The Standard Model In the Standard Model the most important parameters are:

• The coupling constants which determine the strength of the interaction
• The properties of the mediators of the forces - the photon, the gluon, the W and the Z particle
• The properties of the quarks and leptons

These properties depend on each other and the relations are given by the Standard Model. A determination of the way the Z and W particles decay are important inputs to the model. Measuring very accurately the mass and different decay properties of the Z and the W particles it was possible to determine the top mass several years before it was actually directly observed.
Precision measurement at LEP of the Standard Model parameters also give valuable information about the hypothetical Higgs particle, which is believed to be the particle responsible for giving the Z and W particles and also the quarks and leptons their masses. The question of mass is however still one of the great mysteries in Nature.