Wall Street ends lower as recovery momentum concerns spark sell-offWall Street lost ground on Thursday, with the S&P 500 and the Nasdaq pulling back from record closing highs in a broad sell-off driven by uncertainties surrounding the pace of the U.S. economic recovery. As the bond market rallied on a flight to safety, all three major U.S. stock indexes tumbled. The Dow's economically sensitive transports plunged 3.3%, its biggest daily drop since October.