In theoretical physics, which particle has the symbol (upper-case) G?
In theoretical physics, the graviton, with symbol upper-case G, is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory.
The gluon, with symbol lower-case g, is an elementary particle that acts as an exchange particle for the strong force between quarks: it 'glues' quarks together, forming protons and neutrons.
A gauge boson is a force carrier, a bosonic particle that carries any of the fundamental interactions of nature, commonly called forces.
The gravitino, with symbol G͂ (upper-case G-tilde), is the supersymmetric partner of the hypothesized graviton. It has been suggested as a candidate for dark matter.
More Info:
en.wikipedia.org