Photoproduction of $\eta$ -mesons on protons in the resonance region: The background problem and the third S 11-resonance

Tryasuchev, V. A.

doi:10.1140/epja/i2004-10024-x

Cited by 23 publications

(29 citation statements)

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“…[12−13] this resonance is shown to be insignificant, whereas in more recent works of [14−16] quite essential contribution of P 13 (1720) has been reported. Here we would like to mention that important role of this resonance in the reaction (1) has also been pointed out in our previous works (see, e.g., [7]). The three resonances…”

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confidence: 75%

“…[6−10]. After the GRAAL measurements of beam asymmetry and differential cross sections in the energy region 1100−1500 MeV were reported, necessity of essential revision of the resonance properties collected in [7,10] has become evident.In order to explain all the available data for the reaction (1), new S 11 resonance with quite definite position on the complex energy plane was required in addition to the already known baryons S 11 (1535) and S 11 (1650). Information on three S 11 -resonances obtained in our works is presented in Table 1.…”

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Final remarks to our study of $ \eta$ -photoproduction on protons in the resonance region

Tryasuchev

2008

Eur. Phys. J. A

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The properties of previously discovered nucleon resonances are amended basing on the recent and more detailed experimental data about photoproduction of η-mesons on protons. 25.20.Lj, 13.60.Le, 14.20.Gk. As the experimental data on η-photoproduction on nucleons have been accumulated [1−5] they were gradually analyzed within dynamical models developed in refs. [6−10]. After the GRAAL measurements of beam asymmetry and differential cross sections in the energy region 1100−1500 MeV were reported, necessity of essential revision of the resonance properties collected in [7,10] has become evident.In order to explain all the available data for the reaction (1), new S 11 resonance with quite definite position on the complex energy plane was required in addition to the already known baryons S 11 (1535) and S 11 (1650). Information on three S 11 -resonances obtained in our works is presented in Table 1. Here, β stands for the sign of the ratio of ηNR and πNR couplings. The properties of all resonances, needed to describe the measured observables of the process (1), are listed in Table 2. There, the absolute values ξ λ [11] are proportional to the contributions of the corresponding resonances to the reaction (1). As one can see, the contribution of P 13 (1720) appears to be very important. This resonance strongly influences the shape of angular distributions as well as beam asymmetry in a wide energy region up to 1.9 GeV. By now, opinions differ widely on the role of the baryon P 13 (1720) in η-photoproduction. For example, in refs. [12−13] this resonance is shown to be insignificant, whereas in more recent works of [14−16] quite essential contribution of P 13 (1720) has been reported. Here we would like to mention that important role of this resonance in the reaction (1) has also been pointed out in our previous works (see, e.g., [7]). The three resonancesare shown to be less significant, but their inclusion results in better description of the structural details of the observed cross section.As for the heavier resonancesamong which the last three are marked with four stars in the PDG compilation [17], we found that G 19 (2250) provides only small fraction of the resulting cross section. The other resonances, being much more important, govern the shape of η angular distributions at photon energies K 0 > 1.5 GeV. At the same time, the masses and widths of these states are not uniquely determined. Polarization measurements in the appropriate energy region are necessary for a more precise determination of these parameters. Several results coming out from our analysis seem to be unrealistic and need further clarification. Firstly, the S 11 (1650) photoexcitation amplitude has too large magnitude which appears to be comparable to that of S 11 (1535) (see Table 1). Secondly, our model favors equal values of the electromagnetic amplitudes for F 15 (1680)This paper is in contradiction with the average PDG results [17], where A 1/2 << A 3/2 . We did not show our calculation for photon energies below 930 MeV, since...

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Final remarks to our study of $ \eta$ -photoproduction on protons in the resonance region

Tryasuchev

2008

Eur. Phys. J. A

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“…To describe the observable quantities of the process under consideration, the authors of [8] involved eleven nucleon resonances, and the cross sections have been calculated for the photon energies from the reaction threshold to K 0 = 3 GeV owing to the inclusion of the heavy "4-star" resonances F 17 (1990), G 17 (2190), G 19 (2250), and H 19 (2220 [9]. The parameters of these resonances were varied in the ranges recommended by the authors of [9] and were chosen for reasons of the best description of only low-energy (K 0 ≤ 2 GeV) data, since at that time "precise" measurements at higher energies were absent.…”

Section: γP → ηP For Photon Energies Above 2 Gevmentioning

confidence: 99%

“…The parameters of these resonances were varied in the ranges recommended by the authors of [9] and were chosen for reasons of the best description of only low-energy (K 0 ≤ 2 GeV) data, since at that time "precise" measurements at higher energies were absent. Besides the resonances, the amplitude of the process (1) in [8] included the nucleon and meson (ρ, ω) currents. New experimental data about the process (1) obtained at higher energies, K 0 ≈ 2−3 GeV [10], enables one to check up the predictions of former models and, if necessary, to carry out their correction.…”

Section: γP → ηP For Photon Energies Above 2 Gevmentioning

confidence: 99%

“…New experimental data about the process (1) obtained at higher energies, K 0 ≈ 2−3 GeV [10], enables one to check up the predictions of former models and, if necessary, to carry out their correction. In this paper, we compare the predictions of the model proposed in [8] with recently measured differential cross sections and correct this model by varying the contributions of heavy resonances to the amplitude. As can be seen from Figs.…”

