Nucleon spin-polarisabilities from polarisation observables in low-energy deuteron Compton scattering

Grießhammer, Harald W.; Shukla, Deepshikha

doi:10.1140/epja/i2010-11037-6

Cited by 3 publications

(26 citation statements)

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“…Insofar, this publication extends the so-far most thorough work in Ref. [10], including its Erratum.…”

Section: Introductionsupporting

confidence: 55%

“…Observables by Chen et al [6], Choudhury/Phillips [8,9] and Grießhammer/Shukla [10] These authors define observables in analogy to those introduced by Babusci et al [5]. However, the deuteron is taken to be prepared such that only the magnetic quantum numbers M i d = ±1 contribute, in the direction d in which the density matrix is diagonal.…”

Section: Polarised Deuteronmentioning

confidence: 99%

“…[6,[8][9][10]] is now straightforward. Asymmetries with unpolarised targets are of course identical, Eq.…”

Section: Polarised Deuteronmentioning

confidence: 99%

“…Conflicting results from MAMI and LEGS exist for the proton, and large error-bars are found for the neutron [30]. The isoscalar values are in the range (see also [10]):…”

Section: Introductionmentioning

confidence: 99%

“…However, a corresponding list of 23 independent observables (12 complex amplitudes minus an overall phase) is missing. While several single and double polarisation observables have been constructed and their sensitivity to the nucleon polarisabilities explored [6][7][8][9][10], no systematic study of vector and tensor polarisation observables exists. Only one tensor observable has been considered explicitly, namely for an unpolarised beam [11][12][13].…”

Section: Introductionmentioning

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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“…Insofar, this publication extends the so-far most thorough work in Ref. [10], including its Erratum.…”

Section: Introductionsupporting

confidence: 55%

Section: Polarised Deuteronmentioning

confidence: 99%

“…[6,[8][9][10]] is now straightforward. Asymmetries with unpolarised targets are of course identical, Eq.…”

Section: Polarised Deuteronmentioning

confidence: 99%

“…Conflicting results from MAMI and LEGS exist for the proton, and large error-bars are found for the neutron [30]. The isoscalar values are in the range (see also [10]):…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Grießhammer

2013

Eur. Phys. J. A

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Using Effective Field Theory to analyse low-energy Compton scattering data from protons and light nuclei

Grießhammer

McGovern

Phillips

et al. 2012

Progress in Particle and Nuclear Physics

168

353

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Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. For photon energies up to about 300 MeV, the process can be parameterised by six dynamical dipole polarisabilities which characterise the response of the nucleon to a monochromatic photon of fixed frequency and multipolarity. Their zero-energy limit yields the well-known static electric and magnetic dipole polarisabilities α E1 and β M 1 , and the four dipole spin polarisabilities. The emergence of full lattice QCD results and new experiments at MAMI (Mainz), HIγS at TUNL, and MAX-Lab (Lund) makes this an opportune time to review nucleon Compton scattering. Chiral Effective Field Theory (χEFT) provides an ideal analysis tool, since it encodes the well-established low-energy dynamics of QCD while maintaining an appropriately flexible form for the Compton amplitudes of the nucleon. The same χEFT also describes deuteron and 3 He Compton scattering, using consistent nuclear currents, rescattering and wave functions, and respects the low-energy theorems for photon-nucleus scattering. It can thus also be used to extract useful information on the neutron amplitude from Compton scattering on light nuclei. We summarise past work in χEFT on all of these reactions and compare with other theoretical approaches. We also discuss all proton experiments up to about 400 MeV, as well as the three modern elastic deuteron data sets, paying particular attention to the precision and accuracy of each set. Constraining the ∆(1232) parameters from the resonance region, we then perform new fits to the proton data up to ω lab = 170 MeV, and a new fit to the deuteron data. After checking in each case that a two-parameter fit is compatible with the respective Baldin sum rules, we obtain, using the sum-rule constraints in a one-parameter fit, α (p) E1 = 10.7 ± 0.3(stat) ± 0.2(Baldin) ± 0.8(theory), β (p) M 1 = 3.1 ∓ 0.3(stat) ± 0.2(Baldin) ± 0.8(theory), for the proton polarisabilities, and α (s) E1 = 10.9 ± 0.9(stat) ± 0.2(Baldin) ± 0.8(theory), β (s)M 1 = 3.6 ∓ 0.9(stat) ± 0.2(Baldin) ± 0.8(theory), for the isoscalar polarisabilities, each in units of 10 −4 fm 3 . Finally, we discuss plans for polarised Compton scattering on the proton, deuteron, 3 He and heavier targets, their promise as tools to access spin polarisabilities, and other future avenues for theoretical and experimental investigation.

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Elastic Compton scattering from 3He and the role of the Delta

et al. 2018

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We report observables for elastic Compton scattering from 3 He in Chiral Effective Field Theory with an explicit ∆(1232) degree of freedom (χEFT) for energies between 50 and 120 MeV. The γ 3 He amplitude is complete at N 3 LO, O(e 2 δ 3 ), and in general converges well order by order. It includes the dominant pion-loop and two-body currents, as well as the Delta excitation in the single-nucleon amplitude. Since the cross section is two to three times that for deuterium and the spin of polarised 3 He is predominantly carried by its constituent neutron, elastic Compton scattering promises information on both the scalar and spin polarisabilities of the neutron. We study in detail the sensitivities of 4 observables to the neutron polarisabilities: the cross section, the beam asymmetry and two double asymmetries resulting from circularly polarised photons and a longitudinally or transversely polarised target. Including the Delta enhances those asymmetries from which neutron spin polarisabilities could be extracted. We also correct previous, erroneous results at N 2 LO, i.e. without an explicit Delta, and compare to the same observables on proton, neutron and deuterium targets. An interactive Mathematica notebook of our results is available from hgrie@gwu.edu. 2S J=0 √ 2J + 1 P S J J M =−J

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Nucleon spin-polarisabilities from polarisation observables in low-energy deuteron Compton scattering

Cited by 3 publications

References 50 publications

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

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

Using Effective Field Theory to analyse low-energy Compton scattering data from protons and light nuclei

Elastic Compton scattering from 3He and the role of the Delta

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