Phys. Rev. Lett. 101, 171805 (2008) doi:10.1103/PhysRevLett.101.171805

The top quark is roughly 40 times as massive as the second heaviest quark, the bottom. But why?

Hsin-Chia Cheng and his colleagues at the University of California, Davis, propose that top quarks may have a 'superpartner' with a spin of 1 rather than spin 0 as is usually predicted by supersymmetry theory. Spin-1 particles tend to mediate forces; the photon, for example, is a spin-1 particle and is responsible for electromagnetism. The new particle, the researchers propose, would mediate a force determining the interaction of the top quark with the Higgs boson, which putatively gives things mass.

If such a particle were to exist, it should be detectable with the Large Hadron Collider, when that is back in action.