The unbeaten Badgers opened their Big Ten season by outscoring the Wildcats 40-14 during the first 20 minutes.
Northwestern went just 6-of-26 from the field in the first half and made only 1-of-10 from 3-point range.
Wisconsin improved to 14-0 for the season with an easy road win, one in which the Badgers shot 55 percent from the field and turned the ball over a mere four times. They are one of two Big Ten teams to reach the conference portion of their schedule unbeaten, joining Ohio State with a perfect record.
Hayes made 8-of-12 from the field and grabbed six rebounds. Sam Dekker added 15 points and eight boards for the Badgers.
Alex Olah was a bright spot Northwestern, scoring 23 while hitting 10-of-14 shots.