Actor Ashton Kutcher said on Friday that Mischa Barton, The O.C. star who was hospitalized last week for psychiatric observation, is “doing great” and headed for New York to join the cast of a TV show. Kutcher talked briefly about Barton at a technology conference in Pasadena, which the actor and producer attended to discuss his use of the social networking website Twitter. “I can tell you right now Mischa Barton is doing great,” said Kutcher, who is the creator of a television show called The Beautiful Life that features Barton. The show, which airs on The CW network in the fall, is about a group of models, and Barton plays a beauty with a pill-popping habit.