Dynamical model for π-photoproduction in the Δ-channel

Cenni, R.; Dillon, G.; Christillin, P.

doi:10.1007/bf02733834

Cited by 17 publications

(7 citation statements)

References 20 publications

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“…A third approach uses a model to calculate the background amplitude, then determines the resonance contribution by fitting the empirical E,+( -', ) amplitude. The results for the bare b, amplitude are -(3.1+1.3)% for the model presented here [11], -(1.5+0.72)% [13], -4% [18], 0% [9], and +4% [12] (Tanabe and Ohta). The results for the dressed b, amplitude are -2.2%%uo for the model presented here [11].…”

Section: Qualitatively the Shape Of Ei+ ( -' ) [Figs 2(c) And 2(d)]mentioning

confidence: 50%

Quadrupole amplitude in the γN⇆Δ transition

1993

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The tensor part of the color hyperfine interaction between quarks leads to a small electric quadrupole amplitude in the yN~A excitation. It is demonstrated that pion photoproduction data available previously have a low sensitivity to the (isospin 2) electric quadrupole amplitude, E~+( z ). An additional difficulty is that there is an appreciable background contribution to the total El+ amplitude. The consequent difficulties in extracting the resonant part of this small amplitude from experiment are discussed.It is shown that yp~~p and yp~~+ n cross sections near 0' and 180', and also those near 90' with polarized y rays, both with and without polarized targets, have the greatest sensitivity to the El+ ( -, ) amplitude. Since the anticipated observable effects of the resonant E2 amplitude are expected to be -10% to 20% in magnitude, the required accuracy to extract a precise E2/M1 ratio is -l%%uo for both experiment and theory.PACS number(s): 13.60.Rj, 14.20.Gk

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Section: Qualitatively the Shape Of Ei+ ( -' ) [Figs 2(c) And 2(d)]mentioning

confidence: 50%

Quadrupole amplitude in the γN⇆Δ transition

1993

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“…Finally let us discuss the coupling constants. We put as usual f 2 πN N /4π = 0.08 and f 2 πN ∆ /4π = 0.32; the value we use for f πN ∆ is commonly employed in the literature, somehow higher than the value obtained by the N -N phase shift analysis carried out in constructing the Bonn potential, but lower than the results of a recent fit [48]. It is remarkable that the precise value of this parameter depends on the details of the underlying dynamical model: within the Bonn potential approach, in our opinion, is necessary to underestimate the πN ∆ coupling, to effectively account for the ∆-∆ repulsion inside a box diagram [49,50].…”

Section: The Dynamical Modelmentioning

confidence: 99%

“…Diagrams f) to k) have the same structure of eqs. (48) and (49),but the proper expressions for the various Π (3) functions must be used [34], according to which line in the diagram pertains to a nucleon or to a ∆. The last step before the numerical evaluation of the integrals is the calculation of the spin-isospin traces.…”

Section: Evaluation Of the Diagramsmentioning

confidence: 99%

Functional approach to the electromagnetic response function: The longitudinal channel

Cenni¹,

Saracco²

1994

Phys. Rev. C

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In this paper we address the (charge) longitudinal electromagnetic response for a homogeneous system of nucleons interacting via meson exchanges in the functional framework. This approach warrants consistency if the calculation is carried on order-by-order in the mesonic loop expansion with RPA-dressed mesonic propagators. At the 1-loop order and considering π, ρ and ω exchanges we obtain a quenching of the response, in line with the experimental results. 21.65

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“…This interaction is different (due to different parametrisation) in the models A and B but small in both the cases. As has been shown in [12], all principal value integrals in this case…”

Section: The Electromagnetic Constants Of the A-isobarmentioning

confidence: 58%

“…The results of our analysis in the case of models A and B of [ 11 ] are rather similar. This indicates, to our mind, the validity of the procedure which has been proposed in [12] for the construction of the n-photoproduction amplitude in the P33-channel.…”

Section: Qkmentioning

confidence: 81%

Off-shell effects in the dynamical model of pion photoproduction

Chumbalov

Kamalov

1992

Z. Physik A - Hadrons and Nuclei

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In terms of the dynamical model the rescattering effects for the Eo+, MI+ and El+ multipoles are analyzed. Strong correlation between the sensitivity to the off-shell behaviour of the T~u-matrix and the representation of the pion propagator in the photoproduction operator is shown to exist. For the time-ordered choice of a pion propagator the effect of a final state interaction is determined by the charge-exchange channel. In this case the off-shell effects are not important. It is also shown that the value of the coupling constant of the E2-transition in the 7NA-vertex depends on a version of the separable model for the ~N-interaction in the P33-channel. PACS: 25.20.Lj

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Dynamical model for π-photoproduction in the Δ-channel

Cited by 17 publications

References 20 publications

Quadrupole amplitude in the γN⇆Δ transition

Quadrupole amplitude in the γN⇆Δ transition

Functional approach to the electromagnetic response function: The longitudinal channel

Off-shell effects in the dynamical model of pion photoproduction

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