Interactions and fields Particle Physics The colour wavefunctions of the gluons can in general be linear combinations of these states and the totally symmetric combination R R + G G + B B is a colour singlet, i.e. it is colourless, and therefore plays no part in the strong interactions. Thus in contrast to the electromagnetic case which there is only one type of field quantum, the photon, there are eight coloured gluons. Furthermore since the gluons themselves are coloured they can couple to each other and the Feynman diagrams for colour interactions may contain triple gluon vertices as shown in figure 11.
Fig 11: A quark-quark interaction showing three gluon coupling. Dayalbagh Educational Institute
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