WASHINGTON — Several NBA teams had representatives at Capital One Arena on Tuesday night.

Among them were top executives for the Magic (Anthony Parker) and Clippers (Lawrence Frank). They came for Georgetown star freshman Thomas Sorber, a likely top 20 draft pick.

What they saw instead was as dominant a half as St. John’s has played this year, a 20-minute beatdown that was as thorough as it was ugly for the sparse home crowd.

Sorber was such a non-factor, it was easy to forget he was on the floor in the opening stanza.

The No. 15 Johnnies overwhelmed Georgetown so much, it didn’t matter that they didn’t perform very well offensively after halftime.

The Johnnies led by as many as 30 points in that first half, and were able to cruise to a 66-41 victory in the nation’s capital, registering their seventh straight win and 13th in 14 tries.

St. John’s completed a perfect January for the first time since the 1984-85 season. That was also the last time St. John’s started 9-1 in league play, this group’s current mark.

The Red Storm have won their past five contests despite their engine, Deivon Smith, being sidelined with a bruised right shoulder.

“That was the best defense/offense we’ve ever played [in a half],” coach Rick Pitino said. “The offense was just as brilliant as the defense, and we’re getting better and better.”

St. John’s (18-3, 9-1) defense was as stifling as it has been all year, holding Georgetown to 24.6 percent shooting from the field, forcing 16 turnovers and limiting the Hoyas (13-8, 4-6) to 16 points in the paint.

St. John’s had 12 steals and five blocked shots and moved up to fourth nationally in defensive efficiency, according to KenPom.com.

The 41 points were the fewest scored by Georgetown since 2012, and also the lowest total St. John’s has ever allowed in a league game.

“That was a defensive clinic that they just put on and they put a complete foot right in our ass,” Georgetown coach Ed Cooley said.

Kadary Richmond set the tone again, scoring 11 of his 13 points in the opening half, including a rare 3-pointer.

Zuby Ejiofor got the better of Sorber (eight points, nine rebounds), notching 13 points and eight rebounds, and Aaron Scott added 10 points and nine rebounds.

RJ Luis had 10 points, seven rebounds and four assists while Simeon Wilcher chipped in seven points, five assists and five steals.

It was 11-0, 23-3 and 41-11.

It was 47-21 at halftime, the second time in the past 25 years that St. John’s has led by more than 25 points at halftime against a Big East opponent.

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Two weeks ago, the two teams met at the Garden, and Georgetown raced out to a 14-point, first-half lead. St. John’s rallied to win, and made sure it didn’t dig itself another hole.

The Red Storm were ready for the Hoyas’ zone.

“We knew we had to pick up the energy the first four minutes, and that’s what we did,” Scott said. “We continued that throughout the first half.”

Those opening 20 minutes saw the Red Storm shoot 61.8 percent from the field, make 5 of 11 3-point attempts and pour in 26 points in the paint.

The second half was not as easy on the eyes.

Georgetown ratcheted up its intensity multiple levels and St. John’s kept turning the ball over.

The lead was trimmed to 15 at one point, but the Johnnies responded by finishing the game the way they started: By scoring 11 of the final 12 points.

“I think the best quality we have is that we’re humble. We just keep playing hard,” Pitino said. “We don’t think we’re great. We aspire to be great, but we don’t believe we’re great.

“We know Georgetown can beat us. We know [our next opponent] Providence can beat us. We know everyone can beat us. But we’re getting better and better and better, and that’s all we care about. Humility is a major factor.”