MILAN (Reuters) - The tiny pearl brooch seems an innocuous detail in Raphael's enigmatic "Fornarina" portrait, but for one group of historians it unlocks a scandalous love affair kept secret for centuries. According to new research published in May, the pearl, pinned onto an elaborate turban, is part of a web of allusions to the Renaissance artist's clandestine marriage to the beautiful sitter, a baker's daughter -- despite a very public engagement to the niece of a powerful Vatican cardinal. Officially, Raphael died a bachelor at 37. "It was an impossible love affair," says Maurizio Bernardelli Curuz, editor of specialist...