Re: Positrons

Liste des GroupesRevenir à sp relativity 
Sujet : Re: Positrons
De : AetherRegaind (at) *nospam* somewhere.in.the.aether (Aether Regained)
Groupes : sci.physics.relativity
Date : 08. Jul 2025, 20:50:00
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <104js6c$3o56g$1@tor.dont-email.me>
References : 1 2 3
Paul.B.Andersen:> Den 06.07.2025 06:27, skrev Bertietaylor:
>
In the case of cancer diagnosis a drug containing Fluorodeoxyglucose
is injected into the bloodstream of the patience.
>
Fluorodeoxyglucose contains F-18, which decay via β+ decay.
>
F-18 with 9 protons and 9 neutrons →
O-18 with 8 protons and 8 neutrons + positron + neutrino
>
When the ejected positron hits an electron somewhere in the body,
they annihilate and two gamma particles (photons) are created.
  e⁺ + e⁻  →  γ + γ
Energy and momentum are preserved.
The energy equivalence of an electron and a positron is 0.511 MeV,
so the energy of each of the gamma particles is 0.511 MeV. (0.024 Å)
(Mass is converted to pure kinetic energy of photons)
>
These gamma particles are detected by two detectors so a 3D image
is created.

I like to think that the e⁺ and  e⁻  don't actually annihilate, but
instead form a tight ball. Since this ball has no charge, it is for all
practical purposes undetectable. But then, the evidence that e⁺ and  e⁻
completely annihilate into 2 γ photons is compelling, since after all:

m_{e⁻}c^2 == 9.1094e-31 * 299792458^2 / 1.6022e-19 == 511 keV

A reasonable argument against this is that m_{e⁻} measurement is
controversial, and gamma ray detectors are calibrated assuming that the
e⁺ e⁻ annihilation radiation is 511 keV.

https://en.wikipedia.org/wiki/Annihilation_radiation
"
Because of their well-defined energy (511 keV) and characteristic,
Doppler-broadened shape, annihilation radiation can often be useful in
defining the energy calibration of a gamma ray spectrum.
"

https://upload.wikimedia.org/wikipedia/commons/7/78/Annihilation_Radiation.JPG

An independent measurement of the frequency/wavelength/wavenumber would
be more convincing, though I don't know how this can be done for
annihilation gamma radiation.


Date Sujet#  Auteur
6 Jul 25 * Re: Positrons23Bertietaylor
7 Jul 25 +* Re: Positrons16Paul.B.Andersen
7 Jul 25 i+- Re: Positrons1Athel Cornish-Bowden
7 Jul 25 i+- Re: Positrons1Maciej Woźniak
7 Jul 25 i+* Re: Positrons11Stefan Ram
8 Jul 25 ii`* Re: Positrons10Paul.B.Andersen
8 Jul 25 ii `* Re: Positrons9Stefan Ram
8 Jul 25 ii  `* Re: Positrons8Paul.B.Andersen
8 Jul 25 ii   `* Re: Positrons7Stefan Ram
8 Jul 25 ii    +* Re: Positrons2Stefan Ram
8 Jul 25 ii    i`- Re: Positrons1Stefan Ram
9 Jul 25 ii    `* Re: Positrons4Paul.B.Andersen
9 Jul 25 ii     `* Re: Positrons3Stefan Ram
9 Jul 25 ii      `* Re: Positrons2Stefan Ram
10 Jul 25 ii       `- Re: Positrons1Paul.B.Andersen
8 Jul 25 i`* Re: Positrons2Aether Regained
9 Jul 25 i `- Re: Positrons1Aether Regained
8 Jul 25 `* Re: Positrons6Aether Regained
8 Jul 25  +- Re: Positrons1William Hyde
9 Jul 25  +* Re: Positrons3Thomas Heger
9 Jul 25  i`* Re: Positrons2Aether Regained
10 Jul 25  i `- Re: Positrons1Thomas Heger
11 Jul 25  `- Re: Positrons1Bertietaylor

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