Pfizer PFE.N, Starbucks SBUX.O and ConocoPhillips COP.N are among the reports due this week. By Lewis Krauskopf NEW YORK, May 2 (Reuters) - Mixed financial results from U.S. megacap companies are dampening an otherwise better-than-expected first-quarter earnings season and so far failing to fuel stock performance in the face of U.S. Federal Reserve monetary tightening. Concerns over surging inflation and how aggressively the Fed plans to act to rein it in along with geopolitical worries such as the war in Ukraine and lockdowns in China continue to hang over the market, investors said.