Aspects of nucleon Compton scattering

Bernard, Véronique; Kaiser, Norbert; Meißner, Ulf‐G.; Schmidt, A.

doi:10.1007/bf01305891

Cited by 80 publications

(71 citation statements)

References 27 publications

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“…All of these effects produce a Delta-contribution to the magnetic polarizability that is significantly smaller than that found in previous EFT calculations with explicit Deltas [21][22][23]25]:…”

Section: B Polarizabilitiesmentioning

confidence: 79%

“…First of all, in contrast to the results of Refs. [13,22], they are independent of "off-shell parameters".…”

Section: B Polarizabilitiesmentioning

confidence: 99%

“…Refs. [13,19,[22][23][24]. As a rule, standard couplings do not have the spin-3/2 gauge symmetry (14).…”

Section: The Chiral Lagrangianmentioning

confidence: 99%

“…The predictions made in Refs. [19,21,22] are obscured by off-shell ambiguities, in particular by the so-called "off-shell parameters" which control the infamous spin-1/2 sector of the spin-3/2 Delta field. In a "reasonable" range for these parameters the Delta contribution to β (∆) p varies between 0 and 14 × 10 −4 fm 3 [22].…”

Section: Introductionmentioning

confidence: 99%

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Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

2003

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We formulate a new power-counting scheme for a chiral effective field theory of nucleons, pions, and Deltas. This extends chiral perturbation theory into the Delta-resonance region. We calculate nucleon Compton scattering up to next-to-leading order in this theory. The resultant description of existing γp cross section data is very good for photon energies up to about 300 MeV. We also find reasonable numbers for the spin-independent polarizabilities α p and β p .

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Section: B Polarizabilitiesmentioning

confidence: 79%

“…First of all, in contrast to the results of Refs. [13,22], they are independent of "off-shell parameters".…”

Section: B Polarizabilitiesmentioning

confidence: 99%

“…Refs. [13,19,[22][23][24]. As a rule, standard couplings do not have the spin-3/2 gauge symmetry (14).…”

Section: The Chiral Lagrangianmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

2003

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“…The calculation was later repeated in heavy-baryon ChPT, which allows for a consistent chiral power counting, and extended to O(p 4 ) yielding α p E1 = 10.5 ± 2.0 and β p M1 = 3.5 ± 3.6 (Bernard et al, 1994(Bernard et al, , 1993. The error bars for these values indicate that several low-energy constants appear at this order, which were determined by resonance saturation, that is by use of phenomenological information about resonances and vector mesons.…”

Section: Theoretical Developmentsmentioning

confidence: 99%

Hadron structure at lowQ2

Drechsel

Walcher

2008

Rev. Mod. Phys.

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This review deals with the structure of hadrons, strongly interacting many-body systems consisting of quarks and gluons. These systems have a size of about 1 fm, which shows up in scattering experiments at low momentum transfers Q in the GeV region. At this scale the running coupling constant of Quantum Chromodynamics (QCD), the established theory of the strong interactions, becomes divergent. It is therefore highly intriguing to explore this theory in the realm of its strong interaction regime. However, the quarks and gluons can not be resolved at the GeV scale but have to be studied through their manifestations in the bound many-body systems, for instance pions, nucleons and their resonances. The review starts with a short overview of QCD at low momentum transfer and a summary of the theoretical apparatus describing the interaction of hadrons with electrons and photons. In the following sections we present the experimental results for the most significant observables studied with the electromagnetic probe: form factors, polarizabilities, excitation spectra, and sum rules. These experimental findings are compared and interpreted with various theoretical approaches to QCD, such as phenomenological models with quarks and pions, dispersion relations as a means to connect observables from different experiments, and, directly based on the QCD lagrangian, chiral perturbation theory and lattice gauge theory.

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Chiral Expansion of Baryon Masses andσ-Terms

1997

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We analyze the octet baryon masses and the pionÂkaon-nucleon _-terms in the framework of heavy baryon chiral perturbation theory. We include all terms up-to-and-including quadratic order in the light quark masses, m q . We develop a consistent scheme to estimate low-energy constants related to scalar-isoscalar operators in the framework of resonance exchange involving one-loop graphs. The pertinent low-energy constants can only be estimated up to some finite coefficients. Including contributions from loop graphs with intermediate spin-3Â2 decuplet and spin-1Â2 octet states and from tree graphs including scalar mesons, we use the octet baryon masses and the pion-nucleon _-term to fix all but one of these coefficients. Physical results are insensitive to this remaining parameter. It is also demonstrated that two-loop corrections only modify some of the subleading low-energy constants. We find for the baryon mass in the chiral limit, m # =770\110 MeV. While the corrections of order m 2 q are small for the nucleon, they are still sizeable for the 4, the 7 and the 5. Therefore a definitive statement about the convergence of three-flavor baryon chiral perturbation can not yet be made. The strangeness content of the nucleon is y=0.21\0.20. We also estimate the kaon-nucleon _-terms and some two-loops contributions to the nucleon mass.1997 Academic Press

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Aspects of nucleon Compton scattering

Cited by 80 publications

References 27 publications

Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

Hadron structure at lowQ2

Chiral Expansion of Baryon Masses andσ-Terms

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