[General] background on pair production
richgauthier at gmail.com
richgauthier at gmail.com
Sun Aug 12 22:33:37 PDT 2018
Hello all,
The following note is from Larry Reed at https://independent.academia.edu/LarryReed <https://independent.academia.edu/LarryReed>, copied with his permission, after he read my article on the quantum-vortex electron model. Comments are welcome. Please copy to Larry, Andre and Oreste also.
Richard
"Hi Richard
Thank you for the link to your recent paper. I am aware of some of your previous papers on the nature of the electron and applaud your work. Toroidal ring electron models appear much more plausible than other models previously proposed in the literature, e.g., points, strings, discs, spherical waves, etc which do not account for the observed physical properties or describe pair production/annihilation processes.
Believe the superluminal velocity equal to Weber's constant times the speed of light is correct as you have shown as this is inherent in a photon helicoid description. I do not quite understand the derivation for the relation given for charge Q = +/-16.6e. Toroidal models such as you have described may be extended to construct resonant spin models of the pion, muon, and tauon as in the Sternglass model. For example, the neutral pion may be represented as an orbiting electron/positron pair with aligned spins. A positively charged muon consists of an electron/positron central pair with opposite spins and an outer positron in a precessing frame orbiting in the same direction with positron spin aligned with that of the electron. A negative tauon is similar except that the outermost electron orbits retrograde to the central electron/positron pair. Perhaps you might wish to consider a paper on these composite structures using your electron model.
Best Regards,
Larry"
> On Jul 29, 2018, at 10:16 PM, André Michaud <srp2 at srpinc.org> wrote:
>
> Dear Chandra,
>
> I have no personal interpretation of these experiments carried out at SLAC.
>
> Apparently, the electron collision with the beam generated a gamma photon in excess of 1.022 MeV that then decoupled into an electron positron pair further away in the beam apparently due to interaction between this photon and other less energetic photons in the beam, after the initial electron had been deflected at an angle coherent with the recoil due to the process of emission of the high energy gamma photon.
>
> The process appears to have been successfully recorded a sufficient number of times to be accepted as significant to the peer-reviewers.
>
> The description in the related documentation is there for anyone to do his own study and interpretation.
>
> Given that all EM photons move at c, it seems mandatory that least one photon in excess of 1.022 MeV be present in the same highly focused volume of space with a sufficient concentration of other less energetic photons for the process to be possible. This seems to be what allows the process.
>
> I am satisfied with the interpretation made by the McDonald team.
>
> Best Regards
>
> André
> ---
> André Michaud
> "GSJournal admin" <ntham at gsjournal.net>
> http://www.gsjournal.net/
> https://orcid.org/0000-0003-2740-5684
> http://www.srpinc.org/
>
>
> On Mon, 30 Jul 2018 01:53:39 +0000, "Roychoudhuri, Chandra" wrote:
>
> Andre:
> The experiment you have cited starts with an electron. The intermediate Gamma is a conjecture of current particle theory. To me, this is not pure light beam-light beam scattering in pure vacuum.
> The world has several laser fusion labs. Enormous amount of laser energy is focussed into about 100 micron size D2/D3 pellet. Only time the labs record real particles output when the laser beams successfully hit the pellet. Whenever the focussed laser beams miss the pellet, no particles are generated.
> How come there is no photon-Photon interaction to generate particles?
> If my observation is backdated, kindly send me a recent reference.
> Chandra.
