$$\require{cancel}$$
On the other side a electro-weak interaction is developed by Weinberg and Salam. A few years later ’t Hooft shows that it is a well-posed theory. This predicts the existence of three extremely heavy bosons that mediate the weak force: the $$Z^{0}$$ and the $$W^{\pm}$$. These have been found in 1983. There is one more particle predicted by these theories: the Higgs particle. Must be very heavy!