The Wildcats lost for only the second time this season, both coming in Pacific-12 Conference play, and UCLA moved into second place by itself in the league chase. Oregon sits on top of the conference with a 6-0 record.
The Bruins opened a 21-5 lead over the first eight minutes, held a 10-point advantage at halftime and allowed Arizona no closer than five points during the second period.
Muhammad scored 23 points and Jordan Adams added 15 for the Bruins (16-4, 6-1 Pac-12).
Arizona shot just 38 percent from the field and went 5-of-24 from 3-point range. The Wildcats (16-2, 4-2) were led by Nick Johnson with 23 points and Mark Lyons with 16.
The other Arizona loss came against Oregon by four points on Jan. 10 after the Wildcats had won their first 14 games of the season.