Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities

Martel, P. P.; Miskimen, R.; Aguar-Bartolomé, P.; Ahrens, J.; Akondi, C. S.; Annand, J. R. M.; Arends, H. J.; Barnes, William S.; Beck, R.; Bernstein, A. M.; Borisov, N. S.; Braghieri, A.; Briscoe, W. J.; Cherepnya, S.; Collicott, C.; Costanza, S.; Denig, A.; Dieterle, M.; Downie, E. J.; Filʼkov, L.V.; Garni, S.; Glazier, D. I.; Gradl, W.; Gurevich, G. M.; Barrientos, Pauline Hall; Hamilton, D.; Hornidge, D.; Howdle, D.; Huber, G. M.; Jude, T. C.; Kaeser, Adam J.; Kashevarov, V. L.; Keshelashvili, I.; Kondratiev, R.; Korolija, M.; Krusche, B.; Lazarev, A. B.; Lisin, V.; Livingston, K.; MacGregor, I. J. D.; Mancell, J.; Manley, D. M.; Meyer, W.; Middleton, D. G.; Mushkarenkov, A.; Nefkens, B. M. K.; Neganov, A. B.; Nikolaev, A.; Oberle, M.; Spina, H. Ortega; Ostrick, M.; Ott, P. S.; Otte, P. B.; Oussena, B.; Pedroni, P.; Polonski, A.; Polyansky, V. V.; Prakhov, S.; Rajabi, A. A.; Reicherz, G.; Rostomyan, T.; Sarty, A. J.; Schrauf, S.; Schumann, S.; Sikora, M. H.; Starostin, A.; Steffen, O.; Strakovsky, I. I.; Strub, Th.; Supek, I.; Thiel, M.; Tiator, L.; Thomas, A.; Unverzagt, M.; Usov, Yu. A.; Watts, D. P.; Witthauer, L.; Werthmüller, D.; Wolfes, M.

doi:10.1103/physrevlett.114.112501

Cited by 42 publications

(53 citation statements)

References 30 publications

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“…Finally we quote the results from a recent fit within subtracted DRs (61), which uses as input the MAID07 pion-photoproduction multipoles (45), and the values for the spin polarizabilities extracted from double polarization RCS measurements at MAMI (64). These results clearly show that the tension for βM1 between the fits within effective field theories and DRs persists.…”

Section: Static Polarizabilitiesmentioning

confidence: 88%

Dispersion Theory in Electromagnetic Interactions

Pasquini

Vanderhaeghen

2018

Annu. Rev. Nucl. Part. Sci.

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We review various applications of dispersion relations (DRs) to the electromagnetic structure of hadrons. We discuss the way DRs allow one to extract information on hadron structure constants by connecting information from complementary scattering processes. We consider the real and virtual Compton scattering processes off the proton, and summarize recent advances in the DR analysis of experimental data to extract the proton polarizabilities, in comparison with alternative studies based on chiral effective field theories. We discuss a multipole analysis of real Compton scattering data, along with a DR fit of the energy-dependent dynamical polarizabilities. Furthermore, we review new sum rules for the double-virtual Compton scattering process off the proton, which allow for model independent relations between polarizabilities in real and virtual Compton scattering, and moments of nucleon structure functions. The information on the double-virtual Compton scattering is used to predict and constrain the polarizability corrections to muonic hydrogen spectroscopy.

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Section: Static Polarizabilitiesmentioning

confidence: 88%

Dispersion Theory in Electromagnetic Interactions

Pasquini

Vanderhaeghen

2018

Annu. Rev. Nucl. Part. Sci.

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“…We then have restricted ourselves to fit the sets {α E1 , β M 1 } or {α E1 , β M 1 , γ π }, which mainly affect the unpolarized RCS cross section below pion-production threshold. The remaining spin polarizabilities have been fixed to the available experimental information [3,[31][32][33]. Furthermore, we consider different fit conditions, switching on/off the systematic errors and with/without the constraint of the Baldin's sum rule for the polarizability sum α E1 + β M 1 .…”

Section: Discussionmentioning

confidence: 99%

“…(20) for the scalar dipole polarizabilities and the experimental values of Ref. [31] for the leading-order spin polarizabilities are shown in Fig. 11 as a function of the lab photon energy E γ and the lab scattering angle θ lab , in comparison with the experimental data of the FULL data set.…”

Section: Available Extractions Of Rcs Scalar Dipole Static Polarimentioning

confidence: 97%

Proton scalar dipole polarizabilities from real Compton scattering data using fixed-t subtracted dispersion relations and the bootstrap method

