Rihanna Makes Surprise MTV

Rihanna joined Jay-Z onstage Sunday night in Los Angeles to sing "Run This Town" and her Young Jeezy-assisted track "Hard." While it wasn't her first performance since she was assaulted by then-boyfriend Chris Brown in February, it did mark the first time she's performed any new material from the upcoming Rated R album.Rihanna told MTV News on Monday that she was ushering in a "new era" at the