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

1990 ◽  
Vol 05 (11) ◽  
pp. 2181-2194 ◽  
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.

SHELL EFFECTS ON THE SPACING OF NUCLEAR LEVELS

1956 ◽  
Vol 34 (8) ◽  
pp. 804-829 ◽  
Author(s):  
T. D. Newton
Keyword(s):  
Cross Sections ◽  
Level Density ◽  
Magic Number ◽  
Slow Neutron ◽  
Magic Numbers ◽  
Heavy Nuclei ◽  
Total Cross Sections ◽  
Shell Effects ◽  
Complete Set ◽  
Nuclear Levels

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.

scholarly journals The H and D Polarized Target for Spin–Filtering Measurements at COSY

2016 ◽  
Vol 40 ◽  
pp. 1660149
Author(s):  
Giuseppe Ciullo ◽  
Marco Statera ◽  
Paolo Lenisa ◽  
Alexander Nass ◽  
Giuseppe Tagliente
Keyword(s):  
Cross Section ◽  
Time Reversal ◽  
Testing Time ◽  
Time Reversal Invariance ◽  
Polarized Target ◽  
Reversal Invariance ◽  
Polarized Targets ◽  
Main Frame ◽  
Spin Filtering

In the main frame of the PAX (Polarized Antiproton eXperiments) collaboration, which engaged the challenging purpose of polarizing antiproton beams, the possibility to have H or D polarized targets requires a daily switchable source and its diagnostics: mainly change is a dual cavity tunable for H and D. The commissioning of PAX has been fullfilled, for the transverse case, on the COSY (COoler SYnchrotron) proton ring, achieving milestones on spin–dependent cross–section measurements. Now the longitudinal case could provide sensitive polarization results. An H or D source allows the exploration of the spin–filtering process with a deuterium polarized target, and opens new chances for testing Time Reversal Invariance at COSY (TRIC).

Analysis of STEM micrographs of thick objects

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.

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

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.

Positronium- and positron–H2O total cross sections

2006 ◽  
Vol 39 (6) ◽  
pp. 1337-1344 ◽  
Author(s):  
J Beale ◽  
S Armitage ◽  
G Laricchia
Keyword(s):  
Cross Sections ◽  
Total Cross Sections
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