Justin Bieber [VIDEO] ALL SMILES After Alleged Baby Mama Exposed

11/17/2011 11:35 AM PST

Justin Bieber -- All Smiles After Alleged Baby Mama Exposed

Justin Bieber
looks like a guy without a care kid in the world ... smiling and posing with fans today in New York.

Bieber was on his way out of a radio station -- and even though people were firing off questions about his alleged baby mama Mariah Yeater, dude didn't seem to be bothered one bit.

Makes sense ... considering Yeater's looking more and more like a TOTAL FRAUD.

TMZ broke the story ... Yeater dismissed her lawsuit against Biebs last week ... and now, new text messages appear to show that she conspired to conceal any evidence that her ex-BF is the REAL baby daddy.