Updated SAID analysis of pion photoproduction data

Workman, R. L.; Briscoe, W. J.; Paris, Mark W.; Strakovsky, I. I.

doi:10.1103/physrevc.85.025201

Cited by 57 publications

(117 citation statements)

References 34 publications

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“…In particular, the χ 2 contribution from recent CB@BNL [3] and MAMI-B measurements at 6 overlapped energies [313, 337, 361, 385, 409, and 432 MeV] results χ 2 /data = 97.7/102 = 1.0 and χ 2 /data = 103.9/45 = 2.3, respectively, for the PE12 solution. While for previous SN11 solution [13], it gives χ 2 /data = 87.4/102 = 0.9 and χ 2 /data = 188.6/45 = 4.2, respectively (MAMI-B data had no FSI corrections).…”

Section: Resultsmentioning

confidence: 99%

“…[8]. For the reader convenience these data with the final γn → π − p ones in CM frame, dσ dΩ (γn), are also shown in Tables I and II along with their uncertainties. The χ 2 contribution of MAMI-B data (including FSI corrections) is χ 2 /data = 249.4/104 = 2.4 while, prior to fitting, for SN11 [13] (MAID07 [14]), we had χ 2 /data = 605.8/104 = 5.8 (623.2/104 = 6.0).…”

Section: Resultsmentioning

confidence: 99%

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Evaluation of theγn→π−pdifferential cross section in theΔ-isobar region

et al. 2012

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Evaluation of theγn→π−pdifferential cross section in theΔ-isobar region

et al. 2012

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“…(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].…”

Section: Pacs Numbersmentioning

confidence: 99%

“…1 and 2 with predictions from SAID (SN11 and CM12 [6,7]), MAID [8] and BnGa2011-02 [9]. In addition, a fit to the data within the BnGa-PWA (BnGa2011-02E) is shown.…”

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.

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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...

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“…Practically, the precision of existing data poses the major problem in the extraction of amplitudes. Single-energy solutions have been extracted for many years [77][78][79].…”

Section: Direct-channel Productionmentioning

confidence: 99%

Analysis Tools for Next-Generation Hadron Spectroscopy Experiments

Battaglieri¹,

Briscoe²,

Celentano³

et al. 2015

Acta Phys. Pol. B

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The series of workshops on New Partial-Wave Analysis Tools for Next-Generation Hadron Spectroscopy Experiments was initiated with the ATHOS 2012 meeting, which took place in Camogli, Italy, June 20-22, 2012. It was followed by ATHOS 2013 in Kloster Seeon near Munich, Germany, May 21-24, 2013. The third, ATHOS3, meeting is planned for April 13-17, 2015 at The George Washington University Virginia Science and Technology Campus, USA. The workshops focus on the development of amplitude analysis tools for meson and baryon spectroscopy, and complement other programs in hadron spectroscopy organized in the recent past including the INT-JLab Workshop on Hadron Spectroscopy in Seattle in 2009, the International Workshop on Amplitude Analysis in Hadron Spectroscopy at the ECT*-Trento in 2011, the School on Amplitude Analysis in Modern Physics in Bad Honnef in 2011, the Jefferson Lab Advanced Study Institute Summer School in 2012, and the School on Concepts of Modern Amplitude Analysis Techniques in Flecken-Zechlin near Berlin in September 2013. The aim of this document is to summarize the discussions that took place at the ATHOS 2012 and ATHOS 2013 meetings. We do not attempt a comprehensive review of the field of amplitude analysis, but offer a collection of thoughts that we hope may lay the ground for such a document.Comment: 28 pages, 11 figures, proceedings of the ATHOS 2012 and ATHOS 2013 meeting

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Updated SAID analysis of pion photoproduction data

Cited by 57 publications

References 34 publications

Evaluation of theγn→π−pdifferential cross section in theΔ-isobar region

Evaluation of theγn→π−pdifferential cross section in theΔ-isobar region

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

Analysis Tools for Next-Generation Hadron Spectroscopy Experiments

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