N $$^*$$ ∗ Experiments and Their Impact on Strong QCD Physics

Burkert, Volker

doi:10.1007/s00601-018-1378-7

Cited by 18 publications

(16 citation statements)

References 105 publications

(130 reference statements)

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“…These coupled-channel model calculations are performed with the η treated as a pure octet state. In Jefferson Laboratory measurements, the N*(1535) contribution to η electroproduction was observed to fall away more slowly with increasing large Q 2 (up to about 7 GeV 2 ) than expected for a meson-baryon bound system (Armstrong et al, 1999;Aznauryan and Burkert, 2012;Burkert, 2018;Dalton et al, 2009). This suggests a significant 3-quark contribution.…”

Section: η-And η -Nucleon Interactionsmentioning

confidence: 84%

η′ and η mesons with connection to anomalous glue

Bass

Moskal

2019

Rev. Mod. Phys.

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We review the present understanding of η and η meson physics and these mesons as a probe of gluon dynamics in low-energy QCD. Recent highlights include the production mechanism of η and η mesons in proton-nucleon collisions from threshold to high-energy, the η effective mass shift in the nuclear medium, searches for possible η and η bound states in nuclei as well as precision measurements of η decays as a probe of light-quark masses. We discuss recent experimental data, theoretical interpretation of the different measurements and the open questions and challenges for future investigation.

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Section: η-And η -Nucleon Interactionsmentioning

confidence: 84%

η′ and η mesons with connection to anomalous glue

Bass

Moskal

2019

Rev. Mod. Phys.

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“…As illustrated in figure. 1, this kinematical region is complementary to the space-like region (q 2 <0) probed in electron scattering, in particular with the CLAS detector at JLab [6]. The two regions are connected at the "photon point" (q 2 =0), where information on the N-γ couplings is provided by meson photoproduction experiments.…”

Section: Dalitz Decay Studies With Hadesmentioning

confidence: 94%

Studying time-like electromagnetic baryonic transitions with HADES in pion induced reactions

Ramstein¹

2020

EPJ Web Conf.

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A dedicated programme aiming at studying electromagnetic baryonic transitions in the time-like region has started at GSI using the pion beam and the High Acceptance Di-Electron Spectrometer (HADES) set-up. A pioneering experiment has been carried out in the second resonance region, at a center-of-mass energy of 1.49 GeV, using carbon and polyethylene targets, allowing for an analysis of the inclusive e+e- production and of the exclusive quasi-free π-p → ne+e- reaction, in complement to hadronic channels. Predictions for the Dalitz decay of N(1520) and N(1535) based on real photon couplings strongly underestimate the e+e- yield at invariant masses larger than 300 MeV/c2, which signals effects of time-like baryon transition form factors, in qualitative agreement with the Vector Dominance Models (VDM). A quantitative description of the observed e+e- yield is achieved by taking into account the contribution from off-shell ρs. The latter was provided by the preliminary results of a Bonn-Gatchina Partial Wave Analysis of the two-pion production channels, which were measured simultaneously in our experiment. A good agreement is also obtained using a covariant model for the time-like electromagnetic form factors for the N-N(1520) transition. The angular distributions for the e+e- production contain additional selective information on the spin structure of the different transitions. The measurements with the pion beam will be extended in future in the third resonance region. Hyperon Dalitz decay studies in proton induced reactions are also foreseen.

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“…On the other hand, by exploiting intense, energetic electron-beams at the Thomas Jefferson National Accelerator Facility, γ * p → ∆ + data are now available for 0 ≤ Q 2 8 GeV 2 [5][6][7]. These data have stimulated much theoretical analysis and speculation about, inter alia: the relevance of perturbative QCD (pQCD) to processes involving moderate momentum transfers [6][7][8][9][10][11][12][13][14]; hadron shape deformation [10][11][12][13][14][15][16][17][18]; and the role that resonance electroproduction experiments can play in exposing nonperturbative aspects of QCD, such as the nature of confinement and dynamical chiral symmetry breaking (DCSB) [7,[19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Transition form factors: γ*+p→Δ(1232) , Δ

Chen

Cui

et al. 2019

Phys. Rev. D

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Electroproduction form factors describing the γ * p → ∆ + (1232), ∆ + (1600) transitions are computed using a fully-dynamical diquark-quark approximation to the Poincaré-covariant three-body bound-state problem in relativistic quantum field theory. In this approach, the ∆(1600) is an analogue of the Roper resonance in the nucleon sector, appearing as the simplest radial excitation of the ∆(1232). Precise measurements of the γ * p → ∆ + (1232) transition already exist on 0 ≤ Q 2 8 GeV 2 and the calculated results compare favourably with the data outside the meson-cloud domain. The predictions for the γ * p → ∆ + (1600) magnetic dipole and electric quadrupole transition form factors are consistent with the empirical values at the real photon point, and extend to Q 2 ≈ 6m 2 p , enabling a meaningful direct comparison with experiment once analysis of existing data is completed. In both cases, the electric quadrupole form factor is particularly sensitive to deformation of the ∆-baryons. Interestingly, whilst the γ * p → ∆ + (1232) transition form factors are larger in magnitude than those for γ * p → ∆ + (1600) in some neighbourhood of the real photon point, this ordering is reversed on Q 2 2m 2 p , suggesting that the γ * p → ∆ + (1600) transition is more localised in configuration space.

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N $$^*$$ ∗ Experiments and Their Impact on Strong QCD Physics

Cited by 18 publications

References 105 publications

η′ and η mesons with connection to anomalous glue

η′ and η mesons with connection to anomalous glue

Studying time-like electromagnetic baryonic transitions with HADES in pion induced reactions

Transition form factors: γ*+p→Δ(1232) , Δ

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