Toward complete pion nucleon amplitudes

Mathieu, V.; Danilkin, Igor; Fernández-Ramírez, C.; Pennington, M.R.; Schott, D.; Szczepaniak, Adam P.; Fox, Geoffrey

doi:10.1103/physrevd.92.074004

Cited by 33 publications

(48 citation statements)

References 45 publications

(50 reference statements)

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“…This theoretical expectation should in principle be verified, for example via FESR. For example, a wrong signature zero is present in the ρ pole amplitude in pion-nucleon scattering and consistent with FESR [30]. This zero implies a dip in the differential cross section in π − p → π 0 n. The dip in γp → π 0 p was therefore also assumed to come from the wrong signature zero.…”

Section: Fitting Proceduresmentioning

confidence: 99%

Neutral pion photoproduction in a Regge model

2015

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The reaction γp → π 0 p is investigated in the energy range above the resonance region. The amplitudes include the leading Regge singularities in the cross-channel and correctly describe the differential cross section for beam energies above 4 GeV and for the s−channel scattering angle cos θs ≥ 0.6. The energy dependence of the beam asymmetry and the reaction γn → π 0 n seem is quantitative consistent with the Regge-pole dominance.

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Section: Fitting Proceduresmentioning

confidence: 99%

Neutral pion photoproduction in a Regge model

2015

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“…In high-energy photoproduction, the dominant meson production mechanism at small momentum transfer is expected to be the exchange of massive quasi-particles known as Reggeons [1]. Interest in this theoretical description of highenergy photoproduction has increased recently, as it provides constraints on the quantum mechanical amplitudes utilized in low-energy meson photoproduction to extract the spectrum of excited baryons [2], which depend strongly on the internal dynamics of the underlying constituents [3]. In addition, understanding the meson photoproduction mechanism at high energies is a vital component of a broader program to search for gluonic excitations in the meson spectrum through photoproduction reactions, which is the primary goal of the GLUEX experiment at Jefferson Lab.…”

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confidence: 99%

Measurement of the beam asymmetry Σ for π0 and η photoproduction on the proton at Eγ
Ghoul¹,
Anassontzis²,
Austregesilo³
et al. 2017
Phys. Rev. C
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68
5
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0
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We report measurements of the photon beam asymmetry Σ for the reactions γp → pπ 0 and γp → pη from the GLUEX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous π 0 measurements and are the first η measurements in this energy regime. The results are compared with theoretical predictions based on t-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.

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“…For example, the analysis based on Roy-Steiner equations [20] has reproduced low-energy phase shift data successfully (see also Refs. [21,22]). More recently, in Ref.[23], low-energy πN scattering has been re-visited with the help of the Peking University (PKU) representation [24-27] -a production parametrization of the unitary partial wave S matrix for two-body elastic scattering amplitudes.…”

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On the existence of N*(890) resonance in S11 channel of πN scatterings

2018

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Low-energy partial-wave πN scattering data is reexamined with the help of the production representation of partial-wave S matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift is determined, with controlled systematic error estimates, by using the results of O(p 3 ) chiral perturbative amplitudes obtained in the extended-on-mass-shell scheme. In S 11 and P 11 channels, severe discrepancies are observed between the phase shift data and the sum of all known contributions. Statistically satisfactory fits to the data can only be achieved by adding extra poles in the two channels. We find that a S 11 resonance pole locates at √ z r = (0.895 ± 0.081) − (0.164 ± 0.023)i GeV, on the complex s-plane. On the other hand, a P 11 virtual pole, as an accompanying partner of the nucleon bound-state pole, locates at √ z v = (0.966 ± 0.018) GeV, slightly above the nucleon pole on the real axis below threshold. Physical origin of the two newly established poles is explored to the best of our knowledge. It is emphasized that the O(p 3 ) calculation greatly improves the fit quality comparing with the previous O(p 2 ) one.The studies in the field of πN scatterings have led to and fertilized many useful ideas and methods in the development of hadron and even particle physics, such as the establishment of dispersion techniques [1], the concepts of finite energy sum rules [2, 3] and duality [4]. In decades, a wealth of experimental data on differential cross section and polarizations [5] has been accumulated. Partial wave analysis of the πN scattering amplitudes has also been performed which results in the discovery of many baryon resonances [6][7][8][9].Efforts in modern studies on πN scatterings focus on a precision description of the πN amplitudes, not only in the physical region but also in the subthreshold region. Baryon chiral perturbation theory (BChPT) [10-12] serves as an appropriate tool for such a purpose, at low energies. The problem of power counting breaking terms [13] in loops, caused by the presence of baryon degrees of freedom in the chiral Lagrangian, is finally overcome by the use of the extended-on-mass-shell subtraction scheme [14]. Though many achievements have been obtained in the perturbation calculations within this scheme [15][16][17][18][19], analyses respecting both exact partial wave unitarity and proper analyticity are still lacking. Hence the use of the dispersion techniques revived in recent years. For example, the analysis based on Roy-Steiner equations [20] has reproduced low-energy phase shift data successfully (see also Refs. [21,22]).More recently, in Ref.[23], low-energy πN scattering has been re-visited with the help of the Peking University (PKU) representation [24-27] -a production parametrization of the unitary partial wave S matrix for two-body elastic scattering amplitudes. The production representation is constructed from first principles. Especially, analyticity and unitarity are automatically built in, hence the fatal defic...

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Toward complete pion nucleon amplitudes

Cited by 33 publications

References 45 publications

Neutral pion photoproduction in a Regge model

Neutral pion photoproduction in a Regge model

Measurement of the beam asymmetry Σ for π0 and η photoproduction on the proton at Eγ
Ghoul¹,
Anassontzis²,
Austregesilo³
et al. 2017
Phys. Rev. C
Self Cite
68
5
81
0
View full text Add to dashboard Cite

On the existence of N*(890) resonance in S11 channel of πN scatterings

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Toward complete pion nucleon amplitudes

Cited by 33 publications

References 45 publications

Neutral pion photoproduction in a Regge model

Neutral pion photoproduction in a Regge model

Measurement of the beam asymmetry Σ for π0 and η photoproduction on the proton at EγGhoul1, Anassontzis2, Austregesilo3 et al. 2017Phys. Rev. CSelf Cite685810View full textAdd to dashboardCite

On the existence of N*(890) resonance in S11 channel of πN scatterings

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Resources

About

Measurement of the beam asymmetry Σ for π0 and η photoproduction on the proton at Eγ
Ghoul¹,
Anassontzis²,
Austregesilo³
et al. 2017
Phys. Rev. C
Self Cite
68
5
81
0
View full text Add to dashboard Cite