NEW YORK, Oct 20 (Reuters) - Shares of Corrections Corp jumped more than 6 percent on Tuesday following news that Pershing Square Capital Management, headed by activist value investor William Ackman, had made an investment in the prison manager. Ackman said at an investor conference the stock was "cheap" and was worth between $40 and $54 per share. For details, see The stock jumped as high as $26.17 -- an intraday session high -- following Ackman's comments.