Positronium formation in low-energy positron–helium scattering

1996 ◽  
Vol 74 (7-8) ◽  
pp. 335-342 ◽  
Author(s):  
J. W. Humberston ◽  
P. Van Reeth
Keyword(s):  
Elastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Wave Functions ◽  
Positronium Formation ◽  
Recent Analysis ◽  
S Wave ◽  
Small Magnitude ◽  
Formation Cross Section ◽  
Positron Collisions

Detailed investigations were made of positron collisions with helium atoms in the Ore gap using a two-channel version of the Kohn variational method with very flexible trial wave functions and accurate correlated helium-target wave functions. Accurate values of the s-wave elastic scattering and positronium-formation cross sections are presented, together with preliminary values of the cross sections for s-wave scattering. The s-wave positronium-formation cross section in helium displays a remarkable similarity in both magnitude and energy dependence to the corresponding cross section in positron–hydrogen scattering, with a rapid rise from the positronium-formation threshold and a more gradual rise thereafter. Its small magnitude is consistent with the findings of a recent analysis of experimental measurements of the positronium-formation cross section. Calculations of the s-wave elastic-scattering cross section above and below the positronium-formation threshold reveal a Wigner "rounded step" at the threshold itself.

scholarly journals Positron?Lithium Inelastic Scattering with Polarisation Potentials

1991 ◽  
Vol 44 (6) ◽  
pp. 677 ◽  
Author(s):  
M EI-Shabshiry ◽  
SY EI Bakry ◽  
AH Moussa ◽  
MA Abdel-Raouf
Keyword(s):  
Inelastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Excitation Cross Section ◽  
Positronium Formation ◽  
Elastic Channel ◽  
Formation Cross Section ◽  
Positron Energy ◽  
Maximum Value

Positron-lithium inelastic scattering is studied at positron energies ranging from 0�005 to 20 eV using the coupled static model. Two channels are open namely the elastic and positronium formation. The polarisation potentials of the Li atom in the first channel and that of the positronium atom in the second channel are taken into consideration in calculating the corresponding cross sections. The partial cross sections in each channel are calculated for eight values of the total angular momentum (0 ~.e ~ 7). In the elastic channel the total cross section Ull has its maximum value at the lowest energy, and decreases with an increase in positron energy Ki. The total positronium formation cross section has a small dip at 0�1 eV, and maximum value at Ki = 1 �4 eV, and then decreases smoothly with e+ energy. We compare our results with those of Ward et al. (1989) where positronium formation is ignored. The agreement in elastic cross sections improves with e+ energy, while the total collisional cross sections have the closest agreement at 1�0 eV. From this comparison, we find that positronium formation is important in the very low energy region, and the role of the excitation cross section increases steadily with e+ energy.

MATTER-DENSITY DISTRIBUTION IN THREE-NUCLEON NUCLEI AND THEIR DIFFRACTIVE INTERACTION WITH HEAVY NUCLEI

2009 ◽  
Vol 18 (03) ◽  
pp. 665-674
Author(s):  
YU. A. BEREZHNOY ◽  
V. YU. KORDA ◽  
A. G. GAKH
Keyword(s):  
Experimental Data ◽  
Wave Function ◽  
Elastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Form Factors ◽  
Matter Density ◽  
Wave Functions ◽  
Heavy Nuclei ◽  
Nucleus Scattering

The nonrelativistic wave functions of 3 H and 3 He nuclei have been obtained on the basis of the experimentally measured charge form factors. The differential cross section of the elastic 3 He -nucleus scattering has been calculated with the help of the wave function derived. This cross section agrees with the experimental data on the elastic scattering of 3 He by 90 Zr , 120 Sn , and 208 Pb nuclei at 130 and 217 MeV. The integrated cross sections of various processes of 3 H and 3 He interaction with heavy nuclei have also been calculated.

Positronium formation in s-wave positron–hydrogen scattering

1982 ◽  
Vol 60 (4) ◽  
pp. 591-596 ◽  
Author(s):  
J. W. Humberston
Keyword(s):  
Cross Section ◽  
Atomic Hydrogen ◽  
Positronium Formation ◽  
Excitation Threshold ◽  
Matrix Elements ◽  
S Wave ◽  
Formation Cross Section ◽  
Positron Energy ◽  
R Matrix ◽  
A Value

A two channel version of the Kohn variational method is used with trial functions containing up to 120 linear variational parameters to calculate the R-matrix elements and the positronium formation cross section for the scattering of s-wave positrons by atomic hydrogen. Results are obtained in the energy range between the positronium formation threshold and the lowest excitation threshold of the atom. The positronium formation cross section rises very steeply to a value of [Formula: see text] just above the positronium formation threshold and then rises approximately linearly with positron energy to a value of [Formula: see text] just below the excitation threshold. Owing to the weakness of the coupling between the positron and positronium channels, the elastic scattering cross section for the positron continues smoothly across the positronium formation threshold.

