[General] background on pair production

[richgauthier at gmail.com]

Andrew and all,

  Here’s the reply I gave to someone at academia.edu <http://academia.edu/> who asked about Figure 3 diagraming e-p production from an incoming double-helix photon) in my article:

"The proposed superluminal energy quantum composing an electron or positron moves on each indicated moving mathematical (not physical) horn torus in Figure 3 in my article. The helical radius, wavelength and wave frequency f generating the horn torus of the quantum vortex electron is the same as the helical radius, wave length and wave frequency f  of the double-helix photon (and each single-helix half-photon) in the incoming photon. Green corresponds to the electron formed (with a reduction of the carried electric charge of each half-photon from -e sqrt(2/alpha) = -16.6e to -1 e) by the negatively-charged spin-1/2 half-photon from the incoming double-helix photon the while red corresponds to the positron. The angle of separation of the electron and positron trajectories depends on the energy of the incoming photon (smaller separation angle for greater incoming energy E=2 gamma mc^2) and the angles that the oppositely-moving created electron and positron make with the forward direction in the center-of-momentum system, where the incoming photon of energy E=2 gamma mc^2 and momentum p=2 gamma mc and the incoming atomic nucleus have equal and opposite momentum (but not equal and opposite energy). The atomic nucleus takes away a relatively high percentage of the momentum of the incoming photon (if the incoming photon energy is relatively low but greater than 1.022 MeV) during the formation of the e-p pair with the nucleus recoil, but takes away relatively very little of its energy, which (at low incoming photon energy) mostly goes into the created electron-positron pair. The atomic nucleus doesn't take away any of the spin of the incoming photon, which is conserved in the reaction where the spin 1 photon produces a spin 1/2 electron and a spin 1/2 positron.
   Your can read more about the experimental aspects and difficulty of measuring the threshold photon energy of e-p pair production in a very nice article at https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold <https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold> ."

     Richard

> On Jul 25, 2018, at 9:36 PM, Andrew Meulenberg <mules333 at gmail.com> wrote:
> 
> 
> Note that the threshold energy for pair production "...  given by the relation Eγ ≥ 2 mec (1 + me/mr), where mr is the mass of the recoiling particle," gives > 1 MeV for an electron or positron. My memory said that a >2 MeV photon was required. It may be related to the angle of recoiI. don't have time to look it up.
> 
> Andrew
> 
> On Tue, Jul 24, 2018 at 1:35 PM, Richard Gauthier <richgauthier at gmail.com <mailto:richgauthier at gmail.com>> wrote:
> Hi Chip and all,
>   Here's a little background on experimental pair production from the abstract to an article on Researchgate.net at https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold <https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold> 
>           Richard
> 
> 
> Pair production was first observed in 1932, which led to two early Nobel prizes in physics, to Carl Anderson for the discovery of positrons (1936) and to Paul Dirac for the theory of anti particles (1933). Science textbooks state that the production of electron-positron pairs is possible at photon energies above 1.022 MeV, which is the sum of the rest masses of the particles involved. Measurements at the threshold require a selectable photon energy in the range above 1 MeV, high-energy resolution to scan the onset, and high intensities. Due to the need of simultaneous energy and momentum conservation, pair production needs a recoiling particle, and thus it can be observed most easily in solid matter. More exactly, the minimum energy required for pair production is given by the relation Eγ ≥ 2 mec (1 + me/mr), where mr is the mass of the recoiling particle [1]. With the particle rest energy of me = 511 keV/c , in heavy atoms we get mr >> me, and thus in a good approximation photon energies Eγ ≥ 2·mec = 1.022 keV allow the creation of electron-positron pairs. However, for a proton as recoil particle the calculated threshold energy is increased by 557 eV, for a copper target by 9 eV, and even for the very heavy element 111Roentgenium by about 2.1 eV. Thus pair production cannot take place at exactly 2ámec. 
> 
> _______________________________________________
> If you no longer wish to receive communication from the Nature of Light and Particles General Discussion List at mules333 at gmail.com <mailto:mules333 at gmail.com>
> <a href="http://lists.natureoflightandparticles.org/options.cgi/general-natureoflightandparticles.org/mules333%40gmail.com?unsub=1&unsubconfirm=1 <http://lists.natureoflightandparticles.org/options.cgi/general-natureoflightandparticles.org/mules333%40gmail.com?unsub=1&unsubconfirm=1>">
> Click here to unsubscribe
> </a>
> 
> 
> _______________________________________________
> If you no longer wish to receive communication from the Nature of Light and Particles General Discussion List at richgauthier at gmail.com
> <a href="http://lists.natureoflightandparticles.org/options.cgi/general-natureoflightandparticles.org/richgauthier%40gmail.com?unsub=1&unsubconfirm=1">
> Click here to unsubscribe
> </a>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.natureoflightandparticles.org/pipermail/general-natureoflightandparticles.org/attachments/20180726/1da6af57/attachment.html>