The polarised beam asymmetry in photoproduction of eta mesons from protons at 2.5 GeV and 3.0 GeV

Bussey, P.; Raine, C.; Rutherglen, J.G.; Booth, P.S.L.; Carroll, L.; Daniel, P.R.; Edwards, A.; Hardwick, C.; Holt, J.R.; Jackson, J. N.; Norem, J.; Range, W.H.; Galbraith, W.; Rajaratnam, V.H.; Sutton, C.; Thorne, M C; Waller, P.

doi:10.1016/0370-2693(76)90733-4

Cited by 19 publications

(27 citation statements)

References 14 publications

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“…It is worth mentioning that results from LEPS [199] and older results from the Daresbury facility [287] are in excellent agreement with CBELSA/TAPS at energies above 2 GeV. Precise measurements of polarization observables in η photoproduction are currently only available for the beam asymmetry, Σ.…”

Section: Photoproduction Of Single η and η ′ Mesonsmentioning

confidence: 62%

Progress towards understanding baryon resonances

2013

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Abstract. The composite nature of baryons manifests itself in the existence of a rich spectrum of excited states, in particular in the important mass region 1-2 GeV for the light-flavoured baryons. The properties of these resonances can be identified by systematic investigations using electromagnetic and strong probes, primarily with beams of electrons, photons, and pions. After decades of research, the fundamental degrees of freedom underlying the baryon excitation spectrum are still poorly understood. The search for hitherto undiscovered but predicted resonances continues at many laboratories around the world. Recent results from photo-and electroproduction experiments provide intriguing indications for new states and shed light on the structure of some of the known nucleon excitations. The continuing study of available data sets with consideration of new observables and improved analysis tools have also called into question some of the earlier findings in baryon spectroscopy. Other breakthrough measurements have been performed in the heavy-baryon sector, which has seen a fruitful period in recent years, in particular at the B factories and the Tevatron. First results from the LHC indicate rapid progress in the field of bottom baryons. In this review, we discuss the recent experimental progress and give an overview of theoretical approaches.

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Section: Photoproduction Of Single η and η ′ Mesonsmentioning

confidence: 62%

Progress towards understanding baryon resonances

2013

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“…A comparison between those experimental results [36,37,38,27,28] and our calculation was presented in Ref. [11].…”

Section: The Reaction Amplitudementioning

confidence: 79%

“…The parameters of our Regge model were fixed by a fit to data on η-meson photoproduction data published before 1982 [11]. Specifically, this concerns the differential cross sections collected at SLAC [36], DESY [37], Cornell [38] and at the Daresbury laboratory [27]. All these measurements were done at and above photon energies of E γ =2.5 GeV, which corresponds to an invariant collision energies larger than √ s ≃2.…”

Section: The Reaction Amplitudementioning

confidence: 99%

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Analysis of recent $ \eta$ photoproduction data

et al. 2010

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Recent data on η-meson photoproduction off a proton target in the energy range 2≤ √ s≤3 GeV are analyzed with regard to their overall consistency. Results from the ELSA and CLAS measurements are compared with predictions of a Regge model whose reaction amplitude was fixed via a global fit to pre-2000 measurements of differential cross sections and polarization observables for γp→ηp at higher energies. We find that all recent experimental results on differential cross sections for η-meson photoproduction are in good agreement with each other, except for the CLAS data from 2009. However, the latter can be made consistent with the other data at the expense of introducing an energy-dependent renormalization factor. We point out that there indications in the data for a possible excitation of baryon resonances with masses around 2.1 and 2.4 GeV.PACS. 11.55.Jy Regge formalism -13.60.Le Meson production -13.60.-r Photon and charged-lepton interactions with hadrons -25.20.Lj Photoproduction reactions

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“…Some interesting spin measurements have been performed many years ago, in particular with the aim of determining the spin and parity of new mesons, or to study the reaction mechanism. For instance, Bussey et al [112] measured the beam asymmetry Σ (to be defined shortly) of the reaction γp → ηp at 2.5 and 3 GeV, and found a value close to the maximum allowed, +1, see Fig. 24.…”

Section: Photoproduction Of Scalar or Pseudoscalar Mesons 341 Expermentioning

confidence: 87%

Spin observables and spin structure functions: Inequalities and dynamics

et al. 2009

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Model-independent identities and inequalities which relate the various spin observables of collisions in nuclear and particle physics are reviewed in a unified formalism. Their physical interpretation and their implications for dynamical models are also discussed. These constraints between observables can be obtained in several ways: from the explicit expression of the observables in terms of a set of helicity or transversity amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the spins in the initial or final state of the reaction or its crossed channels. The inequalities resulting from positivity need to be projected to single out correlations between two or three observables. The quantum aspects of the information carried by spins, in particular entanglement, are considered when deriving and discussing the constraints Several examples are given, with a comparison with experimental data in some cases. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and for the simplest observables of single-particle inclusive reactions are reviewed. They also apply to spin-dependent structure functions and parton distributions, both integrated or transverse-momentum dependent. The corresponding inequalities are shown to be preserved by the evolution equations of quantum chromodynamics.Inequalities on spin observables 3

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The polarised beam asymmetry in photoproduction of eta mesons from protons at 2.5 GeV and 3.0 GeV

Cited by 19 publications

References 14 publications

Progress towards understanding baryon resonances

Progress towards understanding baryon resonances

Analysis of recent $ \eta$ photoproduction data

Spin observables and spin structure functions: Inequalities and dynamics

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