higgs Production with Vincia and Pythia

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Stefan Höche ◽  
Stephen Mrenna ◽  
Shay Payne ◽  
Christian Tobias Preuss ◽  
Peter Skands
Keyword(s):  
Transverse Momentum ◽  
Radiation Pattern ◽  
Parton Shower ◽  
Vector Boson ◽  
Coherent Radiation ◽  
Higher Order ◽  
Higgs Production ◽  
Tree Level ◽  
Matrix Elements ◽  
Leading Order

We discuss and illustrate the properties of several parton-shower algorithms available in Pythia and Vincia, in the context of Higgs production via vector boson fusion (VBF). In particular, the distinctive colour topology of VBF processes allows to define observables sensitive to the coherent radiation pattern of additional jets. We study a set of such observables, using the Vincia sector-antenna shower as our main reference, and contrast it to Pythia's transverse-momentum-ordered DGLAP shower as well as Pythia's dipole-improved shower. We then investigate the robustness of these predictions as successive levels of higher-order perturbative matrix elements are incorporated, including next-to-leading-order matched and tree-level merged calculations, using Powheg Box and Sherpa respectively to generate the hard events.

scholarly journals Power corrections in a transverse-momentum cut for vector-boson production at NNLO: the qg-initiated real-virtual contribution

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Carlo Oleari ◽  
Marco Rocco
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Cross Sections ◽  
Vector Boson ◽  
Analytic Form ◽  
Leading Order ◽  
Coupling Constant ◽  
Subtraction Method ◽  
Power Corrections ◽  
Interference Contribution

AbstractWe consider the production of a vector boson (Z, $$W^\pm $$ W ± or $$\gamma ^*$$ γ ∗ ) at next-to-next-to-leading order in the strong coupling constant $$\alpha _\mathrm{S}$$ α S . We impose a transverse-momentum cutoff, $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut , on the vector boson produced in the qg-initiated channel. We then compute the power corrections in the cutoff, up to the second power, of the real-virtual interference contribution to the cumulative cross section at order $$\alpha _\mathrm{S}^2$$ α S 2 . Other terms with the same kinematics, originating from the subtraction method applied to the double-real contribution, have been also considered. The knowledge of such power corrections is a required ingredient in order to reduce the dependence on the transverse-momentum cutoff of the QCD cross sections at next-to-next-to-leading order, when the $$q_{\mathrm{T}}$$ q T -subtraction method is applied. In addition, the study of the dependence of the cross section on $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut allows as well for an understanding of its behaviour in the small transverse-momentum limit, giving hints on the structure at all orders in $$\alpha _\mathrm{S}$$ α S and on the identification of universal patterns. Our result are presented in an analytic form, using the process-independent procedure described in a previous paper for the calculation of the all-order power corrections in $$q_{\mathrm{T}}^{\mathrm{cut}}$$ q T cut .

scholarly journals On the impact of non-factorisable corrections in VBF single and double Higgs production

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Frédéric A. Dreyer ◽  
Alexander Karlberg ◽  
Lorenzo Tancredi
Keyword(s):  
Vector Boson ◽  
Relative Size ◽  
Eikonal Approximation ◽  
Higgs Production ◽  
Leading Order ◽  
Scale Uncertainty ◽  
Before And After ◽  
Depth Study ◽  
Uncertainty Band ◽  
The Impact

Abstract We study the non-factorisable QCD corrections, computed in the eikonal approximation, to Vector-Boson Fusion single and double Higgs production and show the combined factorisable and non-factorisable corrections for both processes at $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 . We investigate the validity of the eikonal approximation with and without selection cuts, and carry out an in-depth study of the relative size of the non-factorisable next-to-next-to-leading order corrections compared to the factorisable ones. In the case of single Higgs production, after selection cuts are applied, the non-factorisable corrections are found to be mostly contained within the factorisable scale uncertainty bands. When no cuts are applied, instead, the non-factorisable corrections are slightly outside the scale uncertainty band. Interestingly, for double Higgs production, we find that both before and after applying cuts, non-factorisable corrections are enhanced compared to the single Higgs case. We trace this enhancement to the existence of delicate cancellations between the various leading-order Feynman diagrams, which are partly spoiled by radiative corrections. All contributions studied here have been implemented in proVBFH v1.2.0 and proVBFHH v1.1.0.

