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Welcome to our Physics lesson on Mesons and Anti-mesons, this is the first lesson of our suite of physics lessons covering the topic of Particles and Antiparticles - Interaction and Laws of Conservation, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
In the previous tutorial, we explained that muons and pions (both considered as mesons as their mass is in-between the mass of electron and nucleons) were identified and discovered in cosmic rays. The electric charge of muons and pions is the same as that of electron. The two types of muons (μ+ and μ- are antiparticles of each other. Each of them has a spin of 1/2 and a mass of 106 me = 54 MeV/c2.
Muons are unstable particles; their lifespan is 2.2 microseconds approximately. Muons transform into an electron (positron), a neutrino and an antineutrino according the scheme shown below:
and
As for pions, there are three types of pions, all of them having a zero spin. Two of them, π+ and π- have equal mass (273 me or 140 MeV/c2). These particles are also unstable; their lifespan is 26 nanoseconds (about 85 times shorter than the lifespan of muons).
The three possible reactions in which a pion splits in two other elementary particles are:
It is worth remembering that μ- and π- are the mesons while μ+ and π+ are their corresponding anti-mesons.
You have reached the end of Physics lesson 21.2.1 Mesons and Anti-mesons. There are 6 lessons in this physics tutorial covering Particles and Antiparticles - Interaction and Laws of Conservation, you can access all the lessons from this tutorial below.
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