"That is the biggest mismatch ever between theory and experiment in the history of physics, " Mr. Kaku admits, chuckling.

WSJ: The Weekend Interview with Michio Kaku: Captain Michio and the World of Tomorrow

The Higgs boson is the only particle theorized by the standard model of physics that hasn't been conclusively observed in an experiment.

WSJ: New Data Boosts Case for Higgs Boson Find

The AMS project began in 1994, when Professor Samuel Ting, a Nobel laureate from the Massachusetts Institute of Technology, was considering a new high-energy physics experiment.

ENGADGET: AMS detects excess of positrons, could suggest existence of dark matter