scholarly journals SIMULATION OF Z BOSON pT SPECTRUM AT TEVATRON BY LEADING-ORDER EVENT GENERATORS

2010 ◽  
Vol 25 (36) ◽  
pp. 3047-3059 ◽  
Author(s):  
SHIGERU ODAKA
Keyword(s):  
Transverse Momentum ◽  
Z Boson ◽  
Parton Shower ◽  
Event Generator ◽  
Boson Production ◽  
Proper Solution ◽  
Leading Order

We show that the transverse momentum (pT) spectrum of Z boson production measured at Fermilab Tevatron can be well reproduced by leading-order event generators if Z + 1 jet processes are included with a proper solution for the double-count problem and if the parton shower (PS) branch kinematics are defined appropriately. The choice of the PS evolution variable does not definitely determine the low-pT behavior. Our new event generator employing the limited leading-log (LLL) subtraction and a built-in leading-log PS reproduces the spectrum very well, not only in large pT regions but also at low pT down to pT = 0.

scholarly journals Erratum: Fully Differential Vector-Boson-Fusion Higgs Production at Next-to-Next-to-Leading Order [Phys. Rev. Lett. 115 , 082002 (2015)]

2018 ◽  
Vol 120 (13) ◽  
Author(s):  
Matteo Cacciari ◽  
Frédéric A. Dreyer ◽  
Alexander Karlberg ◽  
Gavin P. Salam ◽  
Giulia Zanderighi
Keyword(s):  
Vector Boson ◽  
Higgs Production ◽  
Vector Boson Fusion ◽  
Leading Order ◽  
Fully Differential

scholarly journals Fixed-order and merged parton-shower predictions for WW and WWj production at the LHC including NLO QCD and EW corrections

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Stephan Bräuer ◽  
Ansgar Denner ◽  
Mathieu Pellen ◽  
Marek Schönherr ◽  
Steffen Schumann
Keyword(s):  
Cross Sections ◽  
Parton Shower ◽  
Higher Order ◽  
Order Effects ◽  
Leading Order ◽  
Combined Analysis ◽  
Fixed Order ◽  
Higher Order Effects ◽  
Inclusive Sample ◽  
Electroweak Corrections

Abstract First, we present a combined analysis of pp $$ \to {\mu}^{+}{v}_{\mu }{\mathrm{e}}^{-}{\overline{v}}_{\mathrm{e}} $$ → μ + v μ e − v ¯ e and pp $$ \to {\mu}^{+}{v}_{\mu }{\mathrm{e}}^{-}{\overline{v}}_{\mathrm{e}}\mathrm{j} $$ → μ + v μ e − v ¯ e j at next-to-leading order, including both QCD and electroweak corrections. Second, we provide all-order predictions for pp $$ \to {\mu}^{+}{v}_{\mu }{\mathrm{e}}^{-}{\overline{v}}_{\mathrm{e}}+ $$ → μ + v μ e − v ¯ e + jets using merged parton-shower simulations that also include approximate EW effects. A fully inclusive sample for WW production is compared to the fixed-order computations for exclusive zero- and one-jet selections. The various higher-order effects are studied in detail at the level of cross sections and differential distributions for realistic experimental set-ups. Our study confirms that merged predictions are significantly more stable than the fixed-order ones in particular regarding ratios between the two processes.

scholarly journals Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
M. I. Abdulhamid ◽  
M. A. Al-Mashad ◽  
A. Bermudez Martinez ◽  
G. Bonomelli ◽  
I. Bubanja ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Shower ◽  
Good Description ◽  
Leading Order ◽  
High Transverse Momentum ◽  
Azimuthal Correlation ◽  
Azimuthal Correlations ◽  
The Matrix ◽  
Good Agreement

AbstractThe azimuthal correlation, $$\Delta \phi _{12}$$ Δ ϕ 12 , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ s = 13  TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ Δ ϕ 12 is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi $$ Δ ϕ 12 → π , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ α s , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ Δ ϕ 12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution.

