As the universe expanded and cooled, interactions became less energetic and when the universe was about 10−12 seconds old, W and Z bosons ceased to be created at observable rates. The remaining W and Z bosons decayed quickly, and the weak interaction became a short-range force in the following quark epoch.
As the universe expanded and cooled, interactions became less energetic, and by about 10−12 seconds old, the production of W and Z bosons slowed down. The remaining W and Z bosons then decayed rapidly, leading to the weak interaction becoming a more confined force in the following epoch.