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Abe, K.; Akagi, T.; Anderson, B. D.; Anthony, P.L.; Arnold, R. G.; Averett, T.; Band, H. R.; Berisso, C.M.; Bogorad, P.; Borel, H.; Bosted, P.; Breton, Vincent; Buénerd, M.; Cates, G. D.; Chupp, T. E.; Churchwell, S.; Coulter, K. P.; Daoudi, M.; Decowski, P.; Erickson, R.; Fellbaum, J.; Fonvieille, H.; Gearhart, R.; Ghazikhanian, V.; Griffioen, K. A.; Hicks, R. S.; Holmes, R.; Hughes, E. W.; Igo, G.; Incerti, S.; Johnson, J. R.; Kahl, W.; Khayat, M.; Kolomensky, Yu. G.; Kuhn, S. E.; Kumar, Krishna; Kuriki, M.; Lombard-Nelsen, R. M.; Manley, D. M.; Marroncle, J.; Maruyama, T.; Marvin, T.; Meyer, W.; Meziani, Z. E.; Miller, Donald H.; Mitchell, G. S.; Olson, M.; Peterson, G. A.; Petratos, G. G.; Pitthan, R.; Prepost, R.; Raines, P.; Raue, B. A.; Reyna, D.; Rochester, L.S.; Rock, S. E.; Romalis, Michael; Sabatié, F.; Shapiro, G.; Shaw, J.; Smith, T. B.; Sorrell, L.; Souder, P. A.; Staley, F.; Lorant, S. St.; Stuart, L. M.; Suekane, F.; Szalata, Z. M.; Terrien, Y.; Thompson, A. K.; Toole, T.; Wang, X.; Watson, J. W.; Welsh, Robert C.; Wesselmann, F. R.; Wright, T.; Young, C.; Youngman, B.; Yuta, H.; Zhang, W. M.; Żyla, P.

doi:10.1103/physrevlett.79.26

Cited by 342 publications

(160 citation statements)

References 45 publications

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“…The blue data points are from Jlab [190], the green points are from Hermes [183], the black points are from Fermilab [78], the red points are from CERN [186] and the magenta points are from SLAC [179,181,182,184].…”

Section: Effective Chargesmentioning

confidence: 99%

The QCD running coupling

Deur

Brodsky

Téramond

2016

Progress in Particle and Nuclear Physics

271

228

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We review the present theoretical and empirical knowledge for α s , the fundamental coupling underlying the interactions of quarks and gluons in Quantum Chromodynamics (QCD). The dependence of α s (Q 2 ) on momentum transfer Q encodes the underlying dynamics of hadron physics -from color confinement in the infrared domain to asymptotic freedom at short distances. We review constraints on α s (Q 2 ) at high Q 2 , as predicted by perturbative QCD, and its analytic behavior at small Q 2 , based on models of nonperturbative dynamics. In the introductory part of this review, we explain the phenomenological meaning of the coupling, the reason for its running, and the challenges facing a complete understanding of its analytic behavior in the infrared domain.In the second, more technical, part of the review, we discuss the behavior of α s (Q 2 ) in the high momentum transfer domain of QCD. We review how α s is defined, including its renormalization scheme dependence, the definition of its renormalization scale, the utility of effective charges, as well as "Commensurate Scale Relations" which connect the various definitions of the QCD coupling without renormalization-scale ambiguity. We also report recent significant measurements and advanced theoretical analyses which have led to precise QCD predictions at high energy. As an example of an important optimization procedure, we discuss the "Principle of Maximum Conformality", which enhances QCD's predictive power by removing the dependence of the predictions for physical observables on the choice of theoretical conventions such as the renormalization scheme. In the last part of the review, we discuss the challenge of understanding the analytic behavior α s (Q 2 ) in the low momentum transfer domain. We survey various theoretical models for the nonperturbative strongly coupled regime, such as the light-front holographic approach to QCD. This new framework predicts the form of the quark-confinement potential underlying hadron spectroscopy and dynamics, and it gives a remarkable connection between the perturbative QCD scale Λ and hadron masses. One can also identify a specific scale Q 0 which demarcates the division between perturbative and nonperturbative QCD. We also review other important methods for computing the QCD coupling, including lattice QCD, the Schwinger-Dyson equations and the GribovZwanziger analysis. After describing these approaches and enumerating their conflicting predictions, we discuss the origin of these discrepancies and how to remedy them. Our aim is not only to review the advances in this difficult area, but also to suggest what could be an optimal definition of α s (Q 2 ) in order to bring better unity to the subject.2

