Fermilab believed they hit the motherlode this past April after findings from the Tevatron particle accelerator suggested a new subatomic particle was out there. A second, independent group has analyzed that same data and claim there is no new particle.
The research team DZero has a detector of their own in a different section of the Tevatron, and have been poring over their own data from the same experiments. Originally, Fermilab pointed to a "bump" in energy levels that was inconsistent with expected behavior for particles involved in the experiment. DZero says that bump didn't exist in their findings.
One of the earliest theories attempting to explain this discrepancy is how the experiment was modeled. If the analytical equations were off from the start, then it would provide faulty results. DZero considers this a possibility. Fermilab thinks there's not much of a difference between the two sets of results, but they have yet to read DZero's paper.
The ultimate decider of this debate will likely be the Large Hadron Collider. Many in the science community expect the experiment to be replicated on the larger proton accelerator, which could provide definitive results anywhere between the next 3-18 months. [New Scientist via Slashdot]