Sometimes referred to as the "God particle" because it seems to be everywhere, the Higgs boson is believed to give objects mass, but physicists armed with the world's most potent atom-smashers have yet to identify it.
Ever since it was first proposed in the 1960s, international physicists have endeavored to find the particle, and wondered what it might mean for scientific theory if it cannot be found.
In December 2011, scientists at the European Center for Nuclear Research announced "tantalizing hints" that the sought-after particle was hiding inside a narrow range of mass.
The clues came from CERN's Large Hadron Collider -- the world's largest atom-smasher, located along the French-Swiss border -- showing a likely range for the Higgs boson between 115 to 127 gigaelectronvolts.
US-based experiments echoed those findings, though in a slightly larger range.
On Monday, scientists working at the Fermi National Accelerator Laboratory (Fermilab) in the midwestern US state of Illinois will announce their latest Higgs search results based on data from Tevatron experiments there.