In late April, lawyers for [Steven A.] Cohen and his firm met with federal prosecutors in Manhattan to make their best case argument about why the hedge fund billionaire and his SAC Capital Advisors should not be charged with criminal wrongdoing. But people familiar with that meeting said the lengthy presentation did not impress federal prosecutors, who are now considering whether to use a racketeering law aimed at prosecuting the Mafia and drug gangs to pursue a criminal case against Cohen’s hedge fund.