NEW ORLEANS (Reuters) - The National Football League was still working with New Orleans officials on Monday to determine what caused the power outage at Sunday's Super Bowl at the Superdome, so far dismissing any connection with the Beyonce halftime show. With a record U.S. television audience watching along with viewers in 180 countries, about half the stadium lights went dark early in the second half of the game, in which the Baltimore Ravens defeated the San Francisco 49ers, 34-31. ...