On chiral corrections to nucleon GPD

Thomas

2013

3. The right to use all or part of the Article, including the APS-prepared version without revision or modification, on the author(s)' web home page or employer's website and to make copies of all or part of the Article, including the APS-prepared version without revision or modification, for the author(s)' and/or the employer's use for educational or research purposes." February 2014Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling We present a relativistic formulation of pion loop corrections to the coupling of photons with nucleons on the light front. Vertex and wave function renormalization constants are computed to lowest order in the pion field, including their nonanalytic behavior in the chiral limit, and studied numerically as a function of the ultraviolet cutoff. Particular care is taken to explicitly verify gauge invariance and Ward-Takahashi identity constraints to all orders in the m expansion. The results are used to compute the chiral corrections to matrix elements of local operators, related to moments of deep-inelastic structure functions. Finally, comparison of results for pseudovector and pseudoscalar coupling allows the resolution of a longstanding puzzle in the computation of pion cloud corrections to structure function moments.

“…(46) and (47), are true to all orders in the pion mass, not just for the LNA parts that were discussed in Refs. [17,18,48], and to which we turn to in the next section.…”

Section: A Pionic Corrections To Twist-2 Matrix Elementsmentioning

confidence: 96%

Anatomy of relativistic pion loop corrections to the electromagnetic nucleon coupling

Thomas

2013

“…From the transformation properties of the operators O µ 1 ···µn q and O µ 1 ···µn ∆q under parity [25], the sets of coefficients {α (n) , β (n) , σ (n) , θ (n) , ρ (n) } and {ᾱ (n) ,β (n) ,σ (n) ,θ (n) ,ρ (n) } in (15) are the same as those in the spin-averaged operators in (11).…”

Section: A Operators and Momentsmentioning

confidence: 99%

Parton distributions from nonlocal chiral SU(3) effective theory: Flavor asymmetries

Salamu

et al. 2019

Using recently derived results for one-loop hadronic splitting functions from a nonlocal implementation of chiral effective theory, we study the contributions from pseudoscalar meson loops to flavor asymmetries in the proton. Constraining the parameters of the regulating functions by inclusive production of n, ∆ ++ , Λ and Σ * + baryons in pp collisions, we compute the shape of the light antiquark asymmetryd −ū in the proton and the strange asymmetry s −s in the nucleon sea.With these constraints, the magnitude of thed −ū asymmetry is found to be compatible with that extracted from the Fermilab E866 Drell-Yan measurement, with no indication of a sign change at large values of x, and an integrated value in the range d −ū ≈ 0.09 − 0.17. The s −s asymmetry is predicted to be positive at x > 0, with compensating negative contributions at x = 0, and an integrated x-weighted moment in the range x(s −s) ≈ (0.9 − 2.5) × 10 −3 .

“…According to the properties of O µ 1 ···µn q and O µ 1 ···µn ∆q under parity transformations [49], the coefficients {α (n) , β (n) , σ (n) } and {ᾱ (n) ,β (n) ,σ (n) } are the same as for the spin-averaged operators in Eq. (25).…”

Section: Matching Coefficients and Pdf Momentsmentioning

confidence: 99%

Strange-quark asymmetry in the proton in chiral effective theory

Wang

et al. 2016

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.