scholarly journals IR-improved DGLAP parton shower effects for associated production of a W boson and jets in pp collisions at s = 8 and 13 TeV

2020 ◽  
Vol 35 (32) ◽  
pp. 2050197
Author(s):  
B. Shakerin ◽  
B. F. L. Ward
Keyword(s):  
Matrix Element ◽  
Energy Dependence ◽  
Cross Sections ◽  
Parton Shower ◽  
W Boson ◽  
Exact Formula ◽  
Leading Order ◽  
Angular Correlations ◽  
Associated Production ◽  
Theoretical Predictions

In a previous paper, hereafter referred to as I, we have analyzed the 7 TeV LHC data on [Formula: see text] events from the standpoint of IR-improved DGLAP parton shower effects, using the IR-improved Herwiri1.031 parton shower MC in comparison with the Herwig6.5 parton shower MC in the context of the exact [Formula: see text] matrix element matched parton shower framework provided by MG5_aMC@NLO. In this paper, we extend this analysis to the LHC 8 and 13 TeV data to investigate the energy dependence of the results obtained in I. Specifically, [Formula: see text] events are generated in the MADGRAPH5_aMC@NLO framework and showered by HERWIG6.521 and HERWIRI1.031 with [Formula: see text] and 0 GeV, respectively. The differential cross sections are reported as functions of jet multiplicity, transverse linear momenta [Formula: see text], the jet pseudorapidity [Formula: see text] and the scalar sum of jet transverse momenta [Formula: see text] for different jet multiplicities 1–3. The dijet cross sections as functions of transverse linear momenta, invariant mass of the dijet and the jet separation are shown as well. Distributions of angular correlations between the jets and the muon are examined as well and the corresponding cross sections are presented. The respective measured cross sections are compared with the exact next-to-leading-order (NLO) matrix element matched parton shower theoretical predictions provided by MADGRAPH5_aMC@NLO/HERWIRI1.031 [Formula: see text] and MADGRAPH5_aMC@NLO/HERWIG6.521 [Formula: see text] and the phenomenological consequences are discussed with an eye toward their energy dependence.

scholarly journals Production of prompt photons associated with jets at LHC in kT-factorization

2019 ◽  
Vol 222 ◽  
pp. 03015
Author(s):  
Maxim Malyshev ◽  
Artem Lipatov ◽  
Hannes Jung
Keyword(s):  
Monte Carlo ◽  
Cross Sections ◽  
Parton Shower ◽  
Gluon Fusion ◽  
Monte Carlo Generator ◽  
Hadronic Jets ◽  
Factorization Approach ◽  
Associated Production ◽  
Parton Showering ◽  
Collinear Limit

We use the kT–factorization approach to calculate total and differential cross sections of associated production of prompt photons and hadronic jets at the LHC energies. Our consideration relies on the pegasus Monte-Carlo generator with implemented ℴ(αα2s) off-shell gluon–gluon fusion subprocess g*g* → γqq− and several subleading quark-initiated contributions from ℴ(ααs) and ℴ(αα2s) subprocesses, taken into account in the collinear limit. Using Monte-Carlo generators CASCADE and PYTHIA, we investigate parton showering effects and compare our predictions with the data, taken by CMS and ATLAS collaborations at the LHC. We demostrate reasonabledescription of the data and the importance of parton shower effects in the kT–factorization.

scholarly journals An event generator for same-sign W-boson scattering at the LHC including electroweak corrections

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Mauro Chiesa ◽  
Ansgar Denner ◽  
Jean-Nicolas Lang ◽  
Mathieu Pellen
Keyword(s):  
Monte Carlo ◽  
Matrix Element ◽  
Parton Shower ◽  
W Boson ◽  
Event Generator ◽  
Monte Carlo Program ◽  
The Matrix ◽  
Electroweak Corrections

Abstract In this article we present an event generator based on the Monte Carlo program Powheg in combination with the matrix-element generator Recola. We apply it to compute NLO electroweak corrections to same-sign W-boson scattering, which have been shown to be large at the LHC. The event generator allows for the generation of unweighted events including the effect of the NLO electroweak corrections matched to a QED parton shower and interfaced to a QCD parton shower. In view of the expected experimental precision of future measurements, the use of such a tool will be indispensable.

