Helicity Dependence of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">γ</mml:mi><mml:mi mathvariant="italic">p</mml:mi><mml:mspace /><mml:mo>→</mml:mo><mml:mspace /><mml:mi mathvariant="italic">N</mml:mi><mml:mi mathvariant="italic">π</mml:mi></mml:math>below 450 MeV and Contribution to the Gerasimov-Drell-Hearn Sum Rule

Ahrens, J.; Altieri, S.; Annand, J. R. M.; Anton, G.; Arends, H. J.; Aulenbacher, K.; Beck, R.; Bradtke, C.; Braghieri, A.; Degrande, N.; d’Hose, N.; Dutz, H.; Goertz, Stefan; Grabmayr, P.; Hansen, Kurt Schaldemose; Harmsen, J.; Harrach, D. von; Hasegawa, S.; Hasegawa, T.; Heid, E.; Helbing, K.; Holvoet, H.; Hoorebeke, Luc Van; Horikawa, N.; Iwata, T.; Jennewein, P.; Kageya, T.; Kiel, B.; Клейн, Ф.; Kondratiev, R.; Kossert, Karsten; Krimmer, J.; Lang, Μ.; Lannoy, B.; Leukel, R.; Lisin, V.; Matsuda, T.; McGeorge, J. C.; Meier, A.; Menze, D.; Meyer, W.; Michel, Thilo; Naumann, J.; Owens, R.O.; Panzeri, A.; Pedroni, P.; Pinelli, T.; Preobrajenski, I.; Radtke, Edgar; Reichert, E.; Reicherz, G.; Rohlof, Ch.; Ryckbosch, D.; Sadiq, F; Sauer, Michelle; Schoch, B.; Schumacher, M.; Seitz, B.; Speckner, T.; Steigerwald, Michael L.; Takabayashi, N.; Tamas, G.; Thomas, A.; Vyver, R. Van de; Wakai, A.; Weihofen, W.; Wissmann, F.; Zapadtka, F.; Zeitler, G.

doi:10.1103/physrevlett.84.5950

Cited by 95 publications

(60 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the weighting factor ν −3 , the threshold region below 200 MeV contributes substantially, while the region above 800 MeV is of little importance. In the case of γ 0 , the integrand in the resonance region (200 MeV< ν <800 MeV) has now been measured at MAMI [11]. The experimental value is (-1.71±0.09) 10 −4 fm 4 , slightly smaller than the prediction of MAID, -1.66·10 −4 fm 4 .…”

Section: Resultsmentioning

confidence: 84%

“…Our present analysis is shown in Table I. In the region 200 MeV< ν <800 MeV we can now rely on the experimental data taken in 1998 at MAMI [11]. We are quite confident about our estimate for the integrand between threshold and 200 MeV, because here the cross sections are largely determined by s-wave pion production via the amplitude E 0+ fixed through low energy theorems.…”

Section: Resultsmentioning

confidence: 95%

“…The range of momentum transfer below these values will be covered by various experiments at the Jefferson Lab, which are being performed in the full range 0.02(GeV /c) 2 ≤ Q 2 ≤ 2 (GeV/c) 2 [10]. The first direct experimental data for real photons (Q 2 = 0) were recently taken at MAMI [11] in the energy range 200 MeV< ν < 800 MeV, and data at the higher energies are expected from ELSA within short.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Gerasimov-Drell-Hearn sum rule and related integrals

2001

View full text Add to dashboard Cite

The spin structure of the nucleon resonance region is analyzed on the basis of our phenomenological model MAID. Predictions are given for the Gerasimov-Drell-Hearn sum rule as well as generalized integrals over spin structure functions. The dependence of these integrals on momentum transfer is studied and rigorous relationships between various definitions of generalized Gerasimov-Drell-Hearn integrals and spin polarizabilities are derived. These results are compared to the predictions of chiral perturbation theory and phenomenological models.

show abstract

Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Gerasimov-Drell-Hearn sum rule and related integrals

2001

View full text Add to dashboard Cite

show abstract

“…The contribution of single π 0 production to the GDH integral is evaluated. The total GDH integral up to 2.9 GeV was determined to I 2.9 tot = 226 ± 5 stat ± 12 syst µb [23][24][25][26][27]; the results were summarized in [3]. Here, a contribution of 27.5 µb had been subtracted to account for the description of the very low energy region by MAID [8].…”

Section: Pacs Numbersmentioning

confidence: 99%

First Measurement of the Helicity Asymmetry forγp→pπ0in the Resonance Region

Gottschall¹,

Anisovich²,

Bantes³

et al. 2014

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300 MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed which are traced to differences in the helicity amplitudes of well known and established resonances. Precise values for the helicity amplitudes of several resonances are reported. PACS numbers:The spin structure of the proton has been of topical interest since the discovery that the quark spins constitute an unexpectedly small fraction of the proton spin [1]. Deep inelastic scattering experiments have revealed gluonic contributions to the proton spin to be consistent with zero, at least within the admittedly large errors [2]. At low energies, a different aspect of the proton spin structure is tested by a comparison of the helicity dependence of the total γp cross section integrated over all photon energies, ∞ 0 dE γ (σ 3/2 − σ 1/2 )/E γ , with the proton magnetic moment [3], a relation which is known as Gerasimov-Drell-Hearn (GDH) sum rule [4,5]. The subscripts denote the total helicity, h = 1/2 for photon and proton spin anti-aligned, h = 3/2 for both spins aligned. The GDH integral sums over all energies and all final states. A breakdown of the GDH integral into exclusive final states can provide a link between inclusive properties of the proton like its magnetic moment and the contributions of specific nucleon resonances to the GDH integral.In this letter, we report the first measurement of the double polarization observable(1) for the exclusive reaction γp → pπ 0 in the energy range from 600 to 2300 MeV, and compare the results with predictions of well established partial wave analyses (PWA) like SAID [6,7], MAID [8], and BnGa [9]. The double polarization observable G [10] -governing the correlation between linearly polarized photons and longitudinally polarized target protons -revealed remarkable differences in the predictions of the three partial wave analysis groups even in the well-studied 2 nd resonance region around E γ =750 MeV [11]. Here, we extend the covered energy regime to 2.3 GeV for the double polarization observable E. So far, data on E were published up to 780 MeV for a limited angular range [12,13]; further data from CLAS exist and were reported at a conference [14].The experiment was carried out using the tagged photon beam of the ELectron Stretcher Accelerator ELSA at Bonn [15]. Photons with circular polarization [16],were produced by scattering a 2.4 GeV beam of longitudinally polarized electrons with polarization P e − off a bremsstrahlung target. The electrons were deflected by a magnet into a tagging hodoscope which defines the energy of the bremsstrahlung photons. The electron polarization (P e − ≈ 0.60) was monitored in a Møller polarimeter [17]. The photon beam impinged on a butanol (C 4 H 9 OH) target, which was p...

show abstract

“…[7] with experimental data from refs. [9][10][11]. Around the ∆-resonance mass, the model overestimates the experimental cross sections by about 10%.…”

Section: Jhep01(2014)077mentioning

confidence: 99%

Beam-helicity asymmetry in associated electroproduction of real photons ep → eγπN in the Δ-resonance region

Airapetian¹,

Акопов²,

Aschenauer³

et al. 2014

J. High Energ. Phys.

Self Cite

View full text Add to dashboard Cite

Abstract:The beam-helicity asymmetry in associated electroproduction of real photons, ep → eγπN , in the ∆(1232)-resonance region is measured using the longitudinally polarized Hera positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, ep → eγπ 0 p and ep → eγπ + n, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.

show abstract

Helicity Dependence ofγp→Nπbelow 450 MeV and Contribution to the Gerasimov-Drell-Hearn Sum Rule

Cited by 95 publications

References 18 publications

Gerasimov-Drell-Hearn sum rule and related integrals

Gerasimov-Drell-Hearn sum rule and related integrals

First Measurement of the Helicity Asymmetry forγp→pπ0in the Resonance Region

Beam-helicity asymmetry in associated electroproduction of real photons ep → eγπN in the Δ-resonance region

Contact Info

Product

Resources

About