Recent progress in the understanding of single spin asymmetries

Metz, Andreas; Schlegel, Marc

doi:10.1002/andp.200410112

Cited by 12 publications

(12 citation statements)

References 42 publications

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“…Especially in the context of TMDs one should not underestimate the conceptual importance of model calculations. Model calculations demonstrated the existence of effects [261], paved the way towards an understanding of universality in the fragmentation process [395], established new TMDs [396,397], see [398] for a review. The distinction of T-even and T-odd TMDs is important also from the point of view of modeling.…”

Section: Non-perturbative Studies Of Tmds In Effective Approachesmentioning

confidence: 99%

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Gluons and the quark sea at high energies: distributions, polarization, tomography

Boer¹,

Diehl²,

Milner³

et al. 2011

198

291

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ForewordThe study of the fundamental structure of nuclear matter is a central thrust of physics research in the United States. As indicated in Frontiers of Nuclear Science, the 2007 Nuclear Science Advisory Committee long range plan, consideration of a future Electron-Ion Collider (EIC) is a priority and will likely be a significant focus of discussion at the next long range plan. We are therefore pleased to have supported the ten week program in fall 2010 at the Institute of Nuclear Theory which examined at length the science case for the EIC. This program was a major effort; it attracted the maximum allowable attendance over ten weeks.This report summarizes the current understanding of the physics and articulates important open questions that can be addressed by an EIC. It converges towards a set of "golden" experiments that illustrate both the science reach and the technical demands on such a facility, and thereby establishes a firm ground from which to launch the next phase in preparation for the upcoming long range plan discussions. We thank all the participants in this productive program. In particular, we would like to acknowledge the leadership and dedication of the five co-organizers of the program who are also the co-editors of this report.David Kaplan, Director, National Institute for Nuclear Theory Hugh Montgomery, Director, Thomas Jefferson National Accelerator Facility Steven Vigdor, Associate Lab Director, Brookhaven National Laboratory iii Preface This volume is based on a ten-week program on "Gluons and the quark sea at high energies", which took place at the Institute for Nuclear Theory (INT) in Seattle from September 13 to November 19, 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. Guiding questions were• What are the crucial science issues?• How do they fit within the overall goals for nuclear physics?• Why can't they be addressed adequately at existing facilities?• Will they still be interesting in the 2020's, when a suitable facility might be realized?The program started with a five-day workshop on "Perturbative and Non-Perturbative Aspects of QCD at Collider Energies", which was followed by eight weeks of regular program and a concluding four-day workshop on "The Science Case for an EIC".More than 120 theorists and experimentalists took part in the program over ten weeks. It was only possible to smoothly accommodate such a large number of participants because of the extraordinary efforts of the INT staff, to whom we extend our warm thanks and appreciation. We thank the INT Director, David Kaplan, for his strong support of the program and for covering a significant portion of the costs for printing this volume. We gratefully acknowledge additional financial support provided by BNL and JLab.The program w...

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Section: Non-perturbative Studies Of Tmds In Effective Approachesmentioning

confidence: 99%

“…The practical value of model results is that they can be used to predict new observables, or to guide educated Ansätze for fits of TMD parameterizations. [398] for a review. The distinction of T-even and T-odd TMDs is important also from the point of view of modeling.…”

mentioning

confidence: 99%

Gluons and the quark sea at high energies: distributions, polarization, tomography

Boer¹,

Diehl²,

Milner³

et al. 2011

198

291

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show abstract

“…Such perturbative calculations do not aim at providing a realistic model for the dynamics of the non-perturbative fragmentation process. Rather their importance is to indicate the existence of the mechanism [74]. It is therefore not surprizing to observe that the models [67][68][69][70][71] have difficulties to reproduce the quantitative properties and in particular the flavour dependence of H ⊥ 1 , though this could possibly be achieved by exploring the freedom in the choice of model parameters.…”

Section: Comparison To Model Calculations Of the Collins Functionmentioning

confidence: 99%

Collins effect in semiinclusive deeply inelastic scattering and in electron-positron-annihilation

2006

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1 Previously, the preliminary result [15] and longitudinal target SSA [28][29][30][31] data were used to extract H ⊥ 1 from SIDIS [32,33]. However, in these studies twist-3 effects [34] were not or only partially considered. Still earlier attempts to learn about the Collins effect from SSA in the hadronic processespp ↑ or pp ↑ → πX [35] were made in [36], but recent studies indicate that the Collins effect is not likely to be the dominant source of SSA in these processes [37] as it was assumed in [36].

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“…This makes the theoretical interpretation of data challenging, and motivates model studies to help to clarify the underlying physics. The important impact of model studies for the understanding of TMDs was reviewed in [24]. Model calculations also indicate that the status of TMD factorization in SIDIS beyond leading twist is not yet fully clarified [25].…”

Section: Introductionmentioning

confidence: 99%

Unpolarized transverse momentum dependent parton distribution functions beyond leading twist in quark models

Lorcé

Pasquini

Schweitzer

2015

J. High Energ. Phys.

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Higher-twist transverse momentum dependent parton distribution functions (TMDs) are a valuable probe of the quark-gluon dynamics in the nucleon, and play a vital role for the explanation of sizable azimuthal asymmetries in hadron production from unpolarized and polarized deep-inelastic lepton-nucleon scattering observed in experiments at CERN, DESY and Jefferson Lab. The associated observables are challenging to interpret, and still await a complete theoretical explanation, which makes guidance from models valuable. In this work we establish the formalism to describe unpolarized higher-twist TMDs in the light-front framework based on a Fock-space expansion of the nucleon state in terms of free on-shell parton states. We derive general expressions and present numerical results in a practical realization of this picture provided by the light-front constituent quark model. We review several other popular quark model approaches including free quark ensemble, bag, spectator and chiral quark-soliton model. We discuss how higher-twist TMDs are described in these models, and obtain results for several TMDs not discussed previously in literature. This study contributes to the understanding of non-perturbative properties of subleading twist TMDs. The results from the light-front constituent quark model are also compared to available phenomenological information, showing a satisfactory agreement.

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Recent progress in the understanding of single spin asymmetries

Cited by 12 publications

References 42 publications

Gluons and the quark sea at high energies: distributions, polarization, tomography

Gluons and the quark sea at high energies: distributions, polarization, tomography

Collins effect in semiinclusive deeply inelastic scattering and in electron-positron-annihilation

Unpolarized transverse momentum dependent parton distribution functions beyond leading twist in quark models

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