scholarly journals Scattering Cross Sections in Argon from Electron Transport Parameters

1982 ◽  
Vol 35 (1) ◽  
pp. 35 ◽  
Author(s):  
GN Haddad ◽  
TF O'Malley
Keyword(s):  
Phase Shift ◽  
Cross Section ◽  
Cross Sections ◽  
Lateral Diffusion ◽  
Phase Shifts ◽  
P Wave ◽  
Transport Parameters ◽  
S Wave ◽  
Wave Phase ◽  
Range Theory

Previously determined experimental drift velocities Vdr and ratios of lateral diffusion coefficient to mobility DT/µ have been refitted directly with a three parameter modified effective range theory (MER T) representation of the S wave phase shift, a one parameter fit to the P wave phase shift and fixed higher partial wave phase shifts. The MERT representation now extends to 1·0 eV, a threefold extension of the energy range of the MERT fit reported by Milloy et al. (1977). The total cross section derived from the phase shifts is also reported, together with the differential cross section at 1·0 eV which is compared with a previous experimental determination.

Positron–Helium Scattering Cross Sections and Phase Shifts below 19 eV

1973 ◽  
Vol 51 (14) ◽  
pp. 1565-1572 ◽  
Author(s):  
B. Jaduszliwer ◽  
D. A. L. Paul
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Phase Shifts ◽  
S Wave ◽  
Wave Phase ◽  
Entire Energy Range ◽  
Nice Agreement ◽  
Scattering Cross Sections ◽  
D Wave

The total cross sections for elastic scattering of positrons in the energy range from 4 to 19 eV have been measured by the method of transmission. By varying a magnetic field applied along the axis of the scattering chamber the transmitted fraction of the beam is altered, from which individual phase shifts can be extracted. s-, p-, and d-wave phase shifts are given over the entire energy range. The s-wave phase shifts are in agreement with values published by Drachman in 1968, while the p- and d-wave phase shifts are intermediate between values calculated by the same author in 1966 and 1971. The experimental results agree with those of Costello et al., and marginally with our own 1972 results, but are significantly different from those of Canter et al. We compute that the Ramsauer minimum in the diffusion cross section must be 0.04πa02 at 1.6 eV while the minimum in the total cross section is 0.11πa02 at 2.1 eV. The shoulder breadth observed in annihilation experiments is in nice agreement with what one would predict from our phase shifts.

Positron–Helium Scattering Cross Sections and Phase Shifts Below 19 eV: Addendum

1974 ◽  
Vol 52 (11) ◽  
pp. 1047-1049 ◽  
Author(s):  
B. Jaduszliwer ◽  
D. A. L. Paul
Keyword(s):  
Cross Sections ◽  
Cross Correlation ◽  
Phase Shifts ◽  
Phase Shift Analysis ◽  
P Wave ◽  
S Wave ◽  
Wave Phase ◽  
Shift Analysis ◽  
Scattering Cross Sections ◽  
Phase Phase

We have extended the phase shift analysis of our positron–helium transmission experiments to determine the importance of cross correlation between the s and p wave phase shifts in a previous paper. We have found out that using Humberston's s wave phase shifts with suitably modified p and d wave phase shifts leads to as good a fit to our experimental data as Drachman's s wave phase phase shifts. Preliminary values of total cross section are given in the 19 to 27 eV energy region.

FERMI PAIRING IN DILUTE 3He-HeII MIXTURES

2006 ◽  
Vol 20 (18) ◽  
pp. 2491-2504 ◽  
Author(s):  
M. K. AL-SUGHEIR ◽  
H. B. GHASSIB ◽  
B. R. JOUDEH
Keyword(s):  
Phase Shift ◽  
Crucial Role ◽  
Relative Phase ◽  
Phase Shifts ◽  
Fermi Momentum ◽  
Relative Momentum ◽  
Many Body ◽  
S Wave ◽  
Wave Phase ◽  
Zero Values

In this paper the Galitskii–Migdal–Feynman (GMF) formalism is applied to dilute 3He-HeII mixtures. In particular, the effect of the hole-hole scattering on pairing in these systems is investigated. To this end, the relative phase shifts incorporating many-body effects based on both Brueckner–Bethe–Goldstone (BBG) and GMF formalisms are calculated. In the GMF formalism, the S-wave phase shift at zero relative momentum is –π and has a cusp at the Fermi momentum; while in the BBG formalism, this phase shift has zero values up to the Fermi momentum. From these results we conclude that hole-hole scattering plays a crucial role in any possible fermion-fermion pairing in these systems.

Calculation of Average Collision Cross Sections of Low Energy for Elastic e-Ar Scattering Using MERT4

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
S. Hassanpour ◽  
S. Nguyen-Kuok
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Electron Scattering ◽  
Cross Sections ◽  
Phase Shifts ◽  
Low Energy ◽  
Effective Range ◽  
Collision Cross Sections ◽  
Range Theory ◽  
Effective Range Theory

Cross sections in the very low energy range are also represented by the modified effective-range theory (MERT) for low-energy electron scattering from the rare gas (argon). Simulations using published (theoretical) phase shifts indicate that extended versions of the standard effective-range theory with four adjustable parameters are required to give an adequate description of the phase shifts for argon. A four-parameter MERT fit gives a good representation of a recent electron–argon (e-Ar) total cross section experiment at energies less than 10.0 eV. Cross section Q(l) (E) for collision in dilute gases is given for any order l. Here Q(l) (E) are presented for l = 1. . .6. We present calculations for the elastic cross sections for electron scattering from argon. The improvement in the agreement between our theoretical calculations and the experimental measurements in the case of argon in scattering calculations are showed. Differential scattering experiments have been performed for the systems e-Ar in the energy range E = 0–10 eV and the angular range θ = 0–20° using a crossed-beam arrangement. Differential and integrated cross sections for the elastic scattering of low- and intermediate-energy (0–50 eV) electrons by argon atoms are calculated. For each impact energy, the phase shifts of the lower partial waves are obtained exactly by numerical integration of the radial equation. Transport coefficients of argon plasma are requested exactly, which is why we calculated the average collision cross sections for s = 1. . .11, l = 1. . .6.

scholarly journals Corrigendum: Mott?Schwinger Effect in the Elastic Scattering of Neutrons from 209Bi

1995 ◽  
Vol 48 (4) ◽  
pp. 737 ◽  
Author(s):  
N Alexander ◽  
K Amos ◽  
L Berge
Keyword(s):  
Partial Wave ◽  
Cross Section ◽  
Cross Sections ◽  
Phase Shifts ◽  
Exact Results ◽  
Forward Angle ◽  
Nuclear Scattering ◽  
Wave Phase ◽  
Angle Effect ◽  
Theoretical Developments

The results presented in our recent paper are in error. All of the theoretical developments contained therein are correct but the Mott-Schwinger (MS) interaction was doubly counted for small radii in our computations. That had a significant effect upon the exact values of the small-f partial wave phase shifts. In fact, the correct variation of the first 20 partial wave phase shifts from purely nuclear scattering are much smaller than we presented before. Consequently the variation caused by the MS effect in predictions of the observables is smaller than previously indicated, and particularly so for scattering angles in excess of 20� for the cases of neutrons scattered from bismuth that were considered. At small angles, there are still characteristic and noticeable differences caused by the MS interaction for the scattering of 0�5, 14�5 and 24 MeV neutrons from 209Bi. With the differential cross section, the forward angle effect remains as shown previously; that is, dominated by the cot (~O) element in the scattering amplitudes due to the infinite partial wave sum of MS phase contributions. But the deviations to the higher angle cross sections reported earlier are very much reduced. The major effects of the correction, however, are with the predictions of the spin-dependent measureables and the exact results for P(O) and the two general variables, Xvar(O) and Yvar(O).

scholarly journals The Interaction of Neutrons with 7Be at BBN Temperatures: Lack of Standard Nuclear Solution to the “Primordial 7Li Problem”

2020 ◽  
Vol 227 ◽  
pp. 01007 ◽  
Author(s):  
M. Gai ◽  
E.E. Kading ◽  
M. Hass ◽  
K.M. Nollett ◽  
S.R. Stern ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
High Energy ◽  
Big Bang ◽  
Alpha Particles ◽  
P Wave ◽  
Recent Measurement ◽  
S Wave ◽  
Big Bang Nucleosynthesis ◽  
The Cross

We report the first measurement of alpha-particles from the interaction of neutrons with 7Be at “temperatures” of Big Bang Nucleosynthesis (BBN). We measured the Maxwellian averaged cross sections (MACS), with neutron beams produced by the LiLiT at the SARAF in Israel (with kT = 49.5 keV hence 0.57 GK). In addition, we measured the cross section of the 7Be(n,p) reaction, which is in excellent agreement with the recent measurement of the n_TOF collaboration, further substantiating our method as a demonstration of “proof of principle”. The cross section for the 7Be(n,ga) and the 7Be(n,a) reaction measured in the “BBN window” is considerably smaller than compiled by Wagoner in 1969 and used today in Big Bang Nucleosynthesis (BBN). We also rule out a hitherto unknown resonance in 8Be at the BBN window, that was conjectured as a possible standard nuclear physics solution to the “Primordial 7Li Problem”. Together with previous results, we deduce a new Wagoner-like Rate for the destruction of 7Be by neutrons which is based on all current measured data. We conclude the lack of a standard nuclear solution to the “Primordial 7Li Problem”. Our upper limit on the cross sections for the high energy alpha-particles is in agreement with recent measurement of the n_TOF collaboration, but it is considerably smaller than the p-wave extrapolation of the Kyoto collaboration. We measured the alpha-particles from the 7Be(n,gi)8Be*(3.03 MeV) reaction, which is considerably larger than a previous s-wave estimate. Hence, in contrast, we conclude s-wave dominance at BBN energies, as would be expected due to the broad (122 keV) low lying 2” state at En = 10 keV.

KN s-wave phase shifts in the non-relativistic quark model

1995 ◽  
Vol 589 (4) ◽  
pp. 585-600 ◽  
Author(s):  
B. Silvestre-Brac ◽  
J. Leandri ◽  
J. Labarsouque
Keyword(s):  
Quark Model ◽  
Phase Shifts ◽  
Relativistic Quark Model ◽  
S Wave ◽  
Wave Phase

THE ANOMALOUS PROCESS γπ → ππ AND ITS IMPACT ON THE π0 TRANSITION FORM FACTOR

2014 ◽  
Vol 35 ◽  
pp. 1460397
Author(s):  
BASTIAN KUBIS
Keyword(s):  
Form Factor ◽  
Phase Shift ◽  
Theoretical Analysis ◽  
Cross Section ◽  
Transition Form Factor ◽  
P Wave ◽  
Chiral Anomaly ◽  
Transition Form ◽  
Dispersive Representation ◽  
Important Input

The process γπ → ππ, in the limit of vanishing photon and pion energies, is determined by the chiral anomaly. This reaction can be investigated experimentally using Primakoff reactions, as currently done at COMPASS. We derive a dispersive representation that allows one to extract the chiral anomaly from cross-section measurements up to 1 GeV, where effects of the ρ resonance are included model-independently via the ππ P-wave phase shift. We discuss how this amplitude serves as an important input to a dispersion-theoretical analysis of the π0 transition form factor, which in turn is a vital ingredient to the hadronic light-by-light contribution to the anomalous magnetic moment of the muon.

scholarly journals The scattering of alpha particles by helium

1959 ◽  
Vol 251 (1265) ◽  
pp. 143-155 ◽  
Keyword(s):  
Elastic Scattering ◽  
Phase Shift ◽  
Differential Cross Section ◽  
Excitation Energy ◽  
Cross Section ◽  
Differential Cross ◽  
Incident Energy ◽  
Phase Shifts ◽  
Alpha Particles

In order to obtain information about the levels of even spin and parity of 8 Be at energies above 11 MeV, the differential cross-section for the α-particle-helium elastic scattering has been measured at a series of beam energies from 23·1 to 38·4 MeV, for many c.m.s. angles between 30 and 90°. Phase shifts up to L = 8 have been calculated for each energy. Combining these results with previous figures for lower energies, the phase shifts δ 0 , δ 2 and δ 4 are thus known as functions of incident energy from 0·15 MeV to 38·4 MeV. The behaviour of the phase shift δ 4 confirms the existence of a previously suggested level with I = 4 at an excitation energy of about 11·4 MeV in 8 Be. The phase shifts δ 6 and δ 8 are small, as expected if the rotational series of levels in 8 Be term inates with I = 4.

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