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 A factorisation-aware Matrix element emulator

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
D. Maître ◽  
H. Truong
Keyword(s):  
Neural Network ◽  
Phase Space ◽  
Matrix Element ◽  
Percent Level ◽  
Matrix Elements ◽  
Leading Order ◽  
Jet Production ◽  
The Neural Network ◽  
The Matrix ◽  
The One

Abstract In this article we present a neural network based model to emulate matrix elements. This model improves on existing methods by taking advantage of the known factorisation properties of matrix elements. In doing so we can control the behaviour of simulated matrix elements when extrapolating into more singular regions than the ones used for training the neural network. We apply our model to the case of leading-order jet production in e+e− collisions with up to five jets. Our results show that this model can reproduce the matrix elements with errors below the one-percent level on the phase-space covered during fitting and testing, and a robust extrapolation to the parts of the phase-space where the matrix elements are more singular than seen at the fitting stage.

scholarly journals The matrix element method at next-to-leading order

2012 ◽  
Vol 2012 (11) ◽  
Author(s):  
John M. Campbell ◽  
Walter T. Giele ◽  
Ciaran Williams
Keyword(s):  
Matrix Element ◽  
Leading Order ◽  
Matrix Element Method ◽  
The Matrix ◽  
Element Method

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.

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 Towards colour flow evolution at two loops

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Simon Plätzer ◽  
Ines Ruffa
Keyword(s):  
Phase Space ◽  
Parton Shower ◽  
Soft Gluon ◽  
Leading Order ◽  
Colour Flow ◽  
Flow Evolution ◽  
Dipole Picture

Abstract We calculate the two-loop and one-loop/one-emission contributions required for soft gluon evolution at the next-to-leading order. The colour structures are expressed in the colour flow basis, and the kinematic dependence and loop integrals are expressed in terms of multiple cuts and phase-space-like integrals. This directly allows to use them in the resummation of non-global observables and improved parton shower algorithms beyond the leading order and beyond the leading colour limit. Within the colour flow basis it becomes apparent that correlations beyond a dipole picture emerge even in colour-diagonal elements of the virtual corrections.

scholarly journals Finding the Higgs boson in decays toZγusing the matrix element method at next-to-leading order

2013 ◽  
Vol 87 (7) ◽  
Author(s):  
John M. Campbell ◽  
R. Keith Ellis ◽  
Walter T. Giele ◽  
Ciaran Williams
Keyword(s):  
Higgs Boson ◽  
Matrix Element ◽  
Leading Order ◽  
Matrix Element Method ◽  
The Matrix ◽  
Element Method
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