Jay-Z celebrates Flatiron's 40/40 club relaunch

New dad Jay-Z didn't let a little thing called a newborn child stop him from celebrating the relaunch of his sporty-luxe Flatiron District club 40/40 on Wednesday.

Arriving around 11 p.m., the new dad worked the room, greeting guests and mingling. Despite rumors, wife Beyonce, understandably, was a no-show, though her music was played in heavy roation by the night's DJ, according to sources.

Guests included Swizz Beatz (sans wife Alicia Keys), CC Sabathia, Alex Rodriguez, Fabolous, Ashanti, Selita Ebanks and gazillionaire Warren Buffett, whom Jay-Z palled around with (above) before ducking out at 2 a.m.