Compton scattering from the proton in an effective field theory with explicit Delta degrees of freedom

McGovern, Judith A.; Phillips, Daniel R.; Grießhammer, Harald W.

doi:10.48550/arxiv.1210.4104

Cited by 23 publications

(106 citation statements)

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“…Ongoing work includes embedding the O(e 2 δ 4 ) single-nucleon amplitudes of Ref. [29] for an extension to photon energies above the pion-production threshold, also with ∆-ful pionexchange currents; inclusion of a chirally consistent NN potential; and a detailed assessment of theoretical uncertainties. In support of ongoing and planned experiments at HIγS, MAX-Lab and MAMI, this effort is pursued in the context of a comprehensive theoretical description of Compton scattering on the proton, deuteron and 3 He in χEFT, valid from zero photon energy well into the ∆ resonance region.…”

Section: Discussionmentioning

confidence: 99%

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Dissecting deuteron Compton scattering I: The observables with polarised initial states

Grießhammer

2013

Eur. Phys. J. A

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A complete set of linearly independent observables in Compton scattering with arbitrarily polarised real photons off an arbitrarily polarised spin-1 target is introduced, for the case that the final-state polarisations are not measured. Adopted from the one widely used e.g. in deuteron photo-dissociation, it consists of 18 terms: the unpolarised cross section, the beam asymmetry, 4 target asymmetries and 12 asymmetries in which both beam and target are polarised. They are expressed by the helicity amplitudes and -where available -related to observables discussed by other authors. As application to deuteron Compton scattering, their dependence on the (isoscalar) scalar and spin dipole polarisabilities of the nucleon is explored in Chiral Effective Field Theory with dynamical ∆(1232) degrees of freedom at order e 2 δ 3 . Some asymmetries are sensitive to only one or two dipole polarisabilities, making them particularly attractive for experimental studies. At a photon energy of 100 MeV, a set of 5 observables is identified from which one may be able to extract the spin polarisabilities of the nucleon. These are experimentally realistic but challenging and mostly involve tensor-polarised deuterons. Relative to Compton scattering from a nucleon, sensitivity to the "mixed" spin polarisabilities γ E1M 2 and γ M 1E2 is increased because of interference with the D wave component of the deuteron and with its pion-exchange current. An interactive Mathematica 9.0 notebook with results for all observables at photon energies up to 120 MeV is available from hgrie@gwu.edu.Note May This arXiv version presents the article corrected for these errors.

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Section: Discussionmentioning

confidence: 99%

“…Having established a consistent database from all available proton and deuteron data below 350 MeV in Ref. [1], the static scalar polarisabilities of the proton were recently extracted in this framework with a χ 2 per degree of freedom of 113/135 [29]:…”

Section: Introductionmentioning

confidence: 99%

Dissecting deuteron Compton scattering I: The observables with polarised initial states

Grießhammer

2013

Eur. Phys. J. A

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“…Thus, it is included as an explicit degree of freedom with non-zero width, following Ref. [11]. Here, the ∆(1232) propagates close to its mass shell.…”

Section: Neutron Quasi-free Peakmentioning

confidence: 99%

“…), with the ∆(1232) resonance included as dynamic degrees of freedom [11]. By fitting the theory to the wealth of proton data from Compton scattering experiments on a hydrogen target, the following values for the proton polarizabilities are extracted (in the canonical units of 10 −4 fm 3 ) [11]:…”

Section: Introductionmentioning

confidence: 99%

Extracting neutron polarizabilities from Compton scattering on quasi-free neutron in $\gamma d \to \gamma n p$

Demissie¹,

Grieshammer²

2016

Proceedings of the 8th International Workshop on Chiral Dynamics — PoS(CD15)

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Compton scattering processes are ideal to study electric and magnetic dipole polarizabilities of nucleons. These fundamental quantities parametrize the responses of the internal degrees of freedoms to a monochromatic photon probe. In this work, the inelastic channel γd → γnp is treated in χEFT, with a focus on the kinematic region of the neutron quasi-free peak, where the momentum of the outgoing proton is small enough that it is considered to remain at rest. This provides access to the Compton scattering process γn → γn, from which the scalar polarizabilites of the neutron, α E1 and β M1 , are extracted. Using χEFT, triple differential cross-sections d 3 σ /dE n dΩ γ ′ Ω n in the photon energy range of 200-to-400 MeV are computed. The biggest contribution comes from the impulse approximation, with small corrections stemming from final state interactions, meson exchange currents and rescattering. In this presentation, we report progress and preliminary results.

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“…In principle, this is easiest for the proton, however, the low-energy limit is dominated by the total charge interaction, the Thomson cross section; and, while increasing the energy leads to increased sensitivity to polarizabilities, it also introduces higher-order response of the nucleon. For the most recent comprehensive analysis of proton Compton scattering, see [3].…”

Section: Electromagnetic Polarizabilitiesmentioning

confidence: 99%

Lattice QCD Methods for Hadronic Polarizabilities

Tiburzi¹

2013

Proceedings of the 7th International Workshop on Chiral Dynamics — PoS(CD12)

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Chiral dynamics makes definitive predictions for the electromagnetic polarizabilities of hadrons near the chiral limit; but, agreement with experiment is tenuous in some cases. We provide an overview of lattice QCD methods to compute the electric and magnetic polarizabilities of hadrons. Central to these methods is the lattice simulation of quarks in uniform, classical electromagnetic fields. A long-term goal is the determination of polarizabilities directly from lattice computations, however, in the near term, one may need to rely on partially quenched chiral perturbation theory. Nonetheless the same striking predictions for the pion mass dependence of electric and magnetic polarizabilities can be made from chiral dynamics, and tested with lattice QCD. A particular focus is a novel new method to handle charged particle correlation functions in magnetic fields.

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Compton scattering from the proton in an effective field theory with explicit Delta degrees of freedom

Cited by 23 publications

References 0 publications

Dissecting deuteron Compton scattering I: The observables with polarised initial states

Dissecting deuteron Compton scattering I: The observables with polarised initial states

Extracting neutron polarizabilities from Compton scattering on quasi-free neutron in $\gamma d \to \gamma n p$

Lattice QCD Methods for Hadronic Polarizabilities

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