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We present the MCscales approach for incorporating scale uncertainties in parton distribution functions (PDFs). The new methodology builds on the Monte Carlo sampling for propagating experimental uncertainties into the PDF space that…

High Energy Physics - Phenomenology · Physics 2023-03-27 Zahari Kassabov , Maria Ubiali , Cameron Voisey

I show that with simple extensions of the shower algorithms in Monte Carlo programs, one can implement NLO corrections to the hardest emission that overcome the problems of negative weighted events found in previous implementations. Simple…

High Energy Physics - Phenomenology · Physics 2011-05-05 Paolo Nason

We present NNPDF4.0MC, a variant of the NNPDF4.0 set of parton distributions (PDFs) at LO, NLO and NNLO, with and without inclusion of the photon PDF, suitable for use with Monte Carlo (MC) event generators, which require PDFs to satisfy…

High Energy Physics - Phenomenology · Physics 2024-08-29 Juan Cruz-Martinez , Stefano Forte , Niccolo Laurenti , Tanjona R. Rabemananjara , Juan Rojo

When the initial state evolution of a parton shower is organized according to the standard "backward evolution'' prescription, ratios of parton distribution functions appear in the splitting probabilities. The shower thus organized evolves…

High Energy Physics - Phenomenology · Physics 2015-06-18 Zoltan Nagy , Davison E. Soper

We present a solution of the DGLAP evolution equations, written in terms of Sudakov form factors to describe the branching and no-branching probabilities, using a parton branching Monte Carlo method. We demonstrate numerically that this…

High Energy Physics - Phenomenology · Physics 2017-10-12 Aleksandra Lelek

In this paper, we discuss the algorithms used in the LO evolution program for nondiagonal parton distributions in the DGLAP region and discuss the stability of the code. Furthermore, we demonstrate that we can reproduce the case of the LO…

High Energy Physics - Phenomenology · Physics 2007-05-23 Andreas Freund , Vadim Guzey

In this article, we present a Next-to-Leading Order (NLO) QCD analysis to study the role and influence of different schemes on simultaneous determination of the Parton Distribution Functions (PDFs) and strong coupling, $\alpha_s(M^2_Z)$. We…

High Energy Physics - Phenomenology · Physics 2017-09-26 A. Vafaee , A. N. Khorramian

In this review, we present a new method for computing physical cross sections at NLO accuracy in QCD without using the standard Dimensional Regularisation. The algorithm is based on the Loop-Tree Duality theorem, which allow us to obtain…

High Energy Physics - Phenomenology · Physics 2016-11-23 R. J. Hernández-Pinto , F. Driencourt-Mangin , G. Rodrigo , G. F. R. Sborlini

Polarized parton distributions and structure functions of the nucleon are analyzed in the improved valon model. The valon representation provides a model to represent hadrons in terms of quarks, providing a unified description of bound…

High Energy Physics - Phenomenology · Physics 2009-11-10 Ali N. Khorramian , A. Mirjalili , S. Atashbar Tehrani

We explore connections between two common methods for quantifying the uncertainty in parton distribution functions (PDFs), based on the Hessian error matrix and Monte-Carlo sampling. CT14 parton distributions in the Hessian representation…

High Energy Physics - Phenomenology · Physics 2017-04-05 Tie-Jiun Hou , Jun Gao , Joey Huston , Pavel Nadolsky , Carl Schmidt , Daniel Stump , Bo-Ting Wang , Ke-Ping Xie , Sayipjamal Dulat , Jon Pumplin , C. -P. Yuan

We present a new general algorithm for calculating arbitrary jet cross sections in arbitrary scattering processes to next-to-leading accuracy in perturbative QCD. The algorithm is based on the subtraction method. The key ingredients are new…

High Energy Physics - Phenomenology · Physics 2009-10-28 Stefano Catani , Michael H. Seymour

The scale evolution of parton distributions is governed by splitting functions. We compute the four-loop splitting functions in perturbative QCD that control the evolution of quark non-singlet distributions. We confirm previous partial…

High Energy Physics - Phenomenology · Physics 2026-04-27 Thomas Gehrmann , Andreas von Manteuffel , Vasily Sotnikov , Tong-Zhi Yang

We discuss the problem of incorporating recoil effects into the probabilistic QCD evolution scheme based on the picture of colour dipoles as done in recent Monte Carlo programs. Such a scheme correctly describes subleading soft…

High Energy Physics - Phenomenology · Physics 2009-03-27 Yu. L. Dokshitzer , G. Marchesini

We complete the construction of the non-forward evolution kernels in next-to-leading order responsible for the scale dependence of e.g. parity even singlet distribution amplitudes. Our formalism is designed to avoid any explicit two-loop…

High Energy Physics - Phenomenology · Physics 2009-10-31 A. V. Belitsky , D. Müller

Using QCD motivated and phenomenological considerations, we construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and…

High Energy Physics - Phenomenology · Physics 2014-11-17 Lionel E. Gordon , Mehrdad Goshtasbpour , Gordon P. Ramsey

We present the first complete result for the next-to-next-to-leading order (NNLO) hard matching kernel indispensable for a precision extraction of light meson distribution amplitudes from lattice calculations of equal-time nonlocal…

High Energy Physics - Phenomenology · Physics 2025-04-15 Yao Ji , Fei Yao , Jian-Hui Zhang

The parton distributions functions (PDFs) derived from the NNLO QCD analysis of existing light-targets deep-inelastic-scattering data are presented. The NLO and NNLO PDFs are compared in order to analyze perturbative stability of the…

High Energy Physics - Phenomenology · Physics 2007-05-23 S. Alekhin

We match next-to-leading order QCD results for single-top hadroproduction with parton shower Monte Carlo simulations, according to the prescription of the MC@NLO formalism. In this way, we achieve the first practical implementation in…

High Energy Physics - Phenomenology · Physics 2009-11-11 S. Frixione , E. Laenen , P. Motylinski , B. R. Webber

We study the mixed effect of QCD and QED corrections to the evolution of parton distribution functions (PDFs). The Altarelli-Parisi splitting functions are extended to one order higher in QED, reaching ${\cal O}(\alpha \, \alpha_S^2)$…

High Energy Physics - Phenomenology · Physics 2016-11-16 German F. R. Sborlini , Daniel de Florian , German Rodrigo

Double parton distributions (DPDs) receive a short-distance contribution from a single parton splitting to yield the two observed partons. We investigate this mechanism at next-to-leading order (NLO) in perturbation theory. Technically, we…

High Energy Physics - Phenomenology · Physics 2019-08-07 Markus Diehl , Jonathan R. Gaunt , Peter Ploessl , Andreas Schafer