Section: γP → ηP For Photon Energies Above 2 Gevmentioning

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Contributions of high-spin resonances to the reaction γp → ηp for photon energies above 2 GeV

Tryasuchev

2006

Russ Phys J

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It is well known that in reactions of the type γN → ηN only the currents of nucleon resonances with the isospin I = 1/2 are possible; therefore, these reactions are most suitable for studying the properties of resonances of this type. Dynamic models of the processhave been constructed by the authors of [1-8] based on the experimental data obtained for photon energies K 0 below 2 GeV.To describe the observable quantities of the process under consideration, the authors of [8] involved eleven nucleon resonances, and the cross sections have been calculated for the photon energies from the reaction threshold to K 0 = 3 GeV owing to the inclusion of the heavy "4-star" resonances F 17 (1990), G 17 (2190), G 19 (2250), and H 19 (2220 [9]. The parameters of these resonances were varied in the ranges recommended by the authors of [9] and were chosen for reasons of the best description of only low-energy (K 0 ≤ 2 GeV) data, since at that time "precise" measurements at higher energies were absent. Besides the resonances, the amplitude of the process (1) in [8] included the nucleon and meson (ρ, ω) currents. New experimental data about the process (1) obtained at higher energies, K 0 ≈ 2−3 GeV [10], enables one to check up the predictions of former models and, if necessary, to carry out their correction. In this paper, we compare the predictions of the model proposed in [8] with recently measured differential cross sections and correct this model by varying the contributions of heavy resonances to the amplitude. As can be seen from Figs. 1 and 2, the cross sections for this reaction measured in [10] at an energy of photons below 2 GeV agree with the earlier measured cross sections [11][12][13]. For the calculated cross sections to agree with the results of the last experiment, it was necessary to use in this model only two of the four heavy resonances: G 17 (2190) and H 19 (2220). The results of calculations by the so updated model with nine nucleon resonances are shown in Figs. 1 and 2 by curves 1 and 2.

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Chiral constituent quark model study of the process γp → ηp

He¹,

Saghai²,

Li³

et al. 2008

Nstar 2007

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Within a chiral constituent quark model approach, η-meson production on the proton via electromagnetic and hadron probes are studied. With few parameters, differential crosssection and polarized beam asymmetry for γp → ηp and differential cross section for π − p → ηn processes are calculated and successfully compared with the data in the centerof-mass energy range from threshold up to 2 GeV. The five known resonances S 11 (1535), S 11 (1650), P 13 (1720), D 13 (1520), and F 15 (1680) are found to be dominant in the reaction mechanisms in both channels. Possible roles plaied by new resonances are also investigated and in the photoproduction channel, significant contribution from S 11 -and D 15 -resonances, with masses around 1715 MeV and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of N * → πN, ηN are also presented, and found consistent with the PDG values.both differential cross section [2, 3,4,5], and polarized beam asymmetry [5,6]. The situation is very different for the π − p → ηn reaction. Actually, the data come mainly from measurements performed in 70's [7,8,9,10,11,12] and suffer from some inconsistencies [13]. A recent experiment, performed at BNL using the Crystal Ball spectrometer [14], offers a high quality data set, though limited to the close to threshold kinematics. Consequently, a combined data base embodying experimental results for both electromagnetic and strong channels turns out to be highly heterogeneous. In spite of that uncomfortable situation, recent intensive theoretical investigations interpreting both channels within a single approach has proven to be fruitful in revealing various aspects of the relevant reaction mechanisms, as discussed, e.g., in Refs. [1,15].In the photoproduction sector, a significant progress has been performed in recent years within coupled-channels formalisms [16,17,18,19] allowing to investigate a large number of intermediate and/or final meson-baryon (MB) states: γN → M B, with M B ≡ πN, ηN, ρN, σN, π∆, KΛ, KΣ.Those approaches have been reviewed in our recent paper [1]. Also advanced coupled-channels approaches are being developed [15,20,21,22] for the strong channels: πN → M B. However, fewer studies embody both electromagnetic and strong production processes. Moreover, those works are based on the effective Lagrangian approaches (ELA), where meson-baryon degrees of freedom are implemented, (see e.g. Refs. [17,18,23,24]). Investigations based on subnucleonic degrees of freedom, via constituent quark models (CQM) have been successful [1,25,26,27,28,29] in the interpretation of photoproduction data on the proton, namely, γp → πN, ηp, KΛ, and a recent work [30] has considered the π − p → ηn reaction.At the present stage, the ELA and the CQM approaches are complementary. However, the QCDinspired CQM developments deal on the one hand with more fundamental degrees of freedom and on the other hand require a much smaller number of adjustable p...

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Photoproduction of $\eta$ -mesons on protons in the resonance region: The background problem and the third S 11-resonance

Cited by 23 publications

References 24 publications

Final remarks to our study of $ \eta$ -photoproduction on protons in the resonance region

Final remarks to our study of $ \eta$ -photoproduction on protons in the resonance region

Contributions of high-spin resonances to the reaction γp → ηp for photon energies above 2 GeV

Chiral constituent quark model study of the process γp → ηp

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