Chiral Extrapolation of Lattice Moments of Proton Quark Distributions

Detmold, William; Melnitchouk, Wally; Negele, John W.; Renner, Dru B.; Thomas, A. W.

doi:10.1103/physrevlett.87.172001

Cited by 159 publications

(194 citation statements)

References 35 publications

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“…Any effective theory or model of QCD must therefore reproduce exactly these coefficients, the most notable of which are the leading nonanalytic (LNA) terms, if it is consistent with the symmetries of QCD. For moments of PDFs, the LNA terms were found previously [36][37][38] to have a characteristic m 2 π log m 2 π dependence (for pion loops), a feature which was applied [39] to analyze the chiral behavior of lattice moments of the isovector quark PDFs.…”

Section: B Leading Nonanalytic Behaviormentioning

confidence: 99%

“…Starting from the most general effective Lagrangian consistent with the chiral symmetry of QCD, at a given order in the chiral expansion a unique set of diagrams can be identified and computed systematically [37][38][39]. The long distance (m K → 0) effects in such expansions are thus dictated solely by chiral symmetry and gauge invariance, while the short distance contributions are treated with a particular regularization procedure.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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: B Leading Nonanalytic Behaviormentioning

confidence: 99%

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 proposal to resolve this discrepancy in [20] introduces a cut-off by hand into the leading order chiral perturbation theory expansion of x which effectively limits the size of the pion cloud. For this proposal to have predictive power it is required that this cut-off parameter is independent of the observable under consideration.…”

Section: The Moment X U-dmentioning

confidence: 99%

Parton distributions from the lattice

Schroers¹

2005

Nuclear Physics A

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I review the current status of lattice calculations for two selected observables related to nucleon structure: the second moment of the unpolarized parton distribution, (u-d), and the first moment of the polarized parton distribution, the non-singlet axial coupling gA. The major challenge is the requirement to extract them sufficiently close to the chiral limit. In the former case, there still remains a puzzling disagreement between lattice data and experiment. For the latter quantity, however, we may be close to obtaining its value from the lattice in the immediate future.Comment: Invited review at BARYONS 2004, Palaiseau, France, October 25 - 29, 200

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“…(30) governing the leading-non-analytic quarkmass behaviour of this moment is not responsible for the rising behaviour of the chiral extrapolation function, as had been hypothesized in ref. [35]. It will be interesting to see how well our O(p 2 ) BChPT extrapolation formula for x u−d will perform, once the new lattice QCD data from dynamical simulations at small quark masses for moments of GPDs become available [39].…”

Section: Moments Of the Isovector Gpds At T =mentioning

confidence: 99%

Chiral perturbation theory and the first moments of the generalized parton distributions in a nucleon

2008

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We discuss the first moments of the parity-even Generalized Parton Distributions (GPDs) in a nucleon, corresponding to six (generalized) vector form factors. We evaluate these fundamental properties of baryon structure at low energies, utilizing the methods of covariant Chiral Perturbation Theory in the baryon sector (BChPT). Our analysis is performed at leading-one-loop order in BChPT, predicting both the momentum and the quark-mass dependence for the three (generalized) isovector and (generalized) isoscalar form factors, which are currently under investigation in lattice QCD analyses of baryon structure. We also study the limit of vanishing four-momentum transfer where the GPD-moments reduce to the well known moments of Parton Distribution Functions (PDFs). For the isovector moment x u−d our BChPT calculation predicts a new mechanism for chiral curvature, connecting the high values for this moment typically found in lattice QCD studies for large quark masses with the smaller value known from phenomenology. Likewise, we analyze the quark-mass dependence of the isoscalar moments in the forward limit and extract the contribution of quarks to the total spin of the nucleon. We close with a first glance at the momentum dependence of the isoscalar C-form factor of the nucleon.

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Chiral Extrapolation of Lattice Moments of Proton Quark Distributions

Cited by 159 publications

References 35 publications

Strange-quark asymmetry in the proton in chiral effective theory

Strange-quark asymmetry in the proton in chiral effective theory

Parton distributions from the lattice

Chiral perturbation theory and the first moments of the generalized parton distributions in a nucleon

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