What is a positron?

Answer 1

A positron is a positively charged electron. It's an antielectron - antimatter! The positron has a charge of +1 (just the opposite of the -1 of the electron), and a spin of 1/2 as an electron does. The mass of this elementary particle is about 9.103826 x 10-31 kg. The actual charge on this particle is about +1.602 x 10-19 coulombs. We write it as β+ or e+ in nuclear equations.

It was Paul Dirac who first theorized that it may exist back in 1928, and in 1932, Carl D. Anderson discovered and named the positron. How was it done? By allowing cosmic rays to pass through a cloud chamber shielded with lead and set up in a magnetic field, the electron-positron pairs that were sometimes created could be observed. Once created, the particles moved (curved) in opposite directions within the magnetic field. Simple and clever! It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it.

We should also note that the positron is emitted (positron emission) in beta plus decay, which is a form of radioactive decay. Pair production, the "conversion" of electromagnetic energy into a positron and an electron, is also a source of positrons. Regardless of the source, the positron will always seek to "combine" with any nearby electron with the mass of both particles being converted into electromagnetic energy (a pair of gamma rays). A more detailed description and some of the other characteristics of the positron can be found in the Wikipedia article on that subject. A link is provided below to that post and also to some Related questions that will aid in understanding this critter.

Answer 2

Positron emission occurs in a type of radioactive decay called beta plus decay. In this event, a proton in the nucleus of an atom undergoes a transformation and becomes a neutron. One of the up quarks of the proton becomes a down quark in this event, and a neutron appears where there was a proton. The event is mediated by the weak interaction (weak nuclear force), and a positron and a neutrino are ejected from the nucleus in the process. This is positron emission, or beta plus decay, and it is covered in other posts which are linked below.

Answer 3

A positron pair is two positrons. But they don't come in pairs. Positrons are created individually in beta plus decay. A positron could also appear with an electron. In that case, what appears is an electron-positron pair. That is a pair consisting of those two particles, and we see them appear in what is called pair production. Links to the related question about pair production and beta plus decay can be found below.