scholarly journals Precise predictions for double-Higgs production via vector-boson fusion

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Frédéric A. Dreyer ◽  
Alexander Karlberg ◽  
Jean-Nicolas Lang ◽  
Mathieu Pellen
Keyword(s):  
Cross Sections ◽  
Vector Boson ◽  
Percent Level ◽  
Higgs Production ◽  
Vector Boson Fusion ◽  
Leading Order ◽  
Fiducial Volume ◽  
Theoretical Predictions ◽  
Set Up ◽  
First Time

AbstractTheoretical predictions with next-to-next-to-leading order (NNLO) QCD accuracy combined with the next-to-leading order (NLO) electroweak (EW) corrections are presented for differential observables of the double-Higgs production process via vector-boson fusion. While the QCD corrections were previously known, the EW ones are computed here for the first time. The numerical results are obtained for a realistic experimental set-up at the LHC and are presented in the form of fiducial cross sections and differential distributions. Within this setup we find that the VBF approximation employed in the NNLO QCD correction is accurate at the sub-percent level. We find that the NLO EW corrections within the fiducial volume are $$-\,6.1\%$$ - 6.1 % , making them of almost the same order as the NLO QCD corrections. In some kinematic regions they can grow as large as $$-\,30\%$$ - 30 % making them the dominant radiative corrections. When the EW corrections are combined with the NNLO QCD corrections we find a total correction of $$-\,14.8\%$$ - 14.8 % . The results presented here thus comprise the state-of-the-art theoretical predicition for the double-Higgs production via vector-boson fusion, which will be of value to the high-luminosity programme at the LHC.

scholarly journals On improving NLO merging for $$ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $$ production

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Rikkert Frederix ◽  
Ioannis Tsinikos
Keyword(s):  
Matrix Element ◽  
Transverse Momentum ◽  
Cross Section ◽  
Parton Shower ◽  
Inclusive Cross Section ◽  
Tree Level ◽  
Spin Correlations ◽  
Narrow Width Approximation ◽  
Merging Procedure ◽  
Narrow Width

Abstract We introduce an improvement to the FxFx matrix element merging procedure for pp →$$ t\overline{t}W $$ t t ¯ W production at NLO in QCD with one and/or two additional jets. The main modification is an improved treatment of jets that are not logarithmically enhanced in the low transverse-momentum regime. We provide predictions for the inclusive cross section and the $$ t\overline{t}W $$ t t ¯ W differential distributions including parton-shower effects. Taking also the NLO EW corrections into account, this results in the most-accurate predictions for this process to date. We further proceed to include the on-shell LO decays of the $$ t\overline{t}W $$ t t ¯ W including the tree-level spin correlations within the narrow-width approximation, focusing on the multi-lepton signatures studied at the LHC. We find a ∼30% increase over the NLO QCD prediction and large non-flat K-factors to differential distributions.

scholarly journals The role of colour flows in matrix element computations and Monte Carlo simulations

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Stefano Frixione ◽  
Bryan R. Webber
Keyword(s):  
Monte Carlo ◽  
Matrix Element ◽  
Monte Carlo Simulations ◽  
Closed Form ◽  
Parton Shower ◽  
Natural Generalization ◽  
Tree Level ◽  
Matrix Elements ◽  
Soft Radiation

Abstract We discuss how colour flows can be used to simplify the computation of matrix elements, and in the context of parton shower Monte Carlos with accuracy beyond leading-colour. We show that, by systematically employing them, the results for tree-level matrix elements and their soft limits can be given in a closed form that does not require any colour algebra. The colour flows that we define are a natural generalization of those exploited by existing Monte Carlos; we construct their representations in terms of different but conceptually equivalent quantities, namely colour loops and dipole graphs, and examine how these objects may help to extend the accuracy of Monte Carlos through the inclusion of subleading-colour effects. We show how the results that we obtain can be used, with trivial modifications, in the context of QCD+QED simulations, since we are able to put the gluon and photon soft-radiation patterns on the same footing. We also comment on some peculiar properties of gluon-only colour flows, and their relationships with established results in the mathematics of permutations.

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