(Reuters) - European shares had their worst session in more than six weeks on Thursday after the U.S. Federal Reserve dampened rate cut bets, while gains by Volkswagen and Bayer helped cap losses. The pan-European STOXX 600 index fell 0.7 percent with most major country indices well in the red on returning from the May Day holiday.Germany's DAX, which outperformed through most of the day, closed flat as software firm SAP weighed. Madrid's IBEX fell 1.6 percent. U.S. Fed Chairman Jerome Powell..