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Experimental Determination of the Effective Strong Coupling Constant

Experimental Determination of the Effective Strong Coupling Constant
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Release: 2005
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We extract an effective strong coupling constant from low Q2 data on the Bjorken sum. Using sum rules, we establish its Q2-behavior over the complete Q2-range. The result is compared to effective coupling constants extracted from different processes and to calculations based on Schwinger-Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constant and the calculations is not clear, the results agree surprisingly well.


Experimental Determination of an Effective Coupling Constant

Experimental Determination of an Effective Coupling Constant
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Release: 2004
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Quantum chromodynamics (QCD), the theory of the strong force, describes the interactions of two basic building blocks of matter: quarks and gluons. High precision data taken at the Jefferson Lab electron accelerator provide a solid basis for the detailed study of many aspects of QCD. The accelerator's beam energy permits investigations of the transition between the short distance and long distance regimes of the strong force. Understanding how the descriptions of these regimes are related is essential in comprehending the structure of ordinary matter. Using new data from polarized electron - nucleon scattering, we extract the scale dependence of an effective strong coupling constant, $\alpha_{\rm{s}}^{\rm{eff}}$. Our result shows that this effective charge freezes, i.e. loses its scale dependence, at long (nucleon-size) distances. This finite behavior allows us to obtain a physical coupling constant for the strong interaction that is relevant at all scales.


Precision Determination of the Strong Coupling Constant

Precision Determination of the Strong Coupling Constant
Author: Riccardo Abbate
Publisher:
Total Pages: 223
Release: 2012
Genre:
ISBN:

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In this thesis we study the event shapes variable thrust. Event shape variables are observables that characterize the shape of the distribution of the final state particles of a reaction. We take advantage of the formalism of Soft Collinear Effective Theory (SCET), an effective theory of the strong interactions appropriate for describing energetic jets. We give a factorization theorem for the process e+e- to hadrons, valid in the whole range of thrust values. This factorization theorem resums large logarithms at the N3LL accuracy and contains the full O(a) result for the fixed order cross section. In order to be able to describe the whole range of thrust values, we define the profile functions, which are thrust-dependent factorization scales which smoothly interpolate between regions where resummation of large logarithms is important and where it is not. To determine non perturbative effects, we fit renormalon-free nonperturbative matrix elements of operators defined in field theory, Q1. We perform a global analysis to all available thrust data in the tail region, where a two parameter fit to a,(mz) and the first power correction Q1 suffices. We find cr(mz) = 0.1135 i (0.0002)expt ± (0.0005)hadr ± (0.0009)pert, with X2 /dof(= 485) = 0.91, where the displayed 1-sigma errors are the total experimental error, the hadronization uncertainty, and the perturbative theory uncertainty, respectively. Furthermore, we perform a global analysis to all available data on the first moment of the thrust distribution. This analysis is a partially independent check of the tail fit, in fact it probes different regions of the thrust distribution and the analysis of experimental systematic uncertainties was conducted independently with respect to the data for the distribution. We find a,(mz) = 0.1141 i (0.0004)exp ± (0.0014)hadr ± (0.0007)pert with X2/dof(= 45) = 1.33. We also consider pp collisions, in particular the Drell-Yan process. Here we calculate analytically the beam thrust logarithms of the relevant beam functions and of the coefficient function at O(a2). This is a necessary ingredient for the calculation of the nonsingular terms in resummed predictions.


On the Origin of Natural Constants

On the Origin of Natural Constants
Author: Hans Peter Good
Publisher: Walter de Gruyter GmbH & Co KG
Total Pages: 318
Release: 2018-10-22
Genre: Science
ISBN: 3110610485

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Just as the circle number π or the Euler constant e determines mathematics, fundamental constants of nature define the scales of the natural sciences. This book presents a new perspective by means of a few axioms and compares the resulting validity with experimental data. By the axiomatic approach Sommerfeld's mysterious fine-structure constant and Dirac's cosmic number are fixed as pure number constants. Thanks to these number constants, it is possible to calculate the value for the anomalous magnetic-moment of the electron in a simple way compared to QED calculations. With the same number constants it is also possible to calculate masses, partial lifetimes, magnetic-moments or charge radii of fundamental particles. The expressions used for the calculations, with few exceptions, yield values within the experimental error limits of the Particle Data Group. The author shows that the introduced number constants give even better predictions than the complicated QED calculations of today's doctrine. In the first part only experimental data from the literature for checking the postulates are used. In the second part the author explains electrical transport measurements with emergent behaviour, which were carried out in a professional environment.


Advances in Magnetic and Optical Resonance

Advances in Magnetic and Optical Resonance
Author: Warren S. Warren
Publisher: Elsevier
Total Pages: 409
Release: 1996-12-06
Genre: Science
ISBN: 0080526306

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Since 1965, Advances in Magnetic and Optical Resonance has provided researchers with timely expositions of fundamental new developments in the theory of, experimentation with, and application of magnetic and optical resonance.


