The exchange particle of the electroweak force is the photon. It couples to particles with an electromagnetic charge. This charge can either be positive or negative. The exchange particle of the strong force, the gluon, couples just like the to particles that carry a so called color charge.
Today we want to experimentally determine the number of possible color charges (or simply colors) with data of the Belle II experiment.
To that end we should first approach the subject from the theoretical side. To start with we
should take a look at the so called R-value.
After that we’re ready to look at the experimental measurement, to determine the number of color charges.