Nucleon-nucleon bremsstrahlung at intermediate energies

Herrmann, Volker; Speth, J.; Nakayama, K.

doi:10.1103/physrevc.43.394

Cited by 58 publications

(72 citation statements)

References 31 publications

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“…While these reaction models were able to reproduce the qualitative features of experimental data, the quantitative agreement was normally within about a factor of 2. One of the major uncertainties is the input elementary pn → pnγ probability p γ which is still rather model dependent [582][583][584][585][586][587][588]. Early model studies usually could only describe within a factor of 2 the few existing data for the pn → pnγ process [538].…”

Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 99%

Recent progress and new challenges in isospin physics with heavy-ion reactions

2008

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The ultimate goal of studying isospin physics via heavy-ion reactions with neutron-rich, stable and/or radioactive nuclei is to explore the isospin dependence of in-medium nuclear effective interactions and the equation of state of neutron-rich nuclear matter, particularly the isospin-dependent term in the equation of state, i.e., the density dependence of the symmetry energy. Because of its great importance for understanding many phenomena in both nuclear physics and astrophysics, the study of the density dependence of the nuclear symmetry energy has been the main focus of the intermediate-energy heavy-ion physics community during the last decade, and significant progress has been achieved both experimentally and theoretically. In particular, a number of phenomena or observables have been identified as sensitive probes to the density dependence of the nuclear symmetry energy. Experimental studies have confirmed some of these interesting isospin-dependent effects and allowed us to constrain relatively stringently the symmetry energy at sub-saturation densities. The impacts of this constrained density dependence of the symmetry energy on the properties of neutron stars have also been studied, and they were found to be very useful for the astrophysical community. With new opportunities provided by the various radioactive beam facilities being constructed around the world, the study of isospin physics is expected to remain one of the forefront research areas in nuclear physics. In this report, we review the major progress achieved during the last decade in isospin physics with heavy ion reactions and discuss future challenges to the most important issues in this field.Key words: Equation of state of asymmetric nuclear matter, Nuclear symmetry energy, Heavy-ion reactions with neutron-rich nuclei, Neutron skin thickness of heavy nuclei, Neutron stars Constraining the Skyrme effective interactions and the neutron skin thickness of heavy nuclei using terrestrial nuclear laboratory data 216 8

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Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 99%

Recent progress and new challenges in isospin physics with heavy-ion reactions

2008

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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.…”

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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%

“…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.…”

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confidence: 99%

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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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“…The cross sections of the emitted photons have been measured for a long time (see Refs. [1][2][3][4][5][6][7][8][9][10][11]), and different theoretical models and approaches were developed to estimate the emitted photons (for example, see [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]). In particular, the spectra of the emitted photons are dependent on dynamics of the scattering of the proton off the nucleus, which is determined by interactions between the proton and nucleus.…”

Section: Introductionmentioning

confidence: 99%

New approach to determine proton-nucleus interactions from experimental bremsstrahlung data

Maydanyuk

Zhang

2015

Phys. Rev. C

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A new approach is presented to determine the proton-nucleus interactions from the analysis of the accompanying photon bremsstrahlung. We study the scattering of p + 208 Pb at the proton incident energies of 140 and 145 MeV, and the scattering of p + 12 C, p + 58 Ni, p + 107 Ag and p + 197 Au at the proton incident energy of 190 MeV. The model determines contributions of the coherent emission (formed by an interaction between the scattering proton and nucleus as a whole without the internal many-nucleon structure), incoherent emission (formed by interactions between the scattering proton and nucleus with the internal many-nucleon structure), and transition between them in dependence on the photon energy. The radius-parameter of the proton-nucleus potential for these reactions is extracted from the experimental bremsstrahlung data analysis. We explain the hump-shaped plateau in the intermediate-and high-energy regions of the spectra by the essential presence of the incoherent emission, while at low energies the coherent emission predominates which produces the logarithmic shape spectrum. We provide our predictions (in absolute scale) for the angular distribution of the bremsstrahlung photons in order to test our model, results and analysis in further experiments.

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Nucleon-nucleon bremsstrahlung at intermediate energies

Cited by 58 publications

References 31 publications

Recent progress and new challenges in isospin physics with heavy-ion reactions

Recent progress and new challenges in isospin physics with heavy-ion reactions

A relativistic meson-baryon description ofpp-Bremsstrahlung

New approach to determine proton-nucleus interactions from experimental bremsstrahlung data

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