Two years ago I
discussed the results of a very interesting search performed by the CDF experiment in its dataset of 2-TeV proton-antiproton collisions, provided by the Tevatron accelerator at Fermilab.
The search focused on the hypothesis that a massive fourth-generation quark was produced in the collisions. What was assumed was that the quark was heavy -otherwise previous searches would have found it already-, and that it behaved similarly to the sixth quark, the top, which is by now a well-known animal of the particle zoo.