Eta Photoproduction Off the Neutron at Graal

Kuznetsov, V.; Bartalini, O.; Bellini, V.; Castoldi, M.; D’Angelo, A.; Didélez, J. P.; Salvo, R. Di; Fantini, A.; Franco, D.; Gervino, G.; Ghio, F.; Girolami, B.; Giusa, A.; Guidal, M.; Hourany, E.; Kunne, R.; Lapik, A.; Sandri, P. Levi; Moricciani, D.; Nicoletti, L.; Randieri, C.; Rudnev, N.; Russo, G.; Schaerf, C.; Sperduto, M. L.; Sutera, M. C.; Turinge, A.

doi:10.1142/9789812773333_0045

Cited by 10 publications

(28 citation statements)

References 5 publications

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“…Note that exactly the same self-consitent formalism and numerical methods are used in the present work. With this formalism used, we can describe pentaquark observables on the same ground as those for the octet baryons without doing any additional conceptual changes and using the same parameter set.In addition to the Θ + , a recent GRAAL experiment [21,22,23] has announced a new finding of the nucleon-like resonance around 1.67 GeV in the neutron channel, measuring the cross section of η photoproduction off the deutron. The corresponding width was found…”

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confidence: 99%

Axial-vector transitions and strong decays of the baryon antidecuplet in the self-consistent SU(3) chiral quark-soliton model

2008

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We investigate the axial-vector transition constants of the baryon antidecuplet to the octet and decuplet within the framework of the self-consistent SU(3) chiral quark-soliton model. Taking into account rotational 1/N c and linear m s corrections and using the symmetry-conserving quantization, we calculate the axial-vector transition constants. It is found that the leading-order contributions are generally almost canceled by the rotational 1/N c corrections. Thus, the m s corrections turn out to be essential contributions to the axial-vector constants. The decay width of the Θ + → N K transition is determined to be Γ(Θ → N K) = 0.71 MeV, based on the result of the axialvector transition constant g * A (Θ → N K) = 0.05. In addition, other strong decays of the baryon antidecuplet are investigated.Since the LEPS collaboration announced the evidence of the Θ + existence [1], which was motivated by Ref. [2] where its decay width was predicted to be very small with its mass 1540 MeV [3] as well, there has been a great deal of experimental and theoretical work on the Θ + (see, for example, reviews [4,5] for the experimental and theoretical status before 2006). However, a series of very recent experiments conducted by the CLAS collaboration reported null results of finding the Θ + [6,7,8,9] in various reactions. These CLAS experiments were dedicated ones with high statistics. The null results of the CLAS experiment imply that the total cross sections for photoproductions of the Θ + are tiny. In fact, the 95% CL upper limits on the total production cross sections for the Θ + at 1540 MeV lie mostly in the range of of 0.3 − 0.8 nb [6,7,9]. In Ref.[8] the 95 % CL upper limit on the γd → ΛΘ + total cross section is set to be 5 nb in the mass range between 1.52 and 1.56 GeV/c 2 . The KEK-PS E522 collaboration [10] has performed the experiment searching for the Θ + in the π − p → K − X reaction and found a bump at 1530 MeV/c 2 but with only (2.5 − 2.7) σ statistical significance. The upper limit of Θ + production cross section in the π − p → K − Θ + reaction was extracted to be 3.9µb. A later sequential experiment at KEK, however, has observed no clear peak structure in the K + p → π + X reaction [11], giving a 95 % CL upper limit of 3.5 µb/sr on the differential cross section averaged over 2 • to 22 • .In the meanwhile, the DIANA collaboration has continued to search for the Θ + in the K + n → K 0 p reaction and has found a direct formation of a narrow pK 0 peak with mass of 1537 ± 2 MeV/c 2 and width of Γ = 0.36 ± 0.11 MeV [12]. Note that the former measurement by the DIANA collaboration for the Θ + has yielded the mass of the Θ + 1539 ± 2 MeV/c 2 with the decay width Γ ≤ 9 MeV [13]. The SVD experiment has also announced a narrow peak with the mass M = 1523 ± 2(stat.) ± 3(syst.) MeV/c 2 in the inclusive reaction pA → pK 0 s + X [14,15]. The LEPS collaboration also brings about positive new results indicating the existence of the Θ + [16,17].Theoretically, it is of great importance to understand why the Θ + is rather elusive....

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Axial-vector transitions and strong decays of the baryon antidecuplet in the self-consistent SU(3) chiral quark-soliton model

2008

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“…1. We made very simple analysis of that phenomena using "speed characteristics" (6) in order to single out "rapid" contributions on the background of smooth contributions of known wide resonances. Our analysis showed that the data of [26] may indicate an existence of new narrow N * (1685) resonance with Γ tot ≤ 50 MeV and small resonance photocoupling in the range of Br ηN A p 1/2 ∼ (0.3 − 3) · 10 −3 GeV −1/2 .…”

Section: Discussionmentioning

confidence: 99%

“…Recently four groups -GRAAL [6,7], CBELSA/TAPS [8], LNS [9], and Crystal Ball/TAPS [10] -reported an evidence for a narrow structure at W ∼ 1680 MeV in the η photoproduction on the neutron. The structure was observed as a bump in the quasi-free cross section (the neutron anomaly * ) and as a peak in the invariant-mass spectrum of the final-state η and the neutron (M(ηn)) [7,8,10].…”

Section: Introduction To the Neutron Anomalymentioning

confidence: 99%

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On narrow nucleon excitation N*(1685)

2011

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We collected notes and simple estimates about putative narrow nucleon N * (1685)-the candidate for the non-strange member of the exotic anti-decuplet of baryons. In particular, we consider the recent high precision data on η photoproduction off free proton obtained by the Crystal Ball Collaboration at MAMI. We show that it is difficult to describe peculiarities of these new data in the invariant energy interval of W ∼ 1650 − 1750 MeV in terms of known wide resonances. Using very simple estimates, we show that the data may indicate an existence of a narrow N * (1685) with small photocoupling to the proton.

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“…In addition to Θ + , Kuznetsov et al [16][17][18] discovered a new nucleon-like resonance around 1.67 GeV from η photoproduction off the deutron in the neutron channel, based on the GRAAL data. The decay width was measured to be around 40 MeV.…”

Section: Introductionmentioning

confidence: 99%

Mass splittings of the baryon decuplet and antidecuplet with second-order flavor symmetry breakings within a chiral soliton model

Yang

Kim

2012

Journal of the Korean Physical Society

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We revisit the mass splittings of SU(3) baryons, taking into account the second-order effects of isospin and SU(3) flavor symmetry breakings within the framework of a chiral soliton model. The masses of the baryon decuplet turn out to be improved, compared to those with the first-order corrections. The mass of the N * as a member of the baryon antidecuplet is obtained as Mn * = 1687 MeV, which is in agreement with the recent experimental data. The pion-nucleon sigma term becomes ΣπN = (50.5 ± 5.4) MeV.

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Eta Photoproduction Off the Neutron at Graal

Cited by 10 publications

References 5 publications

Axial-vector transitions and strong decays of the baryon antidecuplet in the self-consistent SU(3) chiral quark-soliton model

Axial-vector transitions and strong decays of the baryon antidecuplet in the self-consistent SU(3) chiral quark-soliton model

On narrow nucleon excitation N*(1685)

Mass splittings of the baryon decuplet and antidecuplet with second-order flavor symmetry breakings within a chiral soliton model

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