>
> Sent from my iPhone
>
> On Jul 29, 2018, at 2:58 PM, André Michaud <srp2 at srpinc.org <mailto:srp2 at srpinc.org>> wrote:
>
>>
>
> Dear Andrew,
>
> Just to mention that what seems not to have been covered in the pair production historical overview is pair production from photon-photon interaction in experiments carried out by McDonald et al. in 1997:
>
> http://www.slac.stanford.edu/exp/e144/ <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.researchgate.net%2Fderef%2Fhttp%253A%252F%252Fwww.slac.stanford.edu%252Fexp%252Fe144%252F&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368774034&sdata=FlWkFZa7z2%2FSaBoHykstrQ8cBHP4WSjcmFK6b19LGDU%3D&reserved=0>
> Best Regards
>
> André
> ---
>
>
> André Michaud
> "GSJournal admin" <ntham at gsjournal.net <mailto:ntham at gsjournal.net>>
> http://www.gsjournal.net/ <http://www.gsjournal.net/>
> https://orcid.org/0000-0003-2740-5684 <https://orcid.org/0000-0003-2740-5684>
> http://www.srpinc.org/ <http://www.srpinc.org/>
>
> On Sun, 29 Jul 2018 06:08:32 -0400, Andrew Meulenberg wrote:
>
> Dear Richard,
>
> Thank you for looking that up. The words you highlighted in the abstract are almost exactly like what I remember. I suspect that I read them in "The Atomic Nucleus" by Evans (1982), which was often a "Bible" for me in my work; but, I may have encountered the info earlier.
>
> The main point is that the curvature of the photon path during its "division" in passing by a charge can be quite different for the electron interaction compared with that from a nucleus. This puts some light (and limits) on the models for conversion of light to matter.
>
> Andrew
>
> On Sun, Jul 29, 2018 at 2:28 AM, <richgauthier at gmail.com <mailto:richgauthier at gmail.com>> wrote:
> Hello Andrew (and all),
> The below abstract from http://adsabs.harvard.edu/abs/2006RaPC...75..614H <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2006RaPC...75..614H&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368784038&sdata=ZhaaCuAlBx%2BD0QAVLexyQ8kO41MR%2FGmvb7QrpHQOsTQ%3D&reserved=0> supports your comment about pair production in photon-electron interactions.
> Richard
>
> Title: Electron positron pair production by photons: A historical overview
> Authors: Hubbell, J. H. <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fadsabs.harvard.edu%2Fcgi-bin%2Fauthor_form%3Fauthor%3DHubbell%2C%2BJ%26fullauthor%3DHubbell%2C%2520J.%2520H.%26charset%3DUTF-8%26db_key%3DPHY&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368784038&sdata=Ic9NsCEom2NNJBBy9Ysg7XQVAO45oVG%2F4jCB%2FKrysrA%3D&reserved=0>
> Affiliation: AA(National Institute of Standards and Technology, Mail Stop 8463, Gaithersburg, MD 20899-8463, USA.)
> Publication: Radiation Physics and Chemistry, Volume 75, Issue 6, p. 614-623.
> Publication Date: 06/2006
> Origin: ELSEVIER <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.elsevier.com%2F&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368794051&sdata=M98OE92Qya3E7RJECgcpIhUT7oNjmf6FbSbgrfr%2ByM0%3D&reserved=0>
> Abstract Copyright: (c) 2006 Elsevier Science B.V. All rights reserved.
> DOI: 10.1016/j.radphyschem.2005.10.008 <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoi.org%2F10.1016%2Fj.radphyschem.2005.10.008&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368794051&sdata=EMRxjvup2k1mzhFgHx6NW8VY%2BJCIyGtsehs%2BGjmFaG4%3D&reserved=0>
> Bibliographic Code: 2006RaPC...75..614H <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2006RaPC...75..614H&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368804059&sdata=20rE2Qa4XJnvMhyV4jzHv6ncDFnQ7fqsZYcAlihVjzU%3D&reserved=0>
> Abstract
>
> This account briefly traces the growth of our theoretical and experimental knowledge of electron-positron pair production by photons, from the prediction of the positron by Dirac [1928a. The quantum theory of the electron. Proc. R. Soc. (London) A 117, 610-624; 1928b. The quantum theory of the electron. Part II. Proc. R. Soc. (London) A 118, 1928b, 351-361] and subsequent cloud-chamber observations by Anderson [Energies of cosmic-ray particles. Phys. Rev. 43, 491-494], up to the present time. Photons of energies above 2 mec2 (1.022 MeV) can interact with the Coulomb field of an atomic nucleus to be transformed into an electron-positron pair, the probability increasing with increasing photon energy, up to a plateau at high energies, and increasing with increasing atomic number approximately as the square of the nuclear charge (proton number). This interaction can also take place in the field of an atomic electron, for photons of energy in excess of 4 mec2 (2.044 MeV), in which case the process is called triplet production due to the track of the recoiling atomic electron adding to the tracks of the created electron-positron pair. The last systematic computations and tabulations of pair and triplet cross sections, which are the predominant contributions to the photon mass attenuation coefficient for photon energies 10 MeV and higher, were those of Hubbell et al. [Pair, triplet, and total atomic cross sections (and mass attenuation coefficients) for 1 MeV-100 GeV photons in elements Z=1-100. J. Phys. Chem. Ref. Data 9, 1023-1147], from threshold (1.022 MeV) up to 100 GeV, for all elements Z=1-100. These computations required some ad hoc bridging functions between the available low-energy and high-energy theoretical models. Recently (1979-2001), Sud and collaborators have developed some new approaches including using distorted wave Born approximation (DWBA) theory to compute pair production cross sections in the intermediate energy region (5.0-10.0 MeV) on a firmer theoretical basis. These and other recent developments, and their possible implications for improved computations of pair and triplet cross sections, are discussed.