Pasquini¹,

Pedroni²,

Sconfietti³

2019

J. Phys. G: Nucl. Part. Phys.

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We perform a fit of the real Compton scattering (RCS) data below pion-production threshold to extract the electric (αE1) and magnetic (βM1) static scalar dipole polarizabilities of the proton, using fixed-t subtracted dispersion relations and a bootstrap-based fitting technique. The bootstrap method provides a convenient tool to include the effects of the systematic errors on the best values of αE1 and βM1 and to propagate the statistical errors of the model parameters fixed by other measurements. We also implement various statistical tests to investigate the consistency of the available RCS data sets below pion-production threshold and we conclude that there are not strong motivations to exclude any data point from the global set. Our analysis yields αE1 = (12.03 +0.48 −0.54 ) × 10 −4 fm 3 and βM1 = (1.77 +0.52 −0.54 ) × 10 −4 fm 3 , with p-value = 12%. I. INTRODUCTIONThe electric and magnetic static scalar dipole polarizabilities, α E1 and β M 1 , respectively, are fundamental structure constants of the proton that can be accessed via real Compton scattering (RCS). In the low-energy expansion of the Compton amplitude, they correspond to the leading-order contributions beyond the structure independent terms that describe the scattering process as if the proton were a pointlike particle with anomalous magnetic moment. When approaching the pion-production threshold, also higher-order terms start competing with the scalar dipole polarizabilities. Therefore, one has to resort to reliable theoretical frameworks for extracting the scalar dipole polarizabilities from experimental data. The most accredited theories, which have been used sofar, are fixed-t dispersion relations (DRs), in the unsubtracted [1-3] and subtracted [4][5][6][7][8] formalism, and chiral perturbation theory (χPT) with explicit nucleons and Delta's, in the variant of heavy-baryon χPT (HBχPT) [9-11] and manifestly covariant [12,13] χPT (BχPT) 1 . Based on these theoretical frameworks, extractions of the scalar dipole polarizabilities have been obtained by fitting different data sets for the unpolarized RCS cross section, and adopting a statistical approach based on the conventional χ 2 -minimization procedure. Recently, a new statistical method has successfully been applied in Ref. [16] to analyze RCS data at low energies and extract values for the energy-dependent scalar dipole dynamical polarizabilities [17,18]. The method is based on the parametric-bootstrap technique, and it is adopted in this work to extract the scalar dipole static polarizabilities, using the updated version of fixed-t subtracted DRs formalism [8] as theoretical framework. Although the bootstrap method is rarely used in nuclear physics [16,[19][20][21][22], it has high potential and advantages [23]. In particular, we will show that it allows us to include the systematic errors in the data analysis in a straightforward way and to efficiently reconstruct the probability distributions of the fitted parameters. We will also pay a special attention to discuss the available sets of ...

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“…Fig. 17 contrasts experimental results from A2/MAMI [125] with predictions from dispersion theory and chiral perturbation theory. Instead of the spin polar- 2-body kernels same as for mesons, no further approximations: We compare to experiment [125], dispersion theory [1,128,129], leading-order ChPT [53], and higher-order chiral approaches [130][131][132][133][134][135]; see Refs.…”

Section: Compton Form Factorsmentioning

confidence: 97%

“…Resonance contributions to the nucleon's scalar and spin polarizabilities. The experimental values of α and β are from the PDG[81] and those for the spin polarizabilities from Refs [125][126][127]…”

mentioning

confidence: 99%

Nucleon resonances in Compton scattering

Eichmann

Ramalho

2018

Phys. Rev. D

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We calculate the nucleon resonance contributions to nucleon Compton scattering, including all states with J P = 1/2 ± and J P = 3/2 ± where experimental data for their electromagnetic transition form factors exist. To this end, we construct a tensor basis for the Compton scattering amplitude based on electromagnetic gauge invariance, crossing symmetry and analyticity. The corresponding Compton form factors provide a Lorentz-invariant description of the process in general kinematics, which reduces to the static and generalized polarizabilities in the appropriate kinematic limits. We derive the general forms of the offshell nucleon-to-resonance transition vertices that implement electromagnetic and spin-3/2 gauge invariance, which automatically also defines onshell transition form factors that are free of kinematic constraints. We provide simple fits for those form factors, which we use to analyze the resulting Compton form factors and extract their contributions to the nucleon's polarizabilities. Apart from the ∆(1232), the resonance contributions to the scalar and spin polarizabilites are very small, although the N (1520) could play a role for the proton's magnetic polarizability.

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Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities

Cited by 42 publications

References 30 publications

Dispersion Theory in Electromagnetic Interactions

Dispersion Theory in Electromagnetic Interactions

Proton scalar dipole polarizabilities from real Compton scattering data using fixed-t subtracted dispersion relations and the bootstrap method

Nucleon resonances in Compton scattering

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