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Section: Effective Chargesmentioning

confidence: 99%

The QCD running coupling

Deur

Brodsky

Téramond

2016

Progress in Particle and Nuclear Physics

271

228

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“…Inclusive events were measured in two new single-arm spectrometers. The resulting measurements covered a kinematic range of 0.014 < x < 0.7 and 1.2 < Q 2 < 15.0 (GeV/c) 2 [52].…”

Section: : Measurements and Models 45mentioning

confidence: 99%

Measurements of the Double-Spin Asymmetry A<sub>1</sub> on Helium-3: Toward a Precise Measurement of the Neutron A<sub>1</sub>

Parno

2011

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The spin structure of protons and neutrons has been an open question for nearly twenty-five years, after surprising experimental results disproved the simple model in which valence quarks were responsible for nearly 100% of the nucleon spin. Diverse theoretical approaches have been brought to bear on the problem, but a shortage of precise data -especially on neutron spin structure -has prevented a thorough understanding.Experiment E06-014, conducted in Hall A of Jefferson Laboratory in 2009, presented an opportunity to add to the world data set for the neutron in the poorly covered valence-quark region. Jefferson Laboratory's highly polarized electron beam, combined with Hall A's facilities for a high-density, highly polarized 3 He target, allowed a high-luminosity double-polarized experiment, while the large acceptance of the BigBite spectrometer gave coverage over a wide kinematic range: 0.15 < x < 0.95. In this work, we present the analysis of a portion of the E06-014 data, measured with an incident beam energy of 4.74 GeV and spanning 1.5 < Q 2 < 5.5 (GeV/c) 2 . From these data, we extract the longitudinal asymmetry in virtual photon-nucleon scattering, A 1 , on the 3 He nucleus. Combined with the remaining E06-014 data, this will form the basis of a measurement of the neutron asymmetry A n 1 that will extend the kinematic range of the data available to test models of spin-dependent parton distributions in the nucleon. AcknowledgmentsNo one in this age can earn a physics PhD based solely on her own work and study; the making of a doctor, like the making of a modern particle-physics experiment, requires the goodwill and support of many. In my own life and studies, I have been profoundly blessed by the presence of my family, friends, and colleagues. It is traditional to thank these wonderful people in these pages, as though words were enough. They aren't, but they are a start.My parents, Christine Marwick and Richard Seymour, brought me up to have both a deep curiosity about the world and the work ethic I needed to answer my own questions. The love of language my mother gave me made writing this dissertation far less painful than it might have been; my father urged me to take my first voluntary science course and then kindly refrained from saying "I told you so" at the sudden fascination with physics that resulted. My not-so-little brother, Matthew, kept me honest with everything I did.The love and support of my extended family has been invaluable. My grandparents, Bob and Dolores Marwick, generously funded my undergraduate education. They and my aunts, uncles, and assorted cousins, scattered around the continent, taught me that I could find something of home wherever I am. To Rob and Ann Marwick, Mike and Monica Marwick, Lorrie Marwick and Guy Marsh, Nancy and Don DeMuth, and Josephine Marwick, thank you for the delicious meals, the fascinating conversations and your willingness to talk physics. To my beloved cousins, thank you for everything. Growing up, I was also lucky to enjoy the love of many peo...

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“…However these same traces can be also expressed through the LF spectral function, since from Eqs. (16,17) one has…”

Section: The J = 1/2 Lf Spectral Function and The Nucleon Lf Tmdsmentioning

confidence: 99%

“…Ref. [17]). The nuclear effects are hidden in the proton and neutron "effective polarizations", p p(n) .…”

Section: Polarized 3 He Target As a Polarized Neutron Targetmentioning

confidence: 99%

Transverse momentum distributions and nuclear effects

Pace

Dotto

Kaptari

et al. 2015

EPJ Web of Conferences

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Abstract. A distorted spin-dependent spectral function for 3 He is considered to take care of the final state interaction in the extraction of the quark transverse-momentum distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3 He at finite momentum transfers. The generalization of the analysis in a Poincaré covariant framework within the light-front dynamics is outlined. The definition of the light-front spin-dependent spectral function for a J=1/2 system, as the nucleon, allows us to show that within the light-front dynamics and in the valence approximation only three of the six leading twist T-even transversemomentum distributions are independent.

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Precision Determination of the Neutron Spin Structure Functiong1n

Cited by 342 publications

References 45 publications

The QCD running coupling

The QCD running coupling

Measurements of the Double-Spin Asymmetry A<sub>1</sub> on Helium-3: Toward a Precise Measurement of the Neutron A<sub>1</sub>

Transverse momentum distributions and nuclear effects

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