Natural Science Forum / Physics / Particle Physics / September 2006

I think originally the quarks were assigned +,- 1 values of charge but
that violated the Pauli exclusion principle.  So a trialility scheme was
devised.  Which also ended up matching experimental evidence in DIS at
SLAC.

Griffiths' "Introduction to Elementary Particles".

FrediFizzx

Quantum Vacuum Charge papers;
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps
http://www.arxiv.org/abs/physics/0601110
http://www.vacuum-physics.com

Quantum Ranger schrieb:

At the beginning of the 60ers, Gell-Mann had detected the eightfold way
http://en.wikipedia.org/wiki/Eightfold_way_%28physics%29

He had represented the observed hadrons - classified into groups
according to their spin - as points in a coordinate system where some
quantum numbers were used as axes. Doing this, Gell-Mann had observed
that these particles arrange as patterns which were already known in
mathematics as representations of the group SU(3). This way, Gell-Mann
noticed that one of the patterns had been incomplete. In fact, he could
predict the existence of an additional particle (the missing one( which
could be found later.
However, the most peculiar thing was that the most fundamental
presentation of that group SU(3) was missing in nature. So he
postulated its existence. It consists of 3 particles called quarks
which combine to build the observed hadrons.
SInce the charges of 3 of them (as dictated by SU(3)) have to add up to
result in the charges of the baryons (proton, neutron etc.), the
charges
up : +2/3
down: -1/3
strange:-1/3
are a most natural choice.
This way you can build the neutral neutron as (up, down, down) and the
positive proton as (up, up, down) and the charges of all other hadrons
consistently.
A bit of the history is given in the link above.