Implementation of the ATLAS-EXOT-2018-030 analysis in the MadAnalysis 5 framework (W′ boson into a lepton and a neutrino; 139 fb−1)

2020 ◽  
pp. 2141001
Author(s):  
Kyungmin Park ◽  
Ui Min ◽  
Soo Jin Lee ◽  
Won Jun
Keyword(s):  
Transverse Momentum ◽  
Cross Sections ◽  
Charged Lepton ◽  
W Boson ◽  
Transverse Mass ◽  
Pole Mass ◽  
Leading Order ◽  
Mass Distributions ◽  
Signal Prediction ◽  
Missing Transverse Momentum

We present the MadAnalysis 5 implementation of the heavily charged gauge boson search to recast the analysis of its decay into one charged lepton and missing transverse momentum. Signal events describing [Formula: see text] ([Formula: see text] or [Formula: see text]) at [Formula: see text] TeV in the sequential standard model are generated by the MadGraph5_aMC@NLO at leading order. The corresponding signal cross-sections for both electron and muon channels vary from 195 fb to 0.238 fb depending on the pole mass of the [Formula: see text] boson in the range of 2 TeV to 6 TeV. We validate our implementation by comparing the transverse mass distributions of our signal prediction to those of the ATLAS analysis for an integrated luminosity of 139 fb[Formula: see text].

scholarly journals Multiplicative-accumulative matching of NLO calculations with parton showers

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Paolo Nason ◽  
Gavin P. Salam
Keyword(s):  
Phase Space ◽  
Matrix Element ◽  
Parton Shower ◽  
Leading Order ◽  
Positive Weight ◽  
New Approach ◽  
The Matrix ◽  
Core Features

Abstract We propose a new approach for combining next-to-leading order (NLO) and parton shower (PS) calculations so as to obtain three core features: (a) applicability to general showers, as with the MC@NLO and POWHEG methods; (b) positive-weight events, as with the KrkNLO and POWHEG methods; and (c) all showering attributed to the parton shower code, as with the MC@NLO and KrkNLO methods. This is achieved by using multiplicative matching in phase space regions where the shower overestimates the matrix element and accumulative (additive) matching in regions where the shower underestimates the matrix element, an approach that can be viewed as a combination of the MC@NLO and KrkNLO methods.

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 Curing the unphysical behaviour of NLO quarkonium production at the LHC and its relevance to constrain the gluon PDF at low scales

2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Jean-Philippe Lansberg ◽  
Melih A. Ozcelik
Keyword(s):  
Energy Dependence ◽  
Cross Sections ◽  
Wide Class ◽  
Particle Physics ◽  
Local Minimum ◽  
Leading Order ◽  
Scalar Boson ◽  
Quarkonium Production

AbstractWe address the unphysical energy dependence of quarkonium-hadroproduction cross sections at Next-to-Leading Order (NLO) in $$\alpha _s$$ α s which we attribute to an over-subtraction in the factorisation of the collinear singularities inside the PDFs in the $$\overline{\text {MS}}$$ MS ¯ scheme. Such over- or under-subtractions have a limited phenomenological relevance in most of the scattering processes in particle physics. On the contrary, it is particularly harmful for $$P_T$$ P T -integrated charmonium hadroproduction which renders a wide class of NLO results essentially unusable. Indeed, in such processes, $$\alpha _s$$ α s is not so small, the PDFs are not evolved much and can be rather flat for the corresponding momentum fractions and, finally, some process-dependent NLO pieces are either too small or too large. We propose a scale-fixing criterion which avoids such an over-subtraction. We demonstrate its efficiency for $$\eta _{c,b}$$ η c , b but also for a fictitious light elementary scalar boson. Having provided stable NLO predictions for $$\eta _{c,b}$$ η c , b $$P_T$$ P T -integrated cross sections, $$\sigma ^{\mathrm{NLO}}_{\eta _Q}$$ σ η Q NLO , and discussed the options to study $$\eta _{b}$$ η b hadroproduction, we argue that their measurement at the LHC can help better determine the gluon PDF at low scales and tell whether the local minimum in conventional NLO gluon PDFs around $$x=0.001$$ x = 0.001 at scales below 2 GeV is physical or not.

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