Proton-proton bremsstrahlung calculations at 280 MeV

Brown, Virginia; Anthony, P. L.; Franklin, Jerrold

doi:10.1103/physrevc.44.1296

Cited by 32 publications

(32 citation statements)

References 17 publications

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“…In all modern proton-proton bremsstrahlung calculations [16,17,18,19,20] the electromagnetic part of the interaction is obtained by reducing the relativistic nucleon-nucleon-gamma vertex to obtain an effective 2 × 2 Hamiltonian which is used with two-component spinors in a nonrelativistic calculation. In some cases, e. g. ref.…”

Section: (T) and Hmentioning

confidence: 99%

“…For example, in electron scattering from nuclei, one evaluates matrix elements of electromagnetic operators ("semi-de-relativized" according to the direct Pauli reduction procedure) between nonrelativistic solutions of the Schrödinger equation with a given NN potential [9,10,11,12,13], but there also exist treatments that make use of the Foldy-Wouthuysen procedure to obtain semi-relativistic op-erators [8,14,15]. Similarly, in proton-proton bremsstrahlung the strong interaction part is conventionally treated using a nonrelativistic LippmannSchwinger approach, whereas for the electromagnetic interaction a semirelativistic ansatz, involving either the Foldy-Wouthuysen method or the direct Pauli reduction method is made [16,17,18,19,20].…”

Section: Introductionmentioning

confidence: 99%

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Effective hamiltonians with relativistic corrections: The Foldy-Wouthuysen transformation versus the direct Pauli reduction

1994

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Section: (T) and Hmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effective hamiltonians with relativistic corrections: The Foldy-Wouthuysen transformation versus the direct Pauli reduction

1994

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“…2a (2) shows that the isovector exchange currents are large near θ 3 = θ 4 ∼ 20 • . We realize that recommendations [7,10] based nucleon-pole dominance with maximum photon energies call for increased emphasis on the extreme forward-angle geometries. Although these geometries succeed in maximizing the differences between the potential-model calculations, Figs.…”

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confidence: 99%

Sensitivity of pp-bremsstrahlung to meson-exchange currents

Eden

Gari

1995

Physics Letters B

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We present pp-bremsstrahlung cross section calculations at the π-production threshold to search for kinematics that best differentiate model-dependent descriptions of the NN t-matrix and accentuate the contributions of isoscalar meson-exchange currents. Existing optimization procedures are shown to be completely unreliable due to the neglect of meson-exchange currents and phase space variations. We show that phase-space hides the most important differences in model t-matrices, but that improved data will be critical to further investigations of exchange currents.

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“…In a more approximate scheme, it may take the form [6] of a direct Pauli reduction. These two approaches lead to differences of order 7% in the (p, pT) cross section at 280 MeV [10], and differ from the results that are obtained with a completely non-relativistic current density [3,5] by as much as 15% [-2, 6]. The corresponding differences in the spin-observables are generally even larger.…”

mentioning

confidence: 94%

“…1, and emphasis has been placed on improving a number of approximations used to calculate these contributions alone. For example, in some calculations the relativistic spin corrections [2,4] have been retained, and in others [3,5] the rcscatter contributions ( Fig. lc) have been calculated without recourse to the soft-photon approximation.…”

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confidence: 99%

A relativistic meson-baryon description ofpp-Bremsstrahlung

Eden

Plümper

Gari

et al. 1993

Z. Physik A - Hadrons and Nuclei

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Abstract. We describe a relativistic approach to the calculation of nucleon-nucleon Bremsstrahlung, where all meson-baryon and meson-baryon-photon interactions can be calculated consistently and microscopically. In this first relativistic approach to the problem, we present numerical results including both single-scatter and rescatter contributions with a relativistic current density, within a model where the explicit photon coupling to meson-exchange currents are small. The need for high precision (p, PY) measurements is stressed. PACS: 13.75.Cs; 25.10.+s; 27.30.+y The consistent microscopic prediction of (p, PT) observables requires the calculation of the photon coupling to an interacting meson-baryon system. For processes where the photon couples to a free nucleon before or after strong-interactions, one can express the (P, PT) invariant amplitude in the two-potential formalism of GellMann and Goldberger [1], consisting of a one-body nuclear current density and an off-shell NN T-matrix. The essential advantage of this approach is that the NN Tmatrix is defined to all orders in the strong-interaction coupling constant. All recent (p, p 7) calculations use this two-potential formalism, and obtain the NN T-matrices from the Lippmann-Schwinger [24] or BlankenbeclerSugar [5,6] equations for a non-relativistic boson-exchange potential such as Bonn [7] or Paris [8], or from inverse-scattering methods [9], and therefore include only the positive frequency components of the two-nucleon wavefunctions. Under this restriction, only the positive frequency processes that are shown in Fig. 1 are included.In all existing (p, P7) calculations, where the non-relativistic strong-interaction models neglect the negativefrequency components of the off-shell nulceons, it is necThis work is supported by COSY-KFA Jfilich (41140512) and Deutsche Forschungsgemeinschaft (Ga 153/11-4) essary to apply some kind of non-relativistic reduction to the current operator. This may take the form [2, 41 of a Foldy Wouthuysen transformation to obtain a nonrelativistic current with 'relativistic' spin corrections, which are retained to some approximate order, according to where the infinite p/m-expansion is truncated. In a more approximate scheme, it may take the form [6] of a direct Pauli reduction. These two approaches lead to differences of order 7% in the (p, pT) cross section at 280 MeV [10], and differ from the results that are obtained with a completely non-relativistic current density [3,5] by as much as 15% [-2, 6]. The corresponding differences in the spin-observables are generally even larger.This suggests the need for relativistic wave functions in (p, PT) calculations, so that the relativistic current density can be calculated without recourse to any (p/m)_ expansion, and the off-shell two-nucleon state can be properly described as including both its the positive and negative frequency contributions, as shown in Fig. 1. In the Feynman-Stfikelberg interpretation, the negative frequency contributions represent NN creation and annihilat...

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Proton-proton bremsstrahlung calculations at 280 MeV

Cited by 32 publications

References 17 publications

Effective hamiltonians with relativistic corrections: The Foldy-Wouthuysen transformation versus the direct Pauli reduction

Effective hamiltonians with relativistic corrections: The Foldy-Wouthuysen transformation versus the direct Pauli reduction

Sensitivity of pp-bremsstrahlung to meson-exchange currents

A relativistic meson-baryon description ofpp-Bremsstrahlung

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