U.S. Stocks Mixed Ahead of ECB Meeting; Investors Await Apple Event

U.S. stocks turned mixed Wednesday, as investors gear up for a key policy meeting from the European Central Bank on Thursday. Analysts don't expect the central bank to increase its monthly pace of asset purchases. Meanwhile, Apple (AAPL) - Get Report is holding an event in California on Wednesday where the iPhone 7 is expected to be introduced. Analysts also expect the unveiling of a new version of the Apple Watch. Chipotle (CMG) - Get Report shares rose almost 5 percent after billionaire investor Bill Ackman's hedge fund, Pershing Square, revealed a 9.9 percent stake in the restaurant chain, according to a filing. TheStreet's Scott Gamm reports from Wall Street.