Chris & Rihanna DATE NIGHT at Jay-Z Concert

Rihanna and Chris Brown aren't even trying to hide it anymore -- 'cause it looks like they were getting cozy at the Jay-Z concert tonight ... and, based on Twitter, everyone in Brooklyn saw it.

A pic taken from behind RiRi and Chris at Barclays Center is burning up the Internet -- they're seated in VIP ... he's on the left, she's on the right.

No physical contact -- in the photo, anyway -- but Chris' right arm is stretched around the back of Rihanna's chair.