"Cam definitely set the tone we wanted early with his intensity inside," Barnes said.
Texas gave up a double-digit lead in a home loss to Kansas a week earlier, but was in total control of the Red Raiders just a few minutes after halftime. Lewis scored five in a row and swished a 3-pointer that put Texas ahead 42-26.
Texas forced the Red Raiders into 19 turnovers and converted them into 22 points.
"It's basically impossible to win like that," Texas Tech interim coach Chris Walker said.
He added: "Texas has lost some tough games. You can't look at their record. They played some tough teams. They're a bunch of young guys."
Texas Tech cut the lead to 52-44 on a 3-pointer by Jaye Crockett with just over seven minutes left but never threatened again. The Longhorns scored five straight points, including a 3-pointer by Papapetrou, to end the rally.
"We haven't responded the way we've liked, but tonight we did," Barnes said. "We haven't harped on (the losing) as much as we've harped on why we're not winning. I don't think these guys ever thought they weren't good enough."