The Positron

<p><strong>The Field Guide to Particle Physics : Season 3<br></strong><a href="https://pasayten.org/the-field-guide-to-particle-physics">https://pasayten.org/the-field-guide-to-particle-physics</a><br>©2022 The Pasayten Institute <a href="https://creativecommons.org/licenses/by-sa/4.0/">cc by-sa-4.0</a><br>The definitive resource for all data in particle physics is the Particle Data Group: <a href="https://pdg.lbl.gov/">https://pdg.lbl.gov</a>.</p><p>The Pasayten Institute is on a mission to build and share physics knowledge, without barriers! <a href="http://pasayten.org/heysean">Get in touch</a>.</p><p><a href="https://pasayten.org/the-field-guide-to-particle-physics/positron"><strong>The Positron</strong></a><strong></strong></p><p>The positron is the antiparticle partner to the electron.</p><p>Ostensibly, positrons have the same mass as the electron, around 511 keV.  They also have the same electric charge - at least up to a minus sign. The positron is of course positively charged.</p><p>Positrons also carry equal and opposite magnetic dipole moments to the electron: that little magnetic field carried often carried by elementary particles.</p><p>Like the electron, positrons are stable. They do not decay. But of course, we don’t see may of them around. When electrons and positrons collide, they annihilate each other! That is, they convert into a pair of photons, each with 511 keV of energy. </p><p>Because it is *extremely* rare for photons to interact with each other, this reaction almost never goes in reverse, which explains why positrons don’t accumulate here on Earth.</p><p>As you might be aware, the matter to antimatter ratio of our universe is way out of whack - which is great for us! - but makes it a little hard to study antimatter particles like the positron.</p><p><strong>Sources of Positrons</strong></p><p>Some positrons are produced by the decay of cosmogenic muons - or antimuons, more precisely - that are formed when the pi-plus - the positively charged pion  decays. Those pions are in turn