Although we seem to live in three spatial dimensions, physicists study the possibility of other dimensions which are hidden because they are too small to see. "Particularly interesting are the so-called universal extra dimensions, in which all known particles can propagate," said Fermilab theoretical physicist Bogdan Dobrescu. "If universal extra dimensions exist, then for each of the elementary particles we know, there would be a whole family of heavier particles with similar properties, called Kaluza-Klein modes."
New predictions for the experimental signatures of universal extra dimensions have been made this week in a paper titled "Resonances from Two Universal Extra Dimensions," which is now available on the hep-ph archive . Dobrescu authored the study with two former Fermilab postdocs, Gustavo Burdman (University of Sao Paulo in Brazil) and Eduardo Ponton (Columbia University). They spent more than a year computing the masses of these Kaluza-Klein modes and all their interactions. The researchers predict that when these heavier particles decay, they produce a very specific signal: a top quark and an anti-top quark, with energies matching the mass of the Kaluza-Klein mode.
"It's interesting that now, ten years after the top quark discovery, we find that the top quark is a great tool in the search for something as exciting as extra dimensions," said Dobrescu. "Two universal extra dimensions would explain certain basic facts about nature, including the stability of the proton, the origin of dark matter, and the existence of three 'generations' of quarks and leptons." Dobrescu points out that this is a particularly thrilling time at Fermilab. "Our wild theoretical ideas about physics at the energy frontier are just about to be tested experimentally by the DZero and CDF collaboration," he said. Dobrescu, who was promoted to Scientist I in October 2005, anticipates that the Large Hadron Collider (LHC) scheduled to begin operation at CERN in 2007 will further test the existence of extra dimensions.