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Foundations of Perturbative QCD

01 Nov 2013-
TL;DR: In this paper, a systematic treatment of perturbative QCD is given, giving an accurate account of the concepts, theorems and their justification, giving strong motivations for the methods.
Abstract: The most non-trivial of the established microscopic theories of physics is QCD: the theory of the strong interaction. A critical link between theory and experiment is provided by the methods of perturbative QCD, notably the well-known factorization theorems. Giving an accurate account of the concepts, theorems and their justification, this book is a systematic treatment of perturbative QCD. As well as giving a mathematical treatment, the book relates the concepts to experimental data, giving strong motivations for the methods. It also examines in detail transverse-momentum-dependent parton densities, an increasingly important subject not normally treated in other books. Ideal for graduate students starting their work in high-energy physics, it will also interest experienced researchers wanting a clear account of the subject.
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Journal ArticleDOI
TL;DR: A comprehensive review of state-of-the-art theoretical and machine learning developments in jet substructure is provided in this article, which is meant both as a pedagogical introduction and as a comprehensive reference for experts.

340 citations

Journal ArticleDOI
TL;DR: In this paper, the EMC effect for valence quarks, a reduction in the Deep Inelastic Scattering (DIS) cross-section ratios for nuclei relative to deuterium, and its possible connection to nucleon-nucleon Short-Range Correlations (SRC) in nuclei are discussed.
Abstract: This article reviews our current understanding of how the internal quark structure of a nucleon bound in nuclei differs from that of a free nucleon. We focus on the interpretation of measurements of the EMC effect for valence quarks, a reduction in the Deep Inelastic Scattering (DIS) cross-section ratios for nuclei relative to deuterium, and its possible connection to nucleon-nucleon Short-Range Correlations (SRC) in nuclei. Our review and new analysis (involving the amplitudes of non-nucleonic configurations in the nucleus) of the available experimental and theoretical evidence shows that there is a phenomenological relation between the EMC effect and the effects of SRC that is not an accident. The influence of strongly correlated neutron-proton pairs involving highly virtual nucleons is responsible for both effects. These correlated pairs are temporary high-density fluctuations in the nucleus in which the internal structure of the nucleons is briefly modified. This conclusion needs to be solidified by the future experiments and improved theoretical analyses that are discussed herein.

260 citations


Cites background from "Foundations of Perturbative QCD"

  • ...of = 0:04 was sucient to reproduce the early EMC data. However, we will show that the ideas of shifting the value of xAbased on binding energy or separation energy considerations violates rigorous (Collins, 2013) baryon and momentum sum rules, and therefore cannot be a viable explanation of the EMC eect. Consider a nuclear model in which nucleons are the only degrees of freedom. There will be a conserved bar...

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Journal ArticleDOI
TL;DR: In this article, a comprehensive analysis and extraction of the unpolarized transverse momentum dependent (TMD) parton distribution functions, which are fundamental constituents of the TMD factorization theorem, is presented.
Abstract: We present a comprehensive analysis and extraction of the unpolarized transverse momentum dependent (TMD) parton distribution functions, which are fundamental constituents of the TMD factorization theorem. We provide a general review of the theory of TMD distributions, and present a new scheme of scale fixation. This scheme, called the zeta-prescription, allows to minimize the impact of perturbative logarithms in a large range of scales and does not generate undesired power corrections. Within zeta-prescription we consistently include the perturbatively calculable parts up to next-to-next-to-leading order (NNLO), and perform the global fit of the Drell-Yan and Z-boson production, which include the data of E288, Tevatron and LHC experiments. The non-perturbative part of the TMDs are explored checking a variety of models. We support the obtained results by a study of theoretical uncertainties, perturbative convergence, and a dedicated study of the range of applicability of the TMD factorization theorem. The considered non-perturbative models present significant differences in the fitting behavior, which allow us to clearly disfavor most of them. The numerical evaluations are provided by the arTeMiDe code, which is introduced in this work and that can be used for current/future TMD phenomenology.

132 citations


Cites background from "Foundations of Perturbative QCD"

  • ...2 TMD parton distributions: evolution The quark unpolarized TMDPDFs are given by the matrix element [1, 2, 11]...

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  • ...Indeed, the first typical step is to fix ζ = C(2) 0/b(2), or ζ = μ(2) [1, 12, 52]....

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Journal ArticleDOI
TL;DR: In this paper, the authors consider semi-inclusive deep inelastic scattering (SIDIS) and Drell-Yan events within transverse momentum dependent (TMD) factorization and extract the unpolarized TMD distributions and the non-perturbative evolution kernel.
Abstract: We consider semi-inclusive deep inelastic scattering (SIDIS) and Drell-Yan events within transverse momentum dependent (TMD) factorization. Based on the simultaneous fit of multiple data points, we extract the unpolarized TMD distributions and the non-perturbative evolution kernel. The high quality of the fit confirms a complete universality of TMD non-perturbative distributions. The extraction is supplemented by phenomenological analyses of various parts of the TMD factorization, such as sensitivity to non-perturbative parameterizations, perturbative orders, collinear distributions, correlations between parameters, and others.

129 citations

Journal ArticleDOI
TL;DR: The field of fragmentation functions of light quarks and gluons is reviewed in this paper, where the dependence of the fragmentation functions on transverse momenta and on polarization degrees of freedom is examined.

124 citations


Cites background or methods from "Foundations of Perturbative QCD"

  • ...On the other hand, if one first regularizes the light-cone singularities of TMD FFs, and afterwards performs the kT integration one no longer has simple relations of the type (41)-(43) — see for instance [88, 12]....

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  • ...When taking into account higher-order QCD effects this parton model interpretation of FFs gets distorted [12]....

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  • ...Moreover, we have suppressed the dependence of ∆ on a renormalization scale μ, which is caused by the renormalization of the two quark field operators and a divergence arising from the integration upon the transverse quark momentum [12]....

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  • ...They can be specified through the gluon-gluon (gg) fragmentation correlator [10, 68, 12] ∆(z;Ph, Sh) = ∑...

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  • ...) In the case of a quark with flavor q fragmenting into a hadron h the field-theoretic expression of the fragmentation correlator reads [10, 65, 67, 12]...

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