The spin structure of the proton

Bass, Steven D.

doi:10.1103/revmodphys.77.1257

Cited by 158 publications

(195 citation statements)

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“…Suggestions of possible δ-function contributions to PDFs were raised earlier [42,43] in discussions of the unpolarized Schwinger term and proton spin sum rules. The practical implication of the δ-function terms is to provide significantly greater flexibility in the allowed phenomenological parametrization of the s −s difference, suggesting that current forms used in global PDF analysis may be too restrictive.…”

Section: Introductionmentioning

confidence: 99%

Strange-quark asymmetry in the proton in chiral effective theory

Wang

Melnitchouk

et al. 2016

Phys. Rev. D

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We perform a comprehensive analysis of the strange-antistrange parton distribution function (PDF) asymmetry in the proton in the framework of chiral effective theory, including the full set of lowest order kaon loop diagrams with off-shell and contact interactions, in addition to the usual on-shell contributions previously discussed in the literature. We identify the presence of δ-function contributions to thes PDF at x = 0, with a corresponding valence-like component of the s-quark PDF at larger x, which allows greater flexibility for the shape of s −s. Expanding the moments of the PDFs in terms of the pseudoscalar kaon mass, we compute the leading nonanalytic behavior of the number and momentum integrals of the s ands distributions, consistent with the chiral symmetry of QCD. We discuss the implications of our results for the understanding of the NuTeV anomaly and for the phenomenology of strange quark PDFs in global QCD analysis.

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Section: Introductionmentioning

confidence: 99%

Strange-quark asymmetry in the proton in chiral effective theory

Wang

Melnitchouk

et al. 2016

Phys. Rev. D

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“…The rich, low-energy aspects of topics iii) and iv), which may be confronted only with nonperturbative approaches, will also remain uncovered. A comprehensive overview on these subjects and on related topics can be found in several review papers, addressing both their theoretical and experimental aspects [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. Here we will focus on the high-energy regime and the treatment in the context of pQCD approaches of transverse SSA's and, marginally, of the transverse polarization of spin 1/2 particles in unpolarized processes.…”

Section: Introductionmentioning

confidence: 99%

Azimuthal and single spin asymmetries in hard scattering processes

D’Alesio

Murgia

2008

Progress in Particle and Nuclear Physics

183

100

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In this article we review the present understanding of azimuthal and single spin asymmetries for inclusive and semi-inclusive particle production in unpolarized and polarized hadronic collisions at high energy and moderately large transverse momentum. After summarizing the experimental information available, we discuss and compare the main theoretical approaches formulated in the framework of perturbative QCD. We then present in some detail a generalization of the parton model with inclusion of spin and intrinsic transverse momentum effects. In this context, we extensively discuss the phenomenology of azimuthal and single spin asymmetries for several processes in different kinematical configurations. A comparison with the predictions of other approaches, when available, is also given. We finally emphasize some relevant open points and challenges for future theoretical and experimental investigation.

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“…The challenge to understand the spin structure of the proton [1][2][3][4][5][6] has inspired a vast program of theoretical activity and new experiments. Why is the quark spin content g (0)…”

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confidence: 99%

“…How is the spin 1 2 of the proton built up from the spin and orbital angular momentum of the quarks and gluons inside?…”

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confidence: 99%

“…It corresponds to the QCD axial anomaly in the flavor-singlet axial-vector current. C ∞ denotes a potential nonperturbative gluon topological contribution [1] associated with the possible subtraction constant in the dispersion relation for g 1 and possible spin contributions at Bjorken x = 0, that is outside the range of polarzed deep inelastic scattering experiments. The measured singlet axial charge is g (0)…”

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confidence: 99%

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