Particle Symmetries

Particle Symmetries
Author: Max Chrétien
Publisher: CRC Press
Total Pages: 718
Release: 1966
Genre: Science
ISBN: 9780677107554

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Proceedings of the Conference on Continuous Advances in QCD 2004

Proceedings of the Conference on Continuous Advances in QCD 2004
Author: T. Gherghetta
Publisher: World Scientific
Total Pages: 603
Release: 2004
Genre: Science
ISBN: 9812560726

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This book contains articles on the latest research in QCD from some of the leading experts in the field. These are based on talks presented at the Continuous Advances in QCD 2004 workshop held at the William I Fine Theoretical Physics Institute.The book will be a useful reference source for graduate students and researchers in high energy physics.The proceedings have been selected for coverage in: ? Index to Scientific & Technical Proceedings? (ISTP? / ISI Proceedings)? Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)? CC Proceedings ? Engineering & Physical Sciences


Determination of the Strong Coupling Constant ([alpha][sub S] and a Test of Perturbative QCD Using W + Jets Processes in the D0 Detector

Determination of the Strong Coupling Constant ([alpha][sub S] and a Test of Perturbative QCD Using W + Jets Processes in the D0 Detector
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Release: 2005
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ISBN:

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The D0 experiment has accumulated data for a study of inclusive W production corresponding to a total integrated luminosity of 14.3 [plus-minus] 1.7 pb[sup [minus]1] during the 1992--1993 Fermilab Tevatron collider run. The total number of W [yields] e + [nu] candidates is 9770. The ratio of the number of W + 1 jet events to that of W + 0 jet events has been measured as a function of jet minimum E[sub T]. Using this ratio the strong coupling constant, [alpha][sub s] at Q[sup 2] = M[sub W][sup 2] is measured to be [alpha][sub s](M[sub W][sup 2]) = 0.124 [plus-minus] 0.005(stat) [plus-minus] 0.006(MC) [plus-minus] 0.008(theory)[sub [minus]0.022][sup +0.026](sys) or ([sub [minus]0.025][sup +0.028] combined) with a jet minimum E[sub T] of 25 GeV. A quantitative test of perturbative QCD has been made by comparing the experimentally measured ratio with the theoretical predictions. The theoretical predictions of the ratio in both the leading order and next-to-leading order are in good agreement with the measured ratio.


Nuclear Science Abstracts

Nuclear Science Abstracts
Author:
Publisher:
Total Pages: 988
Release: 1975-03
Genre: Nuclear energy
ISBN:

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NMR Crystallography

NMR Crystallography
Author: Robin K. Harris
Publisher: John Wiley & Sons
Total Pages: 523
Release: 2012-12-19
Genre: Science
ISBN: 1118587324

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The content of this volume has been added to eMagRes (formerly Encyclopedia of Magnetic Resonance) - the ultimate online resource for NMR and MRI. The term "NMR Crystallography" has only recently come into common usage, and even now causes raised eyebrows within some parts of the diffraction community. The power of solid-state NMR to give crystallographic information has considerably increased since the CPMAS suite of techniques was introduced in 1976. In the first years of the 21st century, the ability of NMR to provide information to support and facilitate the analysis of single-crystal and powder diffraction patterns has become widely accepted. Indeed, NMR can now be used to refine diffraction results and, in favorable cases, to solve crystal structures with minimal (or even no) diffraction data. The increasing ability to relate chemical shifts (including the tensor components) to the crystallographic location of relevant atoms in the unit cell via computational methods has added significantly to the practice of NMR crystallography. Diffraction experts will increasingly welcome NMR as an allied technique in their structural analyses. Indeed, it may be that in the future crystal structures will be determined by simultaneously fitting diffraction patterns and NMR spectra. This Handbook is organised into six sections. The first contains an overview and some articles on fundamental NMR topics, followed by a section concentrating on chemical shifts, and one on coupling interactions. The fourth section contains articles describing how NMR results relate to fundamental crystallography concepts and to diffraction methods. The fifth section concerns specific aspects of structure, such as hydrogen bonding. Finally, four articles in the sixth section give applications of NMR crystallography to structural biology, organic & pharmaceutical chemistry, inorganic & materials chemistry, and geochemistry. About EMR Handbooks / eMagRes Handbooks The Encyclopedia of Magnetic Resonance (up to 2012) and eMagRes (from 2013 onward) publish a wide range of online articles on all aspects of magnetic resonance in physics, chemistry, biology and medicine. The existence of this large number of articles, written by experts in various fields, is enabling the publication of a series of EMR Handbooks / eMagRes Handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of articles from eMagRes. In consultation with the eMagRes Editorial Board, the EMR Handbooks / eMagRes Handbooks are coherently planned in advance by specially-selected Editors, and new articles are written (together with updates of some already existing articles) to give appropriate complete coverage. The handbooks are intended to be of value and interest to research students, postdoctoral fellows and other researchers learning about the scientific area in question and undertaking relevant experiments, whether in academia or industry. Have the content of this Handbook and the complete content of eMagRes at your fingertips! Visit: www.wileyonlinelibrary.com/ref/eMagRes View other eMagRes publications here