Measurements of the γ*p → Δ reaction at low Q2

Sparveris, N.; Stave, S.; Achenbach, P.; Gayoso, C. Ayerbe; Baumann, D.; Bernauer, J. C.; Bernstein, A. M.; Böhm, R.; Bosnar, D.; Botto, T.; Christopoulou, Aikaterini; Dale, D.; Ding, M.; Distler, M. O.; Doria, L.; Jm, Friedrich; Karabarbounis, A.; Makek, M.; Merkel, H.; Müller, U.; Nakagawa, I.; Neuhausen, R.; Nungesser, L.; Papanicolas, C. N.; Piegsa, A.; Pochodzalla, J.; Potokar, M.; Seimetz, M.; Širca, S.; Stiliaris, S.; Walcher, Th.; Weis, M.

doi:10.1140/epja/i2013-13136-2

Cited by 21 publications

(23 citation statements)

References 48 publications

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“…The database from Ref. [22] include data from CLAS [23] and low-Q 2 data from different sources such as MAMI [30], MIT-Bates [31,34] and data at Q 2 = 0 from PDG [26]. In the present study, however, we replaced the data for Q 2 < 0.15 GeV 2 by more recent estimates of the data.…”

Section: Based On the Previous Result One Obtainsmentioning

confidence: 99%

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Low- Q2 empirical parametrizations of the N* helicity amplitudes

Ramalho

2019

Phys. Rev. D

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The data associated with the electromagnetic excitations of the nucleon (γ * N → N * ) is usually parametrized by helicity amplitudes at the resonance N * rest frame. The properties of the γ * N → N * transition current at low Q 2 can be, however, better understood when expressed in terms of structure form factors, particularly near the pseudothreshold, when the magnitude of the photon three-momentum vanishes (|q| = 0). At the pseudothreshold the invariant four-momentum square became q 2 = (MR−MN ) 2 , well in the timelike region Q 2 = −q 2 < 0 [MN and MR are the mass of the nucleon and of the resonance, respectively]. In the helicity amplitude representation, the amplitudes have well defined dependences on |q|, near the pseudothreshold, and there are correlations between different amplitudes. Those constraints are often ignored in the empirical parametrizations of the helicity amplitudes. In the present work we show that the structure of the transition current near the pseudothreshold has an impact on the parametrizations of the data. We present a method which modifies analytic parametrizations of the data at low Q 2 , in order to take into account the constraints of the transition amplitudes near the pseudothreshold. The model dependence of the parametrizations on the low-Q 2 data is studied in detail.

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Section: Based On the Previous Result One Obtainsmentioning

confidence: 99%

“…As for the Q 2 < 0.15 GeV 2 data, we replace the results from MAMI and MIT-Bates (Q 2 = 0.06 and 0.127 GeV 2 ) [30,31,34] by the recent results from JLab/Hall Refs. [26,28].…”

Section: Based On the Previous Result One Obtainsmentioning

confidence: 99%

Low- Q2 empirical parametrizations of the N* helicity amplitudes

Ramalho

2019

Phys. Rev. D

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“…found in those for E0 and M1. 12 T3 ∆|D (8) 8i Ji|∆ = Σ * |D (8) 8i Ji|Σ * = Ξ * |D (8) 8i Ji|Ξ * = Ω|D (8) 8i Ji|Ω = − 5 √ 3 16 Y ∆|D (8) 3i Ji|∆ = Σ * |D (8) 3i Ji|Σ * = Ξ * |D (8) 3i Ji|Ξ * = Ω|D (8) 3i Ji|Ω = − 5 8 T3 ∆|D (8) 8a Ja|∆ = Σ * |D (8) 8a Ja|Σ * = Ξ * |D (8) 8a Ja|Ξ * = Ω|D (8) 8a Ja|Ω = − √ 3 8 Y ∆|D (8) 3a Ja|∆ = Σ * |D (8) 3a Ja|Σ * = Ξ * |D (8) 3a Ja|Ξ * = Ω|D (8) 3a Ja|Ω = − 1 4 T3 The densities of the electric quadrupole form factors are given as…”

Section: Discussionmentioning

confidence: 99%

“…By the turn of the new century, however, being equipped with a new generation of electron beam accelerators and detectors with high precision, one was able to take a better grasp of the EM transitions of ∆ isobars [3,4]. For example, various experimental groups have announced the results on the γ * N → ∆ excitation: the Laser Electron Gamms Source (LEGS) Collaboration at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory [5][6][7], the CLAS Collaboration [8][9][10] at Jefferson Laboratory, and the A1 and A2 Collaborations [11][12][13][14][15][16] at MAMI. The EM structure of the strangeness members of the baryon decuplet has been also experimentally investigated at these experimental facilities.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic form factors of the baryon decuplet with flavor SU(3) symmetry breaking

Kim

2019

Eur. Phys. J. C

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We investigate the electromagnetic form factors of the baryon decuplet within the framework of the SU(3) self-consistent chiral quark-soliton model, taking into account the 1/Nc rotational corrections and the effects of flavor SU(3) symmetry breaking. We first examine the valence-and sea-quark contributions to each electromagnetic form factor of the baryon decuplet and then the effects of the flavor SU(3) symmetry breaking. The present results are in good agreement with the recent lattice data. We also compute the charge radii, the magnetic radii, the magnetic dipole moments and the electric quadrupole moments, comparing their results with those from other theoretical works. We also make a chiral extrapolation to compare the present results with the lattice data in a more quantitative manner. The results show in general similar tendency to the lattice results. In particular, the results of the M 1 and E2 form factors are in good agreement with those of lattice QCD.

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“…Except for the Ω − baryon, all the members of the baryon decuplet decay strongly, so that it is extremely difficult to measure the EM form factors of the baryon decuplet. Nevertheless, using the electron and photon beams, experimentalists put a great deal of efforts on extracting information on the EM properties of the ∆ isobar [1,2]. On the other hand, recent investigations in the lattice QCD produce more and more quantitative results on the structure of the baryon decuplet [3,4].…”

Section: Introductionmentioning

confidence: 99%