Photoproduction of positive pions from polarized protons

Dutz, H.; Krämer, D.; Zucht, B.; Althoff, K.H.; Anton, G.; Arends, J.; Beulertz, W.; Böck, Andreas; Breuer, M.; Gehring, R.; Gemander, M.; Goertz, Stefan; Helbing, K.; Hey, J. D.; Meyer, W.; Nöldeke, Georg; Paulsen, R.; Reicherz, G.; Thomas, A.; Wartenberg, S.A.

doi:10.1016/0375-9474(96)00008-5

Cited by 23 publications

(10 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a test, this parameter was fixed and the remaining multipoles varied. The result (Fit 2) is consistent Post-1990 data [7,8] (solid), pre-1990 data [6] (open) symbols.…”

Section: Introductionsupporting

confidence: 74%

See 1 more Smart Citation

Single-energy amplitudes for pion photoproduction in the first resonance region

Workman

2011

Phys. Rev. C

View full text Add to dashboard Cite

We consider multipole amplitudes for low-energy pion photoproduction, constructed with minimal model dependence, at single energies. A previous fit making minimal use of Watson's theorem has been reexamined in light of more recent measurements. Problems associated with the choice of a unique solution are discussed. Comparisons with more recent fits to the full resonance region are made. Explanations are suggested for the discrepancies and more precise measurements of the recoil polarization, P , are motivated.

show abstract

“…As a test, this parameter was fixed and the remaining multipoles varied. The result (Fit 2) is consistent Post-1990 data [7,8] (solid), pre-1990 data [6] (open) symbols.…”

Section: Introductionsupporting

confidence: 74%

“…[1], data from 280 MeV to 420 MeV were fitted using the above prescription and a more recent database [6][7][8]. The higher-multipoles were taken from the MAID analysis [9], which includes vector-meson exchange, rather than a simple electric Born term.…”

Section: Introductionmentioning

confidence: 99%

Single-energy amplitudes for pion photoproduction in the first resonance region

Workman

2011

Phys. Rev. C

View full text Add to dashboard Cite

show abstract

“…A consistent description was achieved by adding a systematic error which increases linearly from 1% at W = 1400 MeV and to 9% at W = 2450 MeV. The beam asymmetry Σ was determined in [55,[88][89][90][91][92][93][94][95][96][97][98], the target asymmetry T in [93,94,[99][100][101][102][103][104][105][106][107][108][109], the neutron recoil polarization can be found in [93,94,110]. A few data from double polarization are available: on G [71,111,112], H [111][112][113], and on the helicity difference σ 3/2 − σ 1/2 [43,86].…”

Section: The Reaction γP → π + Nmentioning

confidence: 99%

Photoproduction of pions and properties of baryon resonances from a Bonn-Gatchina partial-wave analysis

et al. 2010

View full text Add to dashboard Cite

Abstract. Masses, widths and photocouplings of baryon resonances are determined in a coupled-channel partial wave analysis of a large variety of data. The Bonn-Gatchina partial wave formalism is extended to include a decomposition of t-and u-exchange amplitudes into individual partial waves. The multipole transition amplitudes for γp → pπ 0 and γp → nπ + are given and compared to results from other analyses.

show abstract

“…Mostly unpolarized data have been taken but also single polarization observables (e.g. [121]). Hence, the main multipoles are well determined.…”

Section: First Resonance: ∆(1232)mentioning

confidence: 99%

The Gerasimov–Drell–Hearn sum rule

Helbing

2006

Progress in Particle and Nuclear Physics

View full text Add to dashboard Cite

∞ 0 dν ν σ 3/2 (ν) − σ 1/2 (ν) = 2π 2 α m 2 κ 2 (1)Abstract Sum rules measurements involving the spin structure of the nucleon like those due to Bjorken, Ellis and Jaffe and the one due to Gerasimov, Drell and Hearn allow to study the structure of strong interactions. At long distance scales in the confinement regime the Gerasimov-Drell-Hearn (GDH) Sum Rule (Eq. (1)) connects static properties of the nucleon -like the anomalous magnetic moment and the nucleon mass -with the difference of spin dependent doubly polarized total absorption cross sections of real photons. Hence, the full spin-dependent excitation spectrum of the nucleon is being related to its static properties. The sum rule has not been investigated experimentally until recently. Now, for the first time this fundamental sum rule is verified by the GDH-Collaboration with circularly polarized real photons and longitudinally polarized nucleons at the two accelerators Elsa and Mami. The investigation of the response of the proton as well as of the neutron allows to perform an isospin decomposition. Further investigations with real photons are scheduled at Slac, JLab, Spring-8, Legs and Graal. The integral (sum) of the GDH Sum Rule can be generalized to the case of virtual photons. This allows to establish a Q 2 dependency and to study the transition to the perturbative regime of QCD. Ultimately, the GDH Sum Rule can be related to the Bjorken and the Ellis-Jaffe Sum Rule. This transition is the subject of several experiments e.g. at JLab for the resonance region and of the Hermes experiment at Desy for higher Q 2 .This contribution covers the status of theory concerning the GDH Sum Rule as well as the experimental approaches and their results for the absorption of real and virtual photons. We point out that the so-called No-Subtraction hypothesis, often considered the weakest part of the derivation of the GDH Sum Rule, in fact follows from unitarity and does not impair the fundamental character of the GDH Sum Rule. The experimental data verify the GDH Sum Rule for the proton at the level of 8 % including the systematic uncertainties from extrapolations to unmeasured energy regions. For the GDH Sum Rule on the neutron and the isovector case we find unexpected contributions at photon energies above 1 GeV.

show abstract

Photoproduction of positive pions from polarized protons

Cited by 23 publications

References 9 publications

Single-energy amplitudes for pion photoproduction in the first resonance region

Single-energy amplitudes for pion photoproduction in the first resonance region

Photoproduction of pions and properties of baryon resonances from a Bonn-Gatchina partial-wave analysis

The Gerasimov–Drell–Hearn sum rule

Contact Info

Product

Resources

About