Complete set of total cross sections for imaginary parts ofndforward scattering amplitudes, and three-nucleon force effects

Recent measurements of resonances in slow neutron total cross sections yield good estimates of the average level spacing, D, in medium and heavy nuclei. These spacings show large variations, by factors of 103 to 105, in the region of magic numbers of nucleons. There are also variations by smaller factors between nuclei with even and odd numbers of protons or neutrons. The even–odd effect is a co-operative phenomenon; it can be approximately treated by redefining the ground state to be used for a Fermi gas model. After this correction the gas model should predict D with reasonable accuracy since it is required only to define the density of a complete set of states. The magic number variations are shown to be fitted by an improved approximation to the single-nucleon level density. This is obtained from the observed sequence of single-particle spins and the assumption that the energy interval between spin subshells is constant. Fifty-two observed spacings are fitted by a two-parameter formula with an average uncertainty factor 3. Many of the larger remaining differences between observation and the predictions of the model are qualitatively explicable as expected departures from this uniform spacing hypothesis.

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PARITY AND TIME REVERSAL VIOLATION IN RESONANCE NEUTRON TOTAL CROSS SECTIONS WITH POLARIZED TARGETS

International Journal of Modern Physics A ◽

10.1142/s0217751x90001008 ◽

1990 ◽

Vol 05 (11) ◽

pp. 2181-2194 ◽

Cited By ~ 28

Author(s):

C. R. GOULD ◽

D. G. HAASE ◽

N. R. ROBERSON ◽

H. POSTMA ◽

J. D. BOWMAN

Keyword(s):

Cross Sections ◽

Time Reversal ◽

Analytic Form ◽

Spin Representation ◽

Resonance Neutron ◽

Total Cross Sections ◽

Polarized Target ◽

Complete Set ◽

Closed Analytic Form ◽

Polarized Targets

The formalism for evaluating parity and time reversal violating terms in total cross sections of polarized targets and low energy resonance neutrons is reviewed. A complete set of symmetry violating terms (P-odd, T-even; P-odd, T-odd; and P-even, T-odd) is obtained by analyzing the dependence of the cross section on the statistical tensors describing the beam and target. Results are tabulated in numerical and closed analytic form, using the j-spin representation. P-odd, T-even experiments are classified, with emphasis on experiments with an unpolarized beam and a polarized target where the effect of induced polarization is found to be small. Different combinations of partial neutron widths are shown to enter when P-odd, T-odd effects are compared to P-odd, T-even effects. The results for P-even, T-odd experiments for single level and two level mixing are summarized.

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Neutron Total Cross-Sections at 18.8 eV

Zeitschrift für Naturforschung A ◽

10.1515/zna-1974-1207 ◽

1974 ◽

Vol 29 (12) ◽

pp. 1750-1753 ◽

Cited By ~ 3

Author(s):

W. Dilg

Keyword(s):

Experimental Data ◽

Scattering Amplitudes ◽

Neutron Scattering ◽

Neutron Energy ◽

Cross Sections ◽

Total Cross Sections ◽

Neutron Transmission ◽

Spin Dependent Scattering ◽

Transmission Measurements ◽

Scattering Cross Sections

Neutron transmission measurements were performed at 18.8 eV neutron energy on F, Al, Sc, V, Fe, Co, Cu, Zn and Nb, in order to acurately determine the "free" scattering cross-sections of these elements. Coherent neutron scattering amplitudes are derived for F, AI, Sc, Fe, Cu, Zn and Nb, using available experimental data of the isotopic and spin-incoherent cross-sections. Spin-dependent scattering amplitudes a(l+½) and a(l-½) are evaluated for the monoisotopes F, Al, Sc, V, Co and Nb.

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Analysis of STEM micrographs of thick objects

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081395 ◽

1978 ◽

Vol 36 (2) ◽

pp. 106-107

Author(s):

S. Golladay

Keyword(s):

Inelastic Scattering ◽

Multiple Scattering ◽

Mass Distribution ◽

Cross Sections ◽

Phase Contrast ◽

Image Point ◽

Contrast Effects ◽

Total Cross Sections ◽

Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

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Production Cross Sections of Fragments from Beams of 400–650 MeV per Nucleon9Be,11B,12C,14N,15N,16O,20Ne,22Ne,56Fe, and58Ni Nuclei Interacting in a Liquid Hydrogen Target. I. Charge Changing and Total Cross Sections

The Astrophysical Journal ◽

10.1086/306445 ◽

1998 ◽

Vol 508 (2) ◽

pp. 940-948 ◽

Cited By ~ 34

Author(s):

W. R. Webber ◽

J. C. Kish ◽

J. M. Rockstroh ◽

Y. Cassagnou ◽

R. Legrain ◽

...

Keyword(s):

Cross Sections ◽

Production Cross ◽

Liquid Hydrogen ◽

Liquid Hydrogen Target ◽

Hydrogen Target ◽

Total Cross Sections

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Total cross sections of eγ → $$ eX\overline{X} $$ processes with X = μ, γ, e via multiloop methods

Journal of High Energy Physics ◽

10.1007/jhep01(2021)144 ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Roman N. Lee ◽

Alexey A. Lyubyakin ◽

Vyacheslav A. Stotsky

Keyword(s):

Cross Section ◽

Cross Sections ◽

Elliptic Integral ◽

High Energy ◽

Calculation Methods ◽

Complete Elliptic Integral ◽

Total Cross Sections ◽

Multiloop Calculation ◽

The Cross ◽

Analytical Expressions

Abstract Using modern multiloop calculation methods, we derive the analytical expressions for the total cross sections of the processes e−γ →$$ {e}^{-}X\overline{X} $$ e − X X ¯ with X = μ, γ or e at arbitrary energies. For the first two processes our results are expressed via classical polylogarithms. The cross section of e−γ → e−e−e+ is represented as a one-fold integral of complete elliptic integral K and logarithms. Using our results, we calculate the threshold and high-energy asymptotics and compare them with available results.

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