Nucleon resonances with double polarization observables of pion photoproduction

Dutta, D.; H, Gao; Lee, T.-S. H.

doi:10.1103/physrevc.65.044619

Cited by 10 publications

(10 citation statements)

References 11 publications

(26 reference statements)

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“…To make progress, we follow the phenomenological procedure of Ref. [49] to define t γN,πN in terms of the empirical γN → πN amplitude and the resonant amplitude constructed from the quark model predictions of Ref. [27,28,29].…”

Section: A Coupled-channel Formalismmentioning

confidence: 99%

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Dynamical coupled-channels approach to hadronic and electromagnetic kaon-hyperon production on the proton

et al. 2006

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A dynamical coupled-channel formalism for processes πN → KY and γN → KY is presented which provides a comprehensive investigation of recent data on the γp → K + Λ reaction. The nonresonant interactions within the subspace KY ⊕ πN are derived from effective Lagrangians, using a unitary transformation method. The calculations of photoproduction amplitudes are simplified by casting the coupled-channel equations into a form such that the empirical γN → πN amplitudes are input and only the parameters associated with the KY channel are determined by performing χ 2 -fits to all of the available data for π − p → K • Λ, K • Σ • and γp → K + Λ. Good agreement between our models and those data are obtained. In the fits to πN → KY channels, most of the parameters are constrained within ±20% of the values given by the Particle Data Group and/or quark model predictions, while for γp → K + Λ parameters, ranges compatible with broken SU (6)⊗ O(3) symmetry are imposed. The main reaction mechanisms in K + Λ photoproduction are singled out and issues related to newly suggested resonances S 11 , P 13 , and D 13 are studied. Results illustrating the importance of using a coupled-channel treatment are reported. Meson cloud effects on the γN → N * transitions are also discussed.

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Section: A Coupled-channel Formalismmentioning

confidence: 99%

“…where t QM,R πN,γN is the quark model amplitude given explicitly in Ref. [49] and T SAID πN,γN is obtained from the 1995 solution of the SAID [37] analysis. As an alternative, we can replace t QM,R πN,γN by t PDG,R πN,γN which is the γN → N * → πN amplitude defined by the resonance parameters listed by PDG.…”

Section: A Coupled-channel Formalismmentioning

confidence: 99%

Dynamical coupled-channels approach to hadronic and electromagnetic kaon-hyperon production on the proton

et al. 2006

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“…[8,34,69]. The asymmetries are of great interest in the search of missing resonances which do not show up so clearly in other observables [70]. The formulae which relate the amplitudes with the asymmetries will be presented in forthcoming paragraphs.…”

Section: Differential Cross Sections and Asymmetriesmentioning

confidence: 99%

Effective Lagrangian Approach to pion photoproduction from the nucleon

2006

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We present a pion photoproduction model on the free nucleon based on an Effective Lagrangian Approach (ELA) which includes the nucleon resonances ($\Delta(1232)$, N(1440), N(1520), N(1535), $\Delta (1620)$, N(1650), and $\Delta (1700)$), in addition to Born and vector meson exchange terms. The model incorporates a new theoretical treatment of spin-3/2 resonances, first introduced by Pascalutsa, avoiding pathologies present in previous models. Other main features of the model are chiral symmetry, gauge invariance, and crossing symmetry. We use the model combined with modern optimization techniques to assess the parameters of the nucleon resonances on the basis of world data on electromagnetic multipoles. We present results for electromagnetic multipoles, differential cross sections, asymmetries, and total cross sections for all one pion photoproduction processes on free nucleons. We find overall agreement with data from threshold up to 1 GeV in laboratory frame.Comment: Misprints corrected. 60 pages. 33 figures.5 tables. Accepted for publication in Annals of Physics (NY

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“…Whatever the origin is for the observed enhancement around 2.2 GeV, it is remarkable that the scaled differential cross section drops by a factor of 4 over a rather small centerof-mass energy range (∼ 0.3 GeV). More experimental work, such as polarization measurements [40], together with an extended SAID model might help to understand the exact nature of the observed enhancement.…”

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confidence: 99%

Cross-Section Measurement of Charged-Pion Photoproduction from Hydrogen and Deuterium

Zhu¹,

Arrington²,

Averett³

et al. 2003

Phys. Rev. Lett.

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We have measured the differential cross section for the γn → π − p and γp → π + n reactions at θcm = 90 • in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at Eγ 3.3 GeV exhibit a global scaling behavior for both π − and π + photoproduction, consistent with the constituent counting rule and the existing π + photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive π − to π + photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.PACS numbers: 13.60. Le, 24.85.+p, 25.10.+s, The study of the transition region from nucleon-meson degrees of freedom to quark-gluon degrees of freedom in quantum chromodynamics (QCD) for exclusive processes is one of the most interesting subjects in nuclear physics. Scaling in the differential cross section dσ/dt, and hadron helicity conservation have been pursued experimentally as signatures of this transition for years. While global scaling behavior has been observed in many exclusive processes, no experimental evidence supports hadron helicity conservation. Furthermore, the exact nature governing the onset of the scaling behavior is not clear. The relatively large cross section of pion photoproduction allows the search for additional possible signatures: QCD oscillations and the charged pion cross section ratio. In this experiment, three signatures (scaling, QCD oscillations, charged pion ratio) for the transition are investigated.For an exclusive two-body reaction AB → CD at high energy and large momentum transfer, the constituent counting rule (or the dimensional scaling law) predicts [1]where s and t are the Mandelstam variables. The quantity n is the total number of interacting elementary fields in the reaction, and f (θ cm ) is the angular dependence of the differential cross section. This rule was originally derived from dimensional analysis [1], and later confirmed within the framework of a perturbative QCD (pQCD) analysis up to a logarithmic factor of the strong coupling constant α s [2]. Many exclusive measurements at

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Nucleon resonances with double polarization observables of pion photoproduction

Cited by 10 publications

References 11 publications

Dynamical coupled-channels approach to hadronic and electromagnetic kaon-hyperon production on the proton

Dynamical coupled-channels approach to hadronic and electromagnetic kaon-hyperon production on the proton

Effective Lagrangian Approach to pion photoproduction from the nucleon

Cross-Section Measurement of Charged-Pion Photoproduction from Hydrogen and Deuterium

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