BUZZ — Ackman's Pershing Square slides after BofA downgrades stock
* Shares of Bill Ackman's Pershing Square slide 12% to $47.78 * BofA Global Research downgrades PS to "underperform" from "neutral"; slashes PT to $38 from $54, a 30% downside to last close * Brokerage says the underperformance of PS flagship funds delays further fundraises; expects asset manager to push back its ventu