Probability Of Pair Production Research Articles

Theoretical estimate of the probability of pair production inαdecay

A theoretical estimate has been made of the probability of electron-positron pairs being produced in the $\ensuremath{\alpha}$ decay process. The results are in agreement with the experimental value observed in the decay of $^{241}\mathrm{Am}$, which is the only experimental result currently available. Estimates of the probabilities of pair production in other possible $\ensuremath{\alpha}$ decays are also given.[RADIOACTIVITY Calculation of internal pair formation in $\ensuremath{\alpha}$ decay.]

Correlation between the Stokes and anti-Stokes components in inelastic scattering of light

It is shown that the Stokes and anti-Stokes components, related by the conditions ωs+ωα = 2ωL and ks+kα=2kL, are correlated. When the temperature of the scattering material is high [kTh(ωL–ωs)] and/or stimulated scattering exists, this correlation assumes a classical form and is analogous to the Brown-Twiss intensity correlation. This intensity correlation is readily explained by modulation of the pump wave due to molecular vibrations so that the thermal fluctuations of energy of these vibrations are synchronously transferred into the s and α sidebands. At low temperatures and pump intensities (as well as outside Raman resonances) a photon correlation is found which is explained by the simultaneous production of pairs of s and α photons as a result of the spontaneous decay of two pump photons. The statistics of the scattering field in this case assumes a nonclassical form characterized by a relatively high (m1) probability of pair production compared with the product of the probabilities for the production of separate s and α photons (with the intensity correlation m≤1). An estimate of the rate of coincidences for the scattering of 1-W focused TEM00 pump radiation in liquid nitrogen yielded ~6 sec–1 and m~103. Analogs of the Kirchhoff equation were obtained for the inelastic scattering of light. These formulas, derived from the conditions of unitarity of the scattering process and equilibrium of matter, define the statistics of the scattered light in terms of the Raman gain and the parametric conversion coefficient.

Measurement of Bone Mineral Content Using Gamma-ray Attenuation by Pair Production

Abstract A new technique was developed for determining the mineral content of bone. The method is based on the pair production probability of high energy gamma-rays, particularly its dependence on the Z2/A ratio of the target material. Fifteen ox bone samples of irregular shapes were measured and a good correlation (r = 0.97) was displayed in the results compared with bone ash determinations. A statistical error of ±2% was obtained with a local radiation dose of 300 mrad.

Effective threshold energy for pair production in nonpolar semiconductors

A streaming model (high field) analysis is given for the average energy for and the probability of electron-hole pair production in a semiconductor when a quadratically energy dependent impact ionization cross-section exists above a threshold energy and competes with a nonpolar optical phonon scattering mechanism. A power series expansion method and tabulated results are provided to treat the resulting probability integrals of the form ∫ 0 ∞ x n exp {−( βx + x 3)}d x.

Evidence at the10−18probability level against the production of magnetic monopoles in proton interactions at 300 GeV/c

An electromagnetic search for magnetic monopoles that requires very few assumptions about their properties has been performed in material exposed to protons accelerated at Fermilab, to electrons at SLAC, and to $pp$ interactions at the CERN ISR. The most significant irradiation (Fermilab, 300 GeV/c) produced 2.5 \ifmmode\times\else\texttimes\fi{} ${10}^{18}$ primary proton-aluminum interactions. No monopoles were found. If monopoles exist with masses less than 12 GeV, the probability of pair production in a proton-nucleon collision is of the order of ${10}^{\ensuremath{-}18}$ or less with 95% confidence.

Pair production in an electric field applied for a short time

An expression is obtained for the probability of pair production in a homogeneous electric field applied for a short time and a constant inhomogeneous magnetic field when both fields have the same direction. The dependence of the probability is investigated for short and long times of application of the electric field.

Bremsstrahlung and Pair Production in Condensed Media at High Energies

The effect of multiple scattering on bremsstrahlung and pair production is considered. The probability of these processes decreases considerably at energies \ensuremath{\gtrsim}${10}^{13}$ ev.The calculations are carried out with the aid of the density matrix. The formulas thus obtained yield the probability of pair production and bremsstrahlung for arbitrary electron and photon energies.

Relative Cross Sections for Pair Production at 17.6 Mev

The relative cross sections for production of electron pairs by 17.6 Mev gamma-rays have been measured for Li, C, Al, Cu, Sn, and Pb. A gamma-ray pair spectrometer was used to count the number of pairs emitted from thin radiators of these materials when irradiated by 17.6 Mev gamma-rays produced in the ${\mathrm{Li}}^{7}(p,\ensuremath{\gamma}){\mathrm{Be}}^{8}$ reaction. For each material, the number of pairs counted per atom of radiator has been extrapolated to a radiator of zero thickness, in order to obtain the relative pair cross section. From these measurements some information can be obtained about the probability of pair production in the field of the atomic electrons, and about the errors in the theoretical pair cross sections of heavy elements, which presumably arise from the use of the Born approximation. It is found that the ratio of the pair cross section of an electron to that of a nucleus of unit charge is 0.8\ifmmode\pm\else\textpm\fi{}0.3. The data indicate that the pair cross sections of heavier elements are lower than predicted by the Born approximation, in qualitative agreement with measurements of the total absorption cross sections.

Points from Foregoing Letters

FROM measurements of the energy of an electron-positron pair, produced by a beta particle of energy 1·1 MV. in a mixture of nitrogen and mercury dimethyl vapour (5 per cent), Dr. F. C. Champion and A. Barber find that there is approximate agreement with the values obtained by Skobelzyn and Stepanowa when beta particles impinged on lead. It appears that the probability of pair production by beta particles of low energy increases rapidly with the atomic number and is large when the energy of the beta particle is of the order 2mc2.

Note on the Production of Pairs by Charged Particles

We compute the internal conversion by pair-production of the radiation emitted in the impact of charged particles. When the energy available for pair-production is large compared to $m{c}^{2}$, this simple method gives a valid estimate of pair-production by the impact. For electrons of very high energy the probability of pair-production increases as ${[\mathrm{ln} (\frac{E}{m{c}^{2}})]}^{2}$.