What decides electric charge of a particle? A proton has 3 quarks (up,up,down) we know that according to charge of those quarks decides the charge of proton but what decides charge of those quarks? not only quarks every particles in standard model? how do they create their own electromagnetic field? what creates their field?
what decides charge of those quarks? not only quarks every particles in standard model
Nature, or "the way the cookie crumbled" when the universe appeared.
The standard model is an encapsulation of an enormous amount of data, (measurements). It describes practically all particle interactions and is very predictive, as the recent LHC experiments showed. The SU(3)xSU(2)xU(1) symmetry of the standard model is where the quarks and leptons have a niche in the representations, and is a minimal way of ordering all this plethora of data.
It is analogous to mathematical axioms. A physics theory has a number of "axioms" on which it depends, which connect the mathematics to the physical measurements. One of these "axioms" is the particle table of the standard model. More complex "particles" appear according to strict conservation laws, including charge and quantum numbers.