Differential cross-section measurements in positron–argon collisions

1996 ◽  
Vol 74 (7-8) ◽  
pp. 505-508 ◽  
Author(s):  
R. M. Finch ◽  
Á. Kövér ◽  
M. Charlton ◽  
G. Laricchia
Keyword(s):  
Elastic Scattering ◽  
Differential Cross Section ◽  
Inelastic Scattering ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Coupling Effect ◽  
Channel Coupling ◽  
Scattering Cross

Differential cross sections for elastic scattering and ionization in positron–argon collisions as a function of energy (40–150 eV) are reported at 60°. Of particular interest is the energy range 55–60 eV, where earlier measurements by the Detroit group found a drop in the elastic-scattering cross section of a factor of 2. This structure has been tentatively attributed to a cross channel-coupling effect with an open inelastic-scattering channel, most likely ionization. Our results indicate that ionization remains an important channel over the same energy range and only begins to decrease at an energy above 60 eV.

The Scattering of Positrons by Helium: Total Cross Sections up to 270 eV

1975 ◽  
Vol 53 (10) ◽  
pp. 962-967 ◽  
Author(s):  
B. Jaduszliwer ◽  
A. Nakashima ◽  
D. A. L. Paul
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Reasonable Agreement ◽  
Experimental Results ◽  
Formation Cross Section ◽  
Sum Rule ◽  
Total Cross Sections ◽  
High Energies

The total cross sections for the scattering of positrons by helium have been measured by the method of transmission in the 16 to 270 eV energy range. The experimental results are higher than those of Canter et al. but are in reasonable agreement with recent results of Griffith et al., and at high energies tend towards Born approximation calculations. The integral of the cross section over positron momentum is smaller than the sum rule estimate made by Bransden et al. A tentative value of (0.034 ± 0.017)πa02 is assigned to the positronium formation cross section at threshold.

The 16O(p, γ)17F Direct Capture Cross Section with an Extrapolation to Astrophysical Energies

1975 ◽  
Vol 53 (17) ◽  
pp. 1672-1686 ◽  
Author(s):  
H. C. Chow ◽  
G. M. Griffiths ◽  
T. H. Hall
Keyword(s):  
Elastic Scattering ◽  
Excited States ◽  
Cross Section ◽  
Cross Sections ◽  
Capture Cross Section ◽  
Scattering Cross Section ◽  
Scattering Data ◽  
Capture Cross ◽  
Scattering Cross ◽  
Elastic Scattering Cross Section

The cross section for the direct radiative capture of protons by 16O has been measured relative to the proton elastic scattering cross section for energies from 800 to 2400 keV (CM). The elastic scattering cross section was normalized to the Rutherford scattering cross section at 385.5 keV. The capture cross section for the reaction 16O(p,γ)17F, which plays a role in hydrogen burning stars, has been extrapolated to stellar energies using a theoretical model which gives a good fit to the measured cross sections. The model involves calculation of electromagnetic matrix elements between initial and final state wave functions evaluated for Saxon–Woods potentials with parameters adjusted to fit both elastic scattering data and binding energies for the ground and first excited states of 17F. Cross sections for capture to the 5/2+ ground and 1/2+ first excited states of 17F in terms of astrophysical S factors valid for energies ≤ 100 keV have been found to be: S5/2+ = (0.317 + 0.0002E) keV b (± 8%); S1/2+ = (8.552 − 0.353E + 0.00013E2) keV b (± 5%).

s-wave positron-hydrogen scattering via Faddeev equations: Elastic scattering and positronium formation

1995 ◽  
Vol 51 (4) ◽  
pp. 2997-3004 ◽  
Author(s):  
Andrei A. Kvitsinsky ◽  
Jaume Carbonell ◽  
Claude Gignoux
Keyword(s):  
Elastic Scattering ◽  
Positronium Formation ◽  
S Wave ◽  
Faddeev Equations

Predictions of ρ meson cross-sections between AdS/QCD and boosted Gaussian wave functions in the color glass condensate model

2017 ◽  
Vol 32 (14) ◽  
pp. 1750081
Author(s):  
Jianquan Xie ◽  
Hui Peng
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Light Cone ◽  
Gaussian Model ◽  
Meson Production ◽  
Wave Functions ◽  
Dipole Model ◽  
Color Glass ◽  
Color Glass Condensate ◽  
Dipole Cross Section

Exclusive [Formula: see text] meson production is computed in dipole model using two different light-cone wave functions in this paper. The Color-Glass-Condensate (CGC) model is implemented to compute the dipole cross-section. The two light-cone wave functions are AdS/QCD model and boosted Gaussian model. It can be seen that the predictions using the two light-cone wave functions are close to each other.

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