Classification of subatomic particles

[*hailey*]

How are subatomic particles classified into the following:

1. Leptons

2. Mesons &

3. Baryons ?

[imatfaal]

There are multiple layers of classification

Most basic, I guess, is between fermions (half integer spin) and bosons (integer spin)

The bosons are subdivided at a fundamental level into the spin 1 gauge bosons (which moderate the strong, electromagnetic and weak force), the spin 0 Higgs Boson (which is linked to mass), and the hypothetical spin 2 graviton (which should be the boson for gravity).

 

The fermions are divided into two groups at this fundamental level - the quarks which are charged, massive, never exist by them selves and in come in different flavours (getting heavier the flavours are - up down, strange charm, bottom top) and the leptons. The leptons are the electron, and its two bigger brothers the muon and the tau (in ascending mass and all with -1 charge) - each of these has a pair neutrino (which is almost massless and no charge) the electon neutrino, the muon neutrino, and the tau neutrino.

 

All of these fermion particles also have anti-matter pairs - so there is an anti-neutrino, an top antiquark etc.

 

If you get a quark and an anti-quark together in a particle - we call this a meson. The longest lived is for fractions of a millisecond. You get mesons which are the pair of same flavour, or a pair of different flavours, and even odd quantum mechanical nonsense where one particle is kinda mixture of two pairs.

 

If you get three quarks togehter in a particle we call this a baryon. If you have two up quarks (+2/3 charge each) and one down quark (-1/3 charge) you get a proton (+1 charge). If you have two down ( -1/3 each) and one up (+2/3) you get a neutron (no charge). All normal matter is made up of protons, neutrons and electrons.

 

So from the fundemental and compostite versions of fermions we get the matter particles which we can find in nature and the lab - ie we have lightest (from greek for light) - the leptons, the middle ones(from greek for in between) the mesons, and the heaviest (from the greek for heavy) the baryons.

By MissMJ [CC BY 3.0 http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons(

[*hailey*]

Thank you so much

[pavelcherepan]

Thanks, umatfaal, great explanation. Quick question though - I take it that quarks and antiquarks don't annihilate like other particle-antiparticle pairs do? Is there a different meaning of matter-antimatter when you're dealing with quarks?

[ajb]

Is there a different meaning of matter-antimatter when you're dealing with quarks?

You have to take the colour charge and flavour into account along with the electric charge when considering annihilations.