Nick Johnson scored 16 points as the Wildcats dominated the second half against the Buffaloes in the semifinals of the Pac-12 tournament in Las Vegas.

T.J. McConnell had 12 points and five assists for top-seeded Arizona (30-3), which advanced to face No. 2 seed UCLA in Saturday’s championship game. The Wildcats held the fifth-seeded Buffaloes to 29.4 percent shooting and have won their first two tournament games by an average of 26 points.

Askia Booker paced Colorado (23-11) with 12 points while Xavier Johnson had 11 points and five rebounds. The Buffaloes, who lost all three meetings against the Wildcats this season, were outscored 36-19 in the second half and trailed by as many as 19 with eight minutes remaining.

The first half featured five ties and ended with Arizona taking a 27-24 lead on Gabe York’s 3-pointer at the buzzer before the Wildcats quickly took control. Colorado missed 11 of its first 13 shots in the second half, and Arizona used a 22-6 run to move ahead 51-32 with just under eight minutes to play.

Arizona, which outrebounded the Buffaloes 41-25, turned in its second straight dominant defensive performance after holding Utah to 12 field goals in Thursday’s 71-39 quarterfinal victory. Rondae Hollis-Jefferson had 12 points and eight rebounds and Aaron Gordon collected nine points and nine boards for the Wildcats, who won despite shooting 6-of-17 from 3-point range.

GAME NOTEBOOK: Arizona defeated UCLA 79-75 at home on Jan. 9 and won both meetings against Stanford this season. … Colorado was held to less than 50 points for the first time since last season’s 57-49 loss to Illinois in the second round of the NCAA tournament. … Booker and Johnson combined to shoot 8-of-25 from the field for the Buffaloes, who were facing Arizona in the Pac-12 tournament for the third straight year.