>
>
>>
>> On Jul 27, 2018, at 3:28 AM, Andrew Meulenberg <mules333 at gmail.com <mailto:mules333 at gmail.com>> wrote:
>>
>> Dear Richard,
>>
>> I realize that I might not have been clear enough in my statement about the scattering charge being a lepton rather than a proton or nucleus. And, my mistake in using the expression for Eγ certainly did not help the situation. You (and the reference) were focusing on the minimum energy threshold for pair production and the difficulties associated with the low production rates near the threshold. I was looking at the other end of the question where a light scattering center (e.g., an electron) makes energy and momentum conservation have a much greater effect.
>>
>> My memory of photon energy threshold >2 MeV for pair creation from a collision with an electron is consistent with Eγ ≥ 2 mec (1 + me/mr) = 4 mec = 2.044 MeV. This may only have been based on theoretical calculation. I'm not sure that there was any definitive experimental work to support it. However, the recoiling electron from this interaction would be energetic enough to give good confirming information. I'm not sure that Compton scattering would not interfere with the experiment.
>>
>> Andrew
>>
>>
>>
>>
>> On Thu, Jul 26, 2018 at 10:04 AM, <richgauthier at gmail.com <mailto:richgauthier at gmail.com>> wrote:
>> Hi Andrew and all,
>> Below is a pdf copy of the article https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.researchgate.net%2Fpublication%2F235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368804059&sdata=iVz71uH04xB8So0UO7004Le3X9To%2BXATlwlRkOVoggw%3D&reserved=0> with the abstract (below) you are quoting from. Definitely the minimum incoming photon energy is much less than 2 MeV and much nearer to the quoted value. It turns out that it’s very hard (as explained in the article) to experimentally confirm the minimum photon energy value for a particular recoil nuclear mass, given by the formula, so there’s surprisingly much experimental (and perhaps theoretical also) work still needed on this relatively straightforward conversion process of a photon to an electron-positron pair.
>> Richard
>>
>>
>>
>>
>>
>>>
>>> On Jul 25, 2018, at 9:36 PM, Andrew Meulenberg <mules333 at gmail.com <mailto: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. I 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 <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fresearchgate.net%2F&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368814063&sdata=j19qTH1qlbtqEx2KUXM1W728mOTtyEZgDNcaFLCLuGk%3D&reserved=0> at https://www.researchgate.net/publication/235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.researchgate.net%2Fpublication%2F235335367_The_Miracle_of_the_Electron-Positron_Pair_Production_Threshold&data=02%7C01%7Cchandra.roychoudhuri%40uconn.edu%7C969044c478e64c58fa8908d5f585541e%7C17f1a87e2a254eaab9df9d439034b080%7C0%7C0%7C636684875368824072&sdata=qj81KsSgsqtZbO3uWGwxjncHFKSQmBobqxxhiEbPWvA%3D&reserved=0>
>>> 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.
>>>
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