fundamental_particles

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					Fundamental particles

The fundamental particles that make up our Universe can be divided into two main
categories:

(a) hadrons             these particles 'feel' the strong nuclear force
(b) non-hadrons         these particles do not 'feel' the strong nuclear force

These two main division are further divided as follows:

HADRONS
Mesons:  pions, kaons, eta mesons (composed of two quarks)
Baryons: protons, neutrons, omega, sigma, lambda particles (composed of three quarks)

NON-HADRONS
Leptons: electrons, muons, tauons, neutrinos

                Photons and gravitons

Note: At the present time gravitons are not known to exist.

Leptons are truly fundamental particles and cannot be broken down into smaller particles (as
far as we know!). However hadrons do have an internal structure being composed of true
fundamental particles called quarks.

(See: 16-19/Text/Nuclear physics/Nuclear structure/Quarks)


Some of the properties of these particles are shown in the following table.

         Particle          Symbol              Rest energy    Charge       Lifetime (s)
                                                 (MeV)
         LEPTONS
         Electron          e                      0.511       negative        stable
         Neutrino                             very small      zero          stable
         Muon                                   105.7       negative       2.2x10-6
         HADRONS           
         Mesons            
         Pion                                   139.6         +1         2.6x10-8
                           o                     135.0          0         0.8x10-16
         Kaon              K                        495
         Eta                                      549                          <10-18
         Baryons
         Proton            p                       938.3         1            stable
         Neutron           n                       939.6         0          650 (free)
         Lambda                                  1116          0           2.6x10-10
         Sigma             -                     1197          -1          1.6x10-10
                           o                     1192          0            6x10-20
         Omega                                   1672          -1          0.8x10-10

				
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posted:12/1/2011
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