A mission to the Syrian Desert by U.N. nuclear sleuths to examine a building flattened by Israeli warplanes could open a new front in the search for rogue nations trying to develop atomic arms under the radar of the international community. It is a low-key endeavor: Only four International Atomic Energy Agency inspectors will participate in the three-day project starting Sunday, and both Damascus and the U.N. agency have pulled down the blinds on news media seeking to report on the trip, keeping all details secret. Washington hopes that the U.N agency team will come back with persuasive evidence backing U.S. intelligence that the structure hit by the Israel in September was a nearly completed plutonium-producing reactor.