Measurement of the LT-asymmetry in πelectroproduction at the energy of the Δ(1232)-resonance

Elsner, D.; Süle, A.; Barneo, P.; Bartsch, P.; Baumann, D.; Bermuth, J.; Böhm, R.; Bosnar, D.; Ding, M.; Distler, M. O.; Drechsel, D.; Ewald, I.; Friedrich, J.; Grözinger, S.; Jennewein, P.; Kamalov, S.S.; Klein, F.; Köhl, M.; Krygier, K. W.; Merkel, H.; Merle, P.; Müller, U.; Neuhausen, R.; Pospischil, Th.; Potokar, M.; Rosner, G.; Schmieden, H.; Seimetz, M.; Strähle, O.; Tiator, L.; Walcher, Th.; Weis, M.

doi:10.1140/epja/i2005-10212-2

Cited by 51 publications

(64 citation statements)

References 36 publications

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“…An implication of these principles is dispersionlike expansions of the FFs F f (Q 2 ), the simplest version being given by the VMD model (10). To fit the experimental data [6,7,8,9,40,10,11,12,13,14,15], we adjust the parameters of the logarithmic functions L f (Q 2 ) and the meson-baryon couplings κ k f (0) for the meson spectrum of the PDG review [8]. The ratios of the FFs given by the VMD model (10) are restricted so as not to deviate from the quasi-scaling limit by more than 0.1% at Q 2 0.5 GeV 2 .…”

Section: Data Analysis and The Quasi-scalingmentioning

confidence: 99%

Low-Q2 scaling behavior of the form-factor ratios for the NΔ(1232)-transition

Vereshkov

Volchanskiy

2010

Physics Letters B

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We address the issue of the scaling behavior of the nucleon electromagnetic form factors (FFs). We propose a consistent Lagrangian of the electromagnetic N∆ (1232)-interaction possessing all the internal symmetries of the spin-3 2 baryon resonance, point and gauge invariance. The point and gauge invariant FFs may exhibit quasi-scaling behavior-while the FFs do not reach asymptotic scaling domain, the ratios thereof do. The hypothesis of the quasi-scaling is in good agreement with the experimental data available at Q 2 0.4 GeV 2 .

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Section: Data Analysis and The Quasi-scalingmentioning

confidence: 99%

Low-Q2 scaling behavior of the form-factor ratios for the NΔ(1232)-transition

Vereshkov

Volchanskiy

2010

Physics Letters B

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“…(60). The blue circles are data points from MAMI for R EM [1], and R SM [40,41]. The green squares are data points from BATES [3].…”

Section: Appendix B: Absorptive Parts Of the Vertex Correctionsmentioning

confidence: 99%

Chiral effective-field theory in theΔ(1232)region: Pion electroproduction on the nucleon

2006

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We develop an extension of chiral perturbation theory to the ∆(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon (e − N → e − N π). We present a complete calculation of this process, in the ∆-resonance region, up to next-to-leading order in the δ-expansion. At this order, the only free parameters are the three low-energy constants corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) γN → ∆ transition strength. After fitting these parameters to a few well-known data, our calculation provides a prediction for observables and multipole amplitudes of pion electroproduction. These results compare favorably with the phenomenological multipole solutions and recent experimental results from MIT-Bates and MAMI. Our prediction for the pion-mass dependence of the γN ∆ form factors offers an explanation for the discrepancy between the recent lattice-QCD results and the experimental value for the "C2/M1 ratio" at low Q 2 .

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“…The solid curves are the MAID2005 solutions. The experimental analyses are from: MAMI(solid star [9], open circles [29], open diamond [15], solid diamond [32]), Bates(open squares [16]), ELSA(solid squares [17]), JLab(open triangles [26], solid triangles [28]). The solid circles and asterisks show our own analysis to the JLab Hall C data [20] and JLab Hall A data [27], respectively.…”

Section: The Nucleon To Delta(1232) Transitionmentioning

confidence: 99%

“…However, this preliminary result is only a fit of the single-Q2 points and not yet a fit to the measured cross sections. In a recent paper of Elsner et al [32] we have analyzed the longitudinal-transverse asymmetries LT and LT ′ measured at Mainz in two different experiments at W = 1232 MeV and Q 2 = 0.2 GeV 2 . These asymmetries are related to the partial cross sections via…”

Section: The Nucleon To Delta(1232) Transitionmentioning

confidence: 99%

“…However, all these parameters are practically fixed, therefore we have allowed for an additional variation of a real and imaginary non-Born part in the S 0+ multipole. Using the new ρ LT data of Elsner [32] in conjunction with the previous measurement of the ρ LT ′ asymmetry of Bartsch et al [36], we performed a re-fit of the MAID2003 parameters. We obtained sensitivity to real and imaginary parts of the S 1+ and S 0+ amplitudes in the pπ 0 channel.…”

Section: The Nucleon To Delta(1232) Transitionmentioning

confidence: 99%

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Nucleon Resonance Excitation with Virtual Photons

Tiator¹,

Kamalov²

2007

AIP Conference Proceedings

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Abstract. The unitary isobar model MAID is used for a partial wave analysis of pion photoproduction and electroproduction data on the nucleon. In particular we have taken emphasis on the region of the ∆(1232) resonance and have separated the resonance and background amplitudes with the K-matrix approach. This leads to electromagnetic properties of the dressed ∆ resonance, where all multipole amplitudes become purely imaginary and all form factors and helicity amplitudes become purely real at the K-matrix pole of W = M ∆ = 1232 MeV. The R EM = E2/M1 and R SM = C2/M1 ratios of the quadrupole excitation are compared to recent data analysis of different groups. The R EM ratio of MAID2005 agrees very well with the data and has a linear behavior over the whole experimentally explored Q 2 region with a small positive slope that predicts a zero crossing around 3.5 GeV 2 . The recent R SM data for Q 2 < 0.2 GeV 2 indicate a qualitative change in the shape of the ratio which can be explained by the impact of the Siegert theorem at pseudothreshold (Q 2 = −0.086GeV 2 ) in the unphysical region.

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Measurement of the LT-asymmetry in πelectroproduction at the energy of the Δ(1232)-resonance

Cited by 51 publications

References 36 publications

Low-Q2 scaling behavior of the form-factor ratios for the NΔ(1232)-transition

Low-Q2 scaling behavior of the form-factor ratios for the NΔ(1232)-transition

Chiral effective-field theory in theΔ(1232)region: Pion electroproduction on the nucleon

Nucleon Resonance Excitation with